Lets verify what we are seeing. In response to Arun Nair. To find information about ip basic bgp configuration # config router bgp set as 65100 set router-id 172.16.1.3 config neighbor edit "10.3.1.254" set remote-as 65200 next end config network edit 1 set prefix 10.1.0.0 255.255.255. protocol redistribution . If no backdoor link exists between sites in the same area, you do not need to configure any OSPF sham link. --Border Gateway Protocol. To locate and download MIBs for selected platforms, Cisco IOS XE releases, and feature sets, use Cisco MIB Locator found at the following URL: Application of the Border Gateway Protocol in the Internet. 1. No new or modified RFCs are supported by this feature. An error occurred when loading the video. Emerging industry standard upon which tag switching is based. Router1(config-if)# area area-id sham-link source-address destination-address cost number, 17. vrf --provider edge router. configure VPNv4 peering between PE routers. When OSPF routes are propagated over the MPLS VPN backbone, additional information about the prefix in the form of BGP extended communities (route type, domain ID extended communities) is appended to the BGP update. Figure 4-53 Networking diagram for configuring an OSPF sham link Configuration Roadmap The configuration roadmap is as follows: Establish an ME-IBGP peer relationship between the PEs and configure OSPF between the PEs and CEs. OSPF has a lower administrative distance (AD) than internal BGP (BGP running between routers in the same autonomous system). What is MPLS Label distributing protocol (LDP) ? These customer edge (CE) routing devices are linked together by a Layer 3 VPN over Router PE1 and Router PE2. This video demonstrates configuration a DMVPN Hub and Spoke in Phase 3 Configuration.It confirms Phase 3 connectivity between 2 Spokes and Hub to Spoke Conf. The Sham-link Endpoint Address must be advertised by BGP as VPN-IPv4 address; it must NOT be advertised by OSPF. If a prefix is learned across the sham-link and the path via the sham-link is selected as the best, the PE router does not generate an MP-BGP update for the prefix. If the backdoor links between sites are used only for backup purposes and do not participate in the VPN service, then the default route selection shown in the preceding example is not acceptable. --Open Shortest Path First protocol. CE 1 and CE 2 are in the same OSPF area. . 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks, C 10.0.0.0/8 is directly connected, FastEthernet0/0, L 10.1.1.1/32 is directly connected, FastEthernet0/0, B 30.0.0.0/8 [200/0] via 192.168.30.1, 00:05:57, O 192.168.40.1 [110/2] via 10.1.1.2, 00:40:55, FastEthernet0/0, B 192.168.50.1 [200/2] via 192.168.30.1, 00:05:57, B 30.0.0.0/8 [200/0] via 192.168.30.1, 00:06:24, B 192.168.50.1 [200/2] via 192.168.30.1, 00:06:24. PE To obtain better user experience, upgrade the browser to the latest version. router -- Configure router1 and router 3 in area 0 to ensure that OSPF routes learned other end should prefer MPLS backbone. All VPN processing occurs in the PE router. The OSPF sham-link is used only to influence intra-area path selection. area Method Status ProtocolFastEthernet0/0 10.1.1.1 YES manual up upSerial4/0 1.1.1.1 YES manual up upSerial4/2 3.3.3.2 YES manual up upLoopback0 192.168.10.1 YES manual up upLoopback1 192.168.11.1 YES manual up upLoopback2 192.168.12.1 YES manual up upLoopback3 192.168.13.1 YES manual up up, Interface IP-Address OK? OSPF Sham Link The only way to fix this is to advertise the routes that are learned through the MPLS VPN network as intra-area routes. undo arp learning passive enable Passive ARP. IGP OSPF Sham links is a logical inter-area link carried by the super backbone. When OSPF is used as a protocol between PE and CE routers, the OSPF metric is preserved when routes are advertised over the VPN backbone. arp learning passive enable Passive ARPVRRPBackupIPIPARPARP. The metric is used on the remote PE routers to select the correct route. Step 9: area area-id sham-link source-address destination-address authentication key-chain chain-name. As shown in Figure 4-53, CE1 and CE2 belong to the same OSPF area of VPN1 and they connect to PE1 and PE2 respectively. When sending traffic to a particular destination, the PE router uses the MP-BGP forwarding information. To create a sham-link, use the following commands starting in EXEC mode: 2. ospf Router1(config)# When a sham-link is configured between PE routers, the PEs can populate the VRF routing table with the OSPF routes learned over the sham-link. The following example shows the forwarding that occurs between sites from the standpoint of how PE-1 views the 10.3.1.7/32 prefix, the loopback1 interface of the Winchester CE router in the figure above. cost make sure both the CEs routers able to ping. To begin, MPLS is set up in the network as shown with R2 and R4 acting as Provider Edge (PE) routers, and MPLS is enabled throughout R2-R3-R4. We are using OSPF process 2 inside provider backbone and OSPF process 1 is being used between the CE and PE. Each task in the list is identified as either required or optional. This prefix is the loopback interface of the Winchester CE router. address Router1(config-if)# ip vrf forwarding vrf-name, 6. configures the OSPF cost for sending an IP packet on the PE-2 sham-link BGP release notes for your platform and software release. --Border Gateway Protocol. Removes the IP address. When the backdoor link is not enabled between the CE1 and CE2 the path followed from CE1 to CE2 is via MPLS backbone as shown below , Last update from 9.9.12.2 on FastEthernet0/0, 00:00:10 ago, * 9.9.12.2, from 9.9.12.2, 00:00:10 ago, via FastEthernet0/0 #Known via R2#, Route metric is 3, traffic share count is 1, VRF info: (vrf in name/id, vrf out name/id), 2 9.9.23.3 [MPLS: Labels 17/16 Exp 0] 96 msec 56 msec 76 msec, 3 9.9.45.4 [MPLS: Label 16 Exp 0] 84 msec 80 msec 56 msec. It allows you to create a point-to-point connection between the two PE routers. Configure VPN instances on PEs and bind the interfaces connected to CEs to the VPN instances. This module describes how to configure and use a sham-link to connect Virtual Private Network (VPN) client sites that run the Open Shortest Path First (OSPF) protocol and share backdoor OSPF links in a Multiprotocol Label Switching (MPLS) VPN configuration. The sham link is an unnumbered point-to-point link inside a routing-instance between two PE routers. Router1(config-if)# loopback -- Router1(config)# may not support all the features documented in this module. enters interface configuration mode. forwarding --customer edge router. To verify that the sham-link was successfully created and is operational, use the show ip ospf sham-links command in EXEC mode: Displays the operational status of all sham-links configured for a router. In an MPLS VPN configuration, the OSPF protocol is one way you can connect customer edge (CE) routers to service provider edge (PE) routers in the VPN backbone. Configures In an MPLS VPN configuration, the OSPF cost configured with a sham-link allows you to decide if OSPF client site traffic will be routed over a backdoor link or through the VPN backbone. A sham-link ensures that OSPF client sites that share a backdoor link can communicate over the MPLS VPN backbone and participate in VPN services. The PE router uses the information received from MP-BGP to set the ongoing label stack of incoming packets, and to decide to which egress PE router to label switch the packets. cost number configures the OSPF cost for sending an IP packet on the PE-2 sham-link interface. A VPN client has three sites, each with a backdoor link. When sending traffic to a particular destination, the PE router uses the MP-BGP forwarding information. They are deployed in cases when areas become partitioned or an area does not border Area 0. It is defined in RFC 1163. Use these resources to familiarize yourself with the community: What is OSPF Sham Links? OSPF Bug Search Tool and the OSPF is often used by customers that run OSPF as their intrasite routing protocol, subscribe to a VPN service, and want to exchange routing information between their sites using OSPF (during migration or on a permanent basis) over an MPLS VPN backbone. By using OPSFsham-linka virtual link is created between the two PEs allowing them to appear as a point-point link between OSPF. After the configuration is complete, PE1 and PE2 can learn the route to the loopback interface of each other and establish an MP-IBGP peer relationship. The reason the OSPF route is not redistributed to BGP on the PE is because the other end of the sham-link already redistributed the route to BGP and there is no need for duplication. Configure < Return to Cisco.com search results. vrf Configure one loopback each on PE1 & PE2 and make it member of VRF. Sham Linkcan be created using two loopbacks on the respective devices advertised into the BGP address family that corresponds with the customerVRF. The information displayed on CE1 is used as an example. ip For a sham link to be active, two conditions must be met: src-address is a valid local address with /32 netmask in OSPF instance's routing table. Because the sham-link is seen as an intra-area link between PE routers, an OSPF adjacency is created and database exchange (for the particular OSPF process) occurs across the link. Reconfigures To find information about Configures the specified OSPF process with the VRF associated with the sham-link interface on PE-1 and enters interface configuration mode. OSPF SHAM LINK. Unless noted otherwise, subsequent releases of that software release train also support that feature. Perform the following steps on the PE devices at both ends of a sham link. DoNotAge LSA allowed. sham-links. LSA When OSPF is used as a protocol between PE and CE routers, the OSPF metric is preserved when routes are advertised over the VPN backbone. Enters global Configuring OSPF sham links Network requirements As shown in Figure 46: CE 1 and CE 2 belong to VPN 1 and are connected to PE 1 and PE 2, respectively. Although OSPF PE-CE connections assume that the only path between two client sites is across the MPLS VPN backbone, backdoor paths between VPN sites (shown in grey in the figure below) may exist. Cisco IOS software is packaged in feature sets that support specific platforms. Router1# --customer edge router. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. We can do this with the OSPF sham link. A Sham links is required only between two VPN sites that belong to the same area and have a backdoor link for backup purposes. When OSPF routes are propagated over theMPLS VPNbackbone, additional information about the prefix in the form of BGP extended communities (route type, domain ID extended communities) is appended to the BGP update. PWE3 Carrying Enterprise Leased Line Services on a MAN, Licensing Requirements and Limitations for PWE3, (Optional) Creating a PW Template and Setting Attributes for the PW Template, Enabling the Device to Send BFD for PW Packets, Verifying the Configuration of Static BFD for PWs, Verifying the Configuration of Dynamic BFD for PWs, Configuring PW Redundancy in a Scenario Where CEs Are Asymmetrically Connected to PEs, Configuring BFD to Detect Public Network Links, Negotiating the Primary/Secondary Status of a PW, Verifying the PW Redundancy Configuration, Example for Configuring a Dynamic Single-hop PW, Example for Configuring a Static Multi-hop PW, Example for Configuring a Dynamic Multi-hop PW, Example for Configuring a Mixed Multi-hop PW, Example for Configuring Static BFD for PWs, Example for Configuring Dynamic BFD for a Single-hop PW, Example for Configuring Dynamic BFD for a Multi-hop PW, Example for Configuring Inter-AS PWE3-Option A, Example for Configuring PW Redundancy in a Scenario Where CEs Are Asymmetrically Connected to PEs, Interworking Between LDP VPLS and BGP AD VPLS, Licensing Requirements and Limitations for VPLS, Creating a VSI and Configuring LDP Signaling, Enabling the BGP Peer to Exchange VPLS Information, Creating a VSI and Configuring BGP Signaling, (Optional) Configuring Huawei Devices to Communicate with Non-Huawei Devices, (Optional) Configuring the Features of Kompella VPLS, Verifying the Kompella VPLS Configuration, Enabling BGP Peers to Exchange VPLS Information, Creating VSIs and Configuring the BGP AD Signaling, (Optional) Resetting BGP Connections for L2VPN-AD, Configuring Interworking Between LDP VPLS and BGP AD VPLS, Configuring Static VLLs to Access a VPLS Network, Configuring the Static LSP Between the UPE and the SPE, Configuring a UPE to Access an SPE Through a Static VLL, Verifying the Configuration of Static VLLs to Access a VPLS Network, Creating VSIs and Configuring the BGP Signaling, Configuring the Multi-Homed Preference for a VSI, Verifying the Configuration of CE Dual-Homed Kompella VPLS, Configuring Inter-AS Martini VPLS in Option A Mode, Configuring Inter-AS Kompella VPLS in OptionA Mode, (Optional) Associating Spoke PW Status with Hub PW Status, (Optional) Manually Switching PWs in a PW Protection Group, Verifying the VPLS PW Redundancy Configuration, Configuring a VSI to Ignore the AC Status, Configuring VSI-based Traffic Suppression, Verifying the Consistency of VPN Configurations (Service Ping), Verifying the MAC Address Learning Capability, Verifying Connectivity of the VPLS Network, Configuring the Upper and Lower Alarm Thresholds for VPLS VCs, Verifying MPLS L2VPN Specifications and Usage Information, Example for Configuring VPLS over TE in Martini Mode, Example for Configuring VPLS over TE in Kompella Mode, Example for Configuring Interworking Between LDP VPLS and BGP AD VPLS in HVPLS Mode, Example for Configuring Static VLLs to Access a VPLS Network, Example for Configuring Dynamic VLLs to Access a VPLS Network, Example for Configuring CE Dual-Homed Kompella VPLS, Example for Configuring Inter-AS Martini VPLS in OptionA Mode, Example for Configuring Inter-AS Kompella VPLS in OptionA Mode, L2VPN Access to L3VPN Supported by the Switch, Application Scenarios for L2VPN Access to L3VPN, VLL Access to the Public Network or L3VPN, VPLS Access to the Public Network or L3VPN, Licensing Requirements and Limitations for L2VPN Access to L3VPN, Configuring VLL Access to the Public Network or L3VPN, Associating the L2VE Interface with a VLL, Configuring User Access to the Public Network or L3VPN, Verifying the Configuration of VLL Access to the Public Network or L3VPN, Configuring VPLS Access to the Public Network or L3VPN, Verifying the Configuration of VPLS Access to the Public Network or L3VPN, Configuration Examples for L2VPN Access to L3VPN, Example for Configuring VLL Access to L3VPN. display ospf sham-link; display ospf spf-statistics; display ospf statistics updated-lsa; display ospf vlink; dn-bit-set; dn-bit-check; domain-idOSPF . For basic information about how to configure an MPLS VPN, refer to the "MPLS Virtual Private Networks Configuration" module. sham-link between PE routers in an MPLS VPN, you must: You can use the /32 That is, the VPN traffic Cost of using 1 State POINT_TO_POINT. Because each site runs OSPF within the same Area 1 configuration, all routing between the three sites follows the intraarea path across the backdoor links, rather than over the MPLS VPN backbone. Using Distribute-List, OSPF Limit on Number of Redistributed Routes, OSPFv3 Fast Convergence: LSA and SPF Throttling, OSPF Support for Unlimited Software VRFs per PE Router, OSPF Link-State Database Overload Protection, OSPF MIB Support of RFC 1850 and Latest Extensions, Configuring OSPF TTL Security Check and OSPF Graceful Shutdown, OSPF SNMP ifIndex Value for Interface ID in Data Fields, OSPF Support for Forwarding Adjacencies over MPLS TE Tunnels, OSPF IPv4 Remote Loop-Free Alternate IP Fast Reroute, Prerequisites for OSPF Sham-Link Support for MPLS VPN, Restrictions on OSPF Sham-Link Support for MPLS VPN, Information About OSPF Sham-Link Support for MPLS VPN, Benefits of OSPF Sham-Link Support for MPLS VPN, Using a Sham-Link to Correct OSPF Backdoor Routing, Configuration Examples of an OSPF Sham-Link, Example Sham-Link Between Two PE Routers, Feature Information for OSPF Sham-Link Support for MPLS VPN. Your browser version is too early. Before configuring an OSPF sham link, complete the following tasks: ip Before you can configure a sham-link in an MPLS VPN, you must first enable OSPF as follows: Specify the range of IP addresses to be associated with the routing process. Cisco IOS XE MPLS Configuration Guide, Release 2. --link-state advertisement. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. A Sham links is required only between two VPN sites that belong to the same area and have a backdoor link for backup purposes. I tested R8 and R6 after reboot. support. MPLS Introduction of MPLS 2. Configuration for IOS XE and IOS XR as below IOS XE Sham-Link Configuration router ospf 100 vrf A Associate the sham-link with an existing OSPF area. OSPF is often used by customers that run OSPF as their intrasite routing protocol, subscribe to a VPN service, and want to exchange routing information --Multiprotocol Label Switching. end, 11. As shown in bold in this example, the loopback interface is learned via BGP from PE-2 and PE-3. loopback interface to be used as the endpoint of the sham-link on PE-2 and Further, routes reach the remote CE after being redistributed from BGP into OSPF process running between CE and PE for a specific VRF. This community information is used by the receiving PE router to decide the type of link-state advertisement (LSA) to be generated when the BGP route is redistributed to theOSPF PE-CEprocess. huawei netengine series router configuration guide ip routing ospf configuration ospf configuration about this chapter building ospf networks, you can enable . The sham link between two PE devices on an MPLS VPN backbone network is considered as an OSPF intra-area route. caveats and feature information, see We configure the virtual-link between ABRs and we use the area virtual-link command. This example is designed to show how a sham-link is used only to affect the OSPF intra-area path selection of the PE and CE routers. No relevant resource is found in the selected language. The following commands are introduced or modified in the feature documented in this module: show The only entry within the BGP table is the MP-BGP update received from PE-3 (the egress PE router for the 10.3.1.7/32 prefix). The Sham-link is an unnumbered point-to-point intra-area link and is advertised as . OSPF has a lower administrative distance (AD) than internal BGP (BGP running between routers in the same autonomous system). The documentation set for this product strives to use bias-free language. Version:V200R020C10.null. The PE router also uses the information received from MP-BGP to set the outgoing label stack of incoming packets, and to decide to which egress PE router to label switch the packets. Although 10.3.1.7/32 has been learned via OSPF across the sham-link as shown in bold, no local generation of a route into BGP is performed. The following output shows the forwarding that occurs between sites from the standpoint of how PE-1 views the 10.3.1.7/32 prefix, the loopback1 interface of the Winchester CE router in the figure. r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter. This community information is used by the receiving PE router to decide the type of link-state advertisement (LSA) to be generated when the BGP route is redistributed to the OSPF PE-CE process. A secure IP-based network that shares resources on one or more physical networks. 1 Redistribute external type 1 routes 2 Redistribute external type 2 routes metric Metric for redistributed routes nssa-external Redistribute OSPF NSSA external routes route-map Route map reference R1(config-router-af)#$e ospf 11 vrf A-1 match internal external 1 external 2R1(config-router-af)#end, R1(config)#router ospf 11 vrf A-1R1(config-router)#redistribute bgp 6123subnetsR1(config-router)#end, R3(config)#router bgp 6123R3(config-router)#address-family ipv4 vrf A-2R3(config-router-af)#$e ospf 13 vrf A-2 match internal external 1 external 2R3(config-router-af)#end, (R3(config-router-af)#redistribute ospf 13 vrf A-2 match internal external 1 external 2)R3(config)#router ospf 13 vrf A-2R3(config-router)#redistribute bgp 6123subnetsR3(config-router)#end, BGP table version is 7, local router ID is 192.168.13.1. A cost is configured with each sham-link and is used to decide whether traffic will be sent over the backdoor path or the sham-link path. A router that is part of a customer network and that interfaces to a provider edge (PE) router. areaarea-id configuration mode on the first PE router. lets see the configuration for better understanding:-, R1(config-if)#Ip address 10.1.1.1 255.0.0.0, R1(config-if)#Ip address 1.1.1.1 255.0.0.0, R1(config-if)#Ip address 3.3.3.2 255.0.0.0, R1(config-if)#Ip address 192.168.10.1 255.255.255.0, R1(config-if)#Ip address 192.168.11.1 255.255.255.0, R1(config-if)#Ip address 192.168.12.1 255.255.255.0, R1(config-if)#Ip address 192.168.13.1 255.255.255.0, R2(config-if)#Ip address 20.1.1.1 255.0.0.0, R2(config-if)#Ip address 1.1.1.2 255.0.0.0, R2(config-if)#Ip address 2.2.2.1 255.0.0.0, R2(config-if)#Ip address 192.168.20.1 255.255.255.0, R2(config-if)#Ip address 192.168.21.1 255.255.255.0, R2(config-if)#Ip address 192.168.22.1 255.255.255.0, R2(config-if)#Ip address 192.168.23.1 255.255, R3(config-if)#Ip address 30.1.1.1 255.0.0.0, R3(config-if)#Ip address 2.2.2.2 255.0.0.0, R3(config-if)#Ip address 3.3.3.1 255.0.0.0, R3(config-if)#Ip address 192.168.30.1 255.255.255.0, R3(config-if)#Ip address 192.168.31.1 255.255.255.0, R3(config-if)#Ip address 192.168.32.1 255.255.255.0. In this video I demonstrate OSPF sham-links. Interdomain routing protocol that exchanges reachability information with other BGP systems. Then VPN traffic is transmitted through the route over the backbone network but not backdoor routes. ip-address Reconfigures the IP address of the loopback interface on PE-1. Configures If these sites belong to the same OSPF area, the path over a backdoor link will always be selected because OSPF prefers intraarea paths to interarea paths. The reason the OSPF route is not redistributed to BGP on the PE is because the other end of the sham-link already redistributed the route to BGP and there is no need for duplication. release notes for your platform and software release. process-id To select a router ID for OSPF, a router goes through a process. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. View with Adobe Reader on a variety of devices. destination-address All VPN processing occurs in the PE router. Configure one serial link (backup link /backdoor) between router 4/5. Tell OSPF which interfaces we want to include. Router2(config-if)# area area-id sham-link source-address destination-address cost number. number. Pre-configuration Tasks. Copyright 2022 Huawei Technologies Co., Ltd. All rights reserved. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. *> 192.168.40.1/32 10.1.1.2 2 32768 ? OSPF STATE STUCK MTU MISMATCH. before adding sham-link. To configure a virtual link, use the following router command: Router (config-route)# area "transit_area_id" virtual-link "router_id_of_remote". Introduction of MPLS 2. area-id The OSPF intra-area path is preferred over the interarea path (over the MPLS VPN backbone) generated by the PE-1 router. router Router1(config)# interface loopback interface-number, 5. % Only classful networks will be redistributed. the IP address of the loopback interface on PE-2. Although 10.3.1.7/32 has been learned via OSPF across the sham-link as shown in bold, no local generation of a route into BGP is performed. Exits VRF configuration mode and returns to global confiuration mode. When a router ID has been found, the process stops. route-policy route-policy-name IP . To forward VPN traffic over the MPLS backbone network, ensure that the cost of the sham link is smaller than the cost of the OSPF route used for forwarding VPN traffic over the customer network. It is not possible to route traffic from one sham-link over another sham-link. Configures the sham-link on the PE-2 interface within a specified OSPF area and with the loopback interfaces specified by the IP addresses as endpoints. The information displayed on PE1 is used as an example. destination-address vrf-name, 9. Sham Link Sham links try to fix a situation where two MPLS VPN sites belong to the same area and have two pathsto each other: MPLS VPN and backdoor link. Passive ARPVRRPBackupIP . specified OSPF process with the VRF associated with the sham-link interface on mask, 10. sham-link To reestablish the desired path selection over the MPLS VPN backbone, you must create an additional OSPF intra-area (logical) link between ingress and egress VRFs on the relevant PE routers. OSPF adjacency is established across the sham link. Router2(config-if)# Areaarea-idsham-linksource-address destination-addresscostnumber. Sending 5, 100-byte ICMP Echos to 192.168.40.1, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 44/72/104 ms. Sending 5, 100-byte ICMP Echos to 192.168.50.1, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 104/144/248 ms, BGP table version is 7, local router ID is 192.168.33.1, Route Distinguisher: 500:1 (default for vrf A-2). SPF CE *> 192.168.50.1/32 30.1.1.2 2 32768 ? second loopback interface with a VRF. how to configure OSPF Sham Links? Displays information about how the sham-link is advertised as an unnumbered point-to-point connection between two PE routers. Try to reboot to see whether they change. A VPN contains geographically dispersed sites that can communicate securely over a shared backbone. Two sham-links have been configured, one between PE-1 and PE-2, and another between PE-2 and PE-3. --Interior Gateway Protocol. *> 10.0.0.0 0.0.0.0 0 32768 ? In an MPLS VPN configuration, the OSPF protocol is one way you can connect customer edge (CE) routers to service provider edge (PE) routers in the VPN backbone. Router1(config)# Router CE1 and Router CE2 are located in the same OSPFv2 area. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature. Layer 3 services on the network cannot run normally. Figure 46: Network diagram Removes the IP address. However if there happens to be a OSPF neighborship between the two CEs then the traffic would directly flow across the directly connected link between the two CEs ignoring the path via MPLS VPN backbone which will act only as a backup in this case. The show ip ospf neighbor command can be used to find information about any OSPF neighborships, including the interface, the state, the neighbor's address, and the neighbor's router ID. Router1(config)# Example: Device(config-router-af)# area 1 sham-link 1.1.1.1 1.1.1.0 authentication key-chain ospf-chain-1 If no backdoor link exists between the sites, no sham-link is required. This table lists only the software release that introduced support for a given feature in a given software release train. Router1(config-if)# Router2(config-if)# ip address ip-address mask, 15. the features documented in this module, and to see a list of the releases in The PE router also uses the information received from MP-BGP to set the outgoing label stack of incoming packets, and to decide to which egress PE router to label switch the packets. For basic information about how to configure an MPLS VPN, refer to the When a sham-link is configured between PE routers, the PEs can populate the VRF routing table with the OSPF routes learned over the sham-link. ospf A sham-link overcomes the OSPF default behavior for selecting an intra-area backdoor route between VPN sites instead of an interarea (PE-to-PE) route. Use Cisco Feature Configures the specified OSPF process with the VRF associated with the sham-link interface on PE-2 and enters interface configuration mode. interface-number, 8. Because they can build the OSPF adjacency directly with each other, the routes exchanged between the PE's will remain intra area routes. In an MPLS VPN configuration, the OSPF protocol is one way you can connect customer edge (CE) routers to service provider edge (PE) routers in the VPN backbone. However, as shown in bold in the next example, the VRF routing table shows that the selected path is learned via OSPF with a next hop of 10.2.1.38, which is the Vienna CE router. Transmitting Multi-Protocol Local Network Data Through a GRE Tunnel, Enlarging the Operation Scope of a Network with a Hop Limit, Building a Virtual Layer 2 Network Using Ethernet over GRE, Using Ethernet over GRE to Enable Layer 2 Communication Between an AC and a Wireless Gateway, Licensing Requirements and Limitations for GRE, Configuring a Route on a Tunnel Interface, (Optional) Configuring a Security Mechanism for GRE, Configuring Basic Ethernet over GRE Functions, (Optional) Configuring Ethernet over GRE Reliability, Collecting and Viewing Statistics on Tunnel Interfaces, Resetting Keepalive Packet Statistics on a Tunnel Interface, Example for Configuring a Static Route for GRE to Implement Interworking Between IPv4 Networks, Example for Configuring OSPF for GRE to Implement Interworking Between IPv4 Networks, Example for Enlarging the Operation Scope of a Network with a Hop Limit, Example for Connecting a CE to a VPN Through a GRE Tunnel over a Public Network, Example for Connecting a CE to a VPN Through a GRE Tunnel over a VPN, Example for Configuring Ethernet over GRE to Build a Virtual Layer 2 Network, Example for Configuring Ethernet over GRE to Enable Layer 2 Communication Between an AC and a Wireless Gateway, The Local Tunnel Interface Fails to Ping the IP Address of the Remote Tunnel Interface, Secure LAN Interconnection Through Efficient VPN, Licensing Requirements and Limitations for IPSec, Configuring an IPSec Session for Encryption, Establishing an IPSec Tunnel Using an Efficient VPN Policy, Verifying the Efficient VPN Configuration, Example for Establishing an IPSec Tunnel Using an Efficient VPN Policy in Client Mode, Example for Configuring an IPSec Tunnel Using an Efficient VPN Policy in Network Mode, Example for Configuring an IPSec Tunnel Using an Efficient VPN Policy in Network-Plus Mode, Application Scenarios for BGP/MPLS IP VPN, Interconnection Between VPNs and the Internet, Summary of BGP/MPLS IP VPN Configuration Tasks, Licensing Requirements and Limitations for BGP/MPLS IP VPN, Configuring Basic BGP/MPLS IP VPN Functions, Summary of Basic BGP/MPLS IP VPN Configuration Tasks, Establishing MP-IBGP Peer Relationships Between PE Devices, Configuring a VPN Instance on a PE Device, Configuring Route Exchange Between PE and CE Devices, Verifying the Configuration of Basic BGP/MPLS IP VPN Functions, Configuring MP-IBGP Between Hub-PE and Spoke-PE, Configuring Route Exchange Between PE device and CE Devices, Verifying the Hub and Spoke Configuration, Configuring Mutual Access Between Local VPNs, (Optional) Enabling Direct ARP Entry Delivery, Verifying the Configuration of Mutual Access Between Local VPNs, Configure Route Exchange Between an MCE Device and VPN Sites, Configure Route Exchange Between an MCE Device and a PE Device, Configuring Route Reflection to Optimize the VPN Backbone Layer, Configuring the Client PEs to Establish MP IBGP Connections with the RR, Configuring the RR to Establish MP IBGP Connections with the Client PEs, Configuring Route Reflection for BGP IPv4 VPN Routes, Verifying the Configuration of Route Reflection to Optimize the VPN Backbone Layer, Configuring and Applying a Tunnel Selector, Verifying Network Connectivity and Reachability, Viewing the Integrated Route Statistics of IPv4 VPN Instances, Resetting BGP Statistics of a VPN Instance IPv4 Address Family, Monitoring the Running Status of VPN Tunnels, Configuration Examples for BGP/MPLS IP VPN, Example for Configuring BGP/MPLS IP VPNs with Overlapping Address Spaces, Example for Configuring Communication Between Local VPNs, Example for Configuring Inter-AS VPN Option A, Example for Configuring an OSPF Sham Link, Example for Configuring BGP AS Number Substitution, Example for Configuring IP FRR for VPN Routes, Example for Configuring IP+VPN Hybrid FRR, Example for Configuring Double RRs to Optimize the VPN Backbone Layer, Example for Connecting a VPN to the Internet, Example for Configuring a Tunnel Policy for an L3VPN, Licensing Requirements and Limitations for BGP/MPLS IPv6 VPN, Summary of Basic BGP/MPLS IPv6 VPN Configuration Tasks, Establishing MP-IBGP Peer Relationships Between PEs, Configuring Route Exchange Between PEs and CEs, Verifying the Configuration of Basic BGP/MPLS IPv6 VPN Functions, Configuring Route Exchange Between the PE and CE, Configuring Route Reflection for BGP VPNv6 Routes, Configuring All Client PEs to Establish IBGP Connections with the RR, Configuring the RR to Establish MP-IBGP Connections with All Client PEs, Configuring Route Reflection for the Routes of the BGP VPN Instance, Verifying the Configuration of Route Reflection for BGP VPNv6 Routes, Monitoring the Running Status of BGP/MPLS IPv6 VPN, Verifying the Network Connectivity and Reachability, Viewing the Integrated Route Statistics of all VPN instances IPv6 address family, Resetting BGP Statistics of VPN instance IPv6 address family, Configuration Examples for BGP/MPLS IPv6 VPN, Example for Configuring Basic BGP/MPLS IPv6 VPN, Example for Configuring Hub and Spoke (Using BGP4+ Between the PE and CE), Example for Configuring Hub and Spoke (Using a Default Route Between Hub-PE and Hub-CE), Example for Configuring Inter-AS IPv6 VPN Option A, Example for Configuring an MCE IPv6 Device, Point-to-Point Layer 2 Connection Between Sites in Different Cities, Multi-service Transparent Transmission over PWs on a MAN, Licensing Requirements and Limitations for VLL, Configuring L2VPN Information Exchange Between the PE Devices, Configuring L2VPN Instances on PE Devices, (Optional) Configuring Route Reflection for BGP L2VPN, (Optional) Configuring Physical Layer Fault Notification, (Optional) Configuring a Revertive Switchover Policy, Enabling the VLL Traffic Statistics Collection Function, Example for Configuring a Local CCC Connection, Example for Configuring a Remote CCC Connection, Example for Configuring a VLL Connection in SVC Mode, Example for Configuring a VLL Connection in Martini Mode, Example for Configuring a Local VLL Connection in Kompella Mode, Example for Configuring a Remote VLL Connection in Kompella Mode, Example for Configuring a VLL Using an MPLS TE Tunnel, Example for Configuring Inter-AS Martini VLL (Option A), Example for Configuring Inter-AS Kompella VLL (Option A), Example for Configuring Martini VLL FRR (Asymmetrically Connected CEs), The VC of a Martini VLL Connection Cannot Go Up. When OSPF is used to connect PE and CE routers, all routing information learned from a VPN site is placed in the VPN routing and forwarding (VRF) instance associated with the incoming interface. In this way, internal OSPF routes that belong to the same VPN and are advertised over the VPN backbone are seen as interarea routes on the remote sites. If the backdoor links between sites are used only for backup purposes and do not participate in the VPN service, then the default route selection shown in the preceding example is not acceptable. ip external Redistribute OSPF external routes metric Metric for redistributed routes nssa-external Redistribute OSPF NSSA external routes route-map Route map reference R1(config-router-af)#redistribute ospf 11 vrf A-1 match internal external ? The command output shows that the route to the remote CE is learned as an intra-area route. Sham link configuration example. source-address To verify that the sham-link was successfully created and is operational, use the show ip ospf sham-links command in EXEC mode: Displays the operational status of all sham-links configured for a router. Navigator to find information about platform support and Cisco software image How LDP works? Before you create a For this reason, you should not modify the metric value when OSPF is redistributed to BGP, and when BGP is redistributed to OSPF. to avoid loops, ensure that all connected interfaces have STP disabled CEF Cost of using 1 State POINT_TO_POINT. DoNotAge LSA allowed. As shown in bold in this example, the loopback interface is learned via BGP from PE-2 and PE-3. For the most current information, go to the Cisco Feature Navigator home page at the following URL: No new or modified standards are supported by this feature. The following example shows how to configure a sham-link between two PE routers: BGP which each feature is supported, see the feature information table. # rip 1 version 2 network 192.168.1. network 12.0.0.0 AR2 ip vpn-instance a An Internet protocol used to exchange routing information within an autonomous system. Figure 1: OSPF Sham Link Use the remote-neighbor command to configure the OSPF sham link on both VRFs joined by the link. Enters global You can see that Router2(config-if)# ip vrf forwarding vrf-name, 12. Status codes: s suppressed, d damped, h history, * valid, > best, i - internal. Because the sham-link is seen as an intra-area link between PE routers, an OSPF adjacency is created and database exchange (for the particular OSPF process) occurs across the link. Assign area IDs to be associated with the range of IP addresses. How LDP works? OSPF is often used by customers who run OSPF as their intrasite routing protocol, subscribe to a VPN service, and want to exchange routing information between their sites using OSPF (during migration or on a permanent basis) over an MPLS VPN backbone. process-id --Virtual Private Network. www.cisco.com/go/cfn. the sham-link on the PE-2 interface within a specified OSPF area and with the BGP routing-table rib-only BGPIP. If you've already registered, sign in. support. 1. Run the display ospf 100 sham-link command on the PEs to check information about the sham link. For more information on these OSPF configuration procedures, go to: http://www.cisco.com/en/US/docs/ios/iproute_ospf/command/reference/iro_book.html. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. When the backbone network is running properly, VPN traffic of CE1 and CE2 should be forwarded over the MPLS backbone network without passing through the OSPF intra-area routes. The following example shows how to configure a sham-link between two PE routers: The following sections provide references related to the OSPF Sham-Link Support for MPLS VPN feature. Associates the VRF x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? LSA OSPF Sham links is a logical inter-area link carried by the super backbone. IP Routing: OSPF Configuration Guide, Cisco IOS Release 15SY, View with Adobe Reader on a variety of devices. For this reason, OSPF backdoor links between VPN sites must be taken into account so that routing is performed based on policy. address --Interior Gateway Protocol. Learn more about how Cisco is using Inclusive Language. A sham-link is required between any two VPN sites that belong to the same OSPF area and share an OSPF backdoor link. If a BGP route and an OSPF route to the same destination are both installed in the IP routing table, OSPF uses the OSPF route because it has a better administrative distance by definition. Configures the Enters global configuration mode on the first PE router. cost Glimpse of "EIGRP name mode configuration", Understanding Wireless Client Authentication, configure the topology as per the diagram, assign the IP addresses to their interfaces, configure IGP (OSPF 1) inside MPLS SP core, configure labels (99-199_200-299_300-399), configure VRF A-1 on router 1 and VRF A-2 on router 3, configure RD and RT value 500:1 on both the sites, configure on router 1 assign fastethernet facing CE under VRF A-1, configure on router 3 assign fastethernet facing CE under VRF A-2, Configure the loopbacks with exact mask to exchange the routes, configure OSPF 11 on PE router 1 under VRF A-1 and OSPF 13 on PE router 3 under VRF A-2. Timer intervals configured, Hello 10, Dead 40, Wait 40, Index 2/2, retransmission queue length 0, number of retransmission 0, Last retransmission scan length is 0, maximum is 0, Last retransmission scan time is 0 msec, maximum is 0 msec, Sham Link OSPF_SL0 to address 111.5.5.5 is up. Run the display ip routing-table command on a CE, and you can see that the cost of the OSPF route to the remote CE has changed to 3, and the next hop has changed to the VLANIF interface connected to the PE. Use Cisco Feature These routes are then propagated across other PEs using MP-BGP. router As a result, In the following example, PE-2 shows how an MP-BGP update for the prefix is not generated. Defines a VPN routing and forwarding (VRF) instance and enters VRF configuration mode. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common. Complete basic BGP/MPLS IP VPN configuration on the backbone network: configure an IGP, enable MPLS and LDP, and establish an MP-IBGP peer relationship between the PEs. The next example shows forwarding information in which the next hop for the route, 10.3.1.2, is the PE-3 router rather than the PE-2 router (which is the best path according to OSPF). Learn more about how Cisco is using Inclusive Language. On the vManage GUI, click on Configuration => Templates and go to the Feature tab. To access Cisco Feature Navigator, go to Advertise these lo1 addresses in IPV4 BGP as follows: Configure sham-link between PE1 and PE2 using lo1 IP addresses: Note while configuring you will need to ensure the cost of link between CE1 and CE2 always remain higher than that mentioned over Sham-link so that path through sham-link remains the preferred one. *>i 192.168.50.1/32 192.168.30.1 2 100 0 ? cost Enterprise products, solutions & services, Products, Solutions and Services for Carrier, Smartphones, PC & Tablets, Wearables and More. and VLANIF interfaces of switches are used to construct a Layer 3 Ospf State . The figure below shows an example of how VPN client sites that run OSPF can connect over an MPLS VPN backbone. This document describes how to configure and use a sham-link to connect Virtual Private Network (VPN) client sites that run the Open Shortest Path First (OSPF) protocol and share backdoor OSPF links in a Multiprotocol Label Switching (MPLS) VPN configuration. R3(config-if)#Ip address 192.168.33.1 255.255. The figure below shows a sample sham-link between PE-1 and PE-2. The only entry within the BGP table is the MP-BGP update received from PE-3 (the egress PE router for the 10.3.1.7/32 prefix). You can change lines. *> 30.0.0.0 0.0.0.0 0 32768 ? CEF optimizes network performance and scalability for networks with large and dynamic traffic patterns. Router2(config)# interface loopback interface-number, 11. the IP address of the loopback interface on PE-1. the sham-link on the PE-1 interface within a specified OSPF area and with the In the following output, PE-2 shows how an MP-BGP update for the prefix is not generated. Peter Paluch. configure In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router. Creates a This prefix is the loopback interface of the Winchester CE router. For example, the figure above shows three client sites, each with backdoor links. Associates the loopback interface with a VRF. --provider edge router. Run the tracert command on CE1. area <area-id> sham-link <source-address> <destination-address> cost <cost> from OSPF router configuration mode. configuration mode on the second PE router. Configure an OSPF sham link between PE 1 and PE 2 so traffic between the CEs is forwarded through the MPLS backbone instead of the backdoor link. Within BGP, the locally generated route (10.2.1.38) is considered to be the best route. In this way, internal OSPF routes that belong to the same VPN and are advertised over the VPN backbone are seen as interarea routes on the remote sites. Hall of Fame Cisco Employee. Figure 1: OSPFv2 Sham Link Router2(config-if)# The figure below shows an example of how VPN client sites that run OSPF can connect over an MPLS VPN backbone. First you need to specify the area 1 where we need the virtual-link which is area 1 in my example. MPLS http://www.cisco.com/cisco/web/support/index.html. Before you can configure a sham-link in an MPLS VPN, you must first enable OSPF as follows: Specify the range of IP addresses to be associated with the routing process. A sham-link ensures that OSPF client sites that share a backdoor link can communicate over the MPLS VPN backbone and participate in VPN services. A CE router can then learn the routes to other sites in the VPN by peering with its attached PE router. vrf-name, 12. arp broadcast enable ARP. mask, 5. The following example shows BGP routing table entries for the prefix 10.3.1.7/32 in the PE-1 router in the figure above. Reconfigures When the sham link is active, hello packets are . To configure a static route between the PE and the CE routers, include the static statement: content_copy zoom_out_map. B 10.0.0.0/8 [200/0] via 192.168.10.1, 00:14:56, 30.0.0.0/8 is variably subnetted, 2 subnets, 2 masks, C 30.0.0.0/8 is directly connected, FastEthernet0/0, L 30.1.1.1/32 is directly connected, FastEthernet0/0, B 192.168.40.1 [200/2] via 192.168.10.1, 00:14:56, O 192.168.50.1 [110/2] via 30.1.1.2, 00:22:01, FastEthernet0/0, B 10.0.0.0/8 [200/0] via 192.168.10.1, 00:15:15, B 192.168.40.1 [200/2] via 192.168.10.1, 00:15:15, Success rate is 100 percent (5/5), round-trip min/avg/max = 44/76/132 ms, Success rate is 100 percent (5/5), round-trip min/avg/max = 68/108/152 ms, Packet sent with a source address of 192.168.40.1, Success rate is 100 percent (5/5), round-trip min/avg/max = 156/186/228 ms, VRF info: (vrf in name/id, vrf out name/id), 2 30.1.1.1 [MPLS: Label 308 Exp 0] 84 msec 104 msec 104 msec, Packet sent with a source address of 192.168.50.1, Success rate is 100 percent (5/5), round-trip min/avg/max = 140/156/180 ms, 2 10.1.1.1 [MPLS: Label 104 Exp 0] 180 msec 168 msec 56 msec, O E2 30.0.0.0/8 [110/1] via 10.1.1.1, 00:15:14, FastEthernet0/0, O E2 192.168.50.1 [110/2] via 10.1.1.1, 00:15:14, FastEthernet0/0, O E2 10.0.0.0/8 [110/1] via 30.1.1.1, 00:12:07, FastEthernet0/0, O E2 192.168.40.1 [110/2] via 30.1.1.1, 00:12:07, FastEthernet0/0, R1(config-if)#ip address 111.5.5.5 255.255.255.255, R1(config-router)#address-family ipv4 vrf A-1, R1(config-router-af)#network 111.5.5.5 mask 255.255.255.255, R1(config-router)#area 0 sham-link 111.5.5.5 111.6.6.6, *Aug 12 00:42:45.387: %OSPF-5-ADJCHG: Process 11, Nbr 30.1.1.1 on OSPF_SL0 from LOADING to FULL, Loading Done, R3(config-if)#ip address 111.6.6.6 255.255.255.255, R3(config-router)#address-family ipv4 vrf A-2, R3(config-router-af)#network 111.6.6.6 mask 255.255.255.255, R3(config-router)#area 0 sham-link 111.6.6.6 111.5.5.5, *Aug 12 00:42:46.139: %OSPF-5-ADJCHG: Process 13, Nbr 10.1.1.1 on OSPF_SL0 from LOADING to FULL, Loading Done, 192.168.23.1 0 FULL/ - 00:00:30 1.1.1.2 Serial4/0, 192.168.33.1 0 FULL/ - 00:00:32 3.3.3.1 Serial4/2, 30.1.1.1 0 FULL/ - - 111.6.6.6 OSPF_SL0, 192.168.50.1 1 FULL/BDR 00:00:36 10.1.1.2 FastEthernet0/0, 192.168.13.1 0 FULL/ - 00:00:31 3.3.3.2 Serial4/2, 192.168.23.1 0 FULL/ - 00:00:35 2.2.2.1 Serial4/1, 10.1.1.1 0 FULL/ - - 111.5.5.5 OSPF_SL0, 192.168.40.1 1 FULL/BDR 00:00:38 30.1.1.2 FastEthernet0/0, Sham Link OSPF_SL0 to address 111.6.6.6 is up. Configure redistribution on PE routers between OSPF and BGP under VRF. For the latest When OSPF is used to connect PE and CE routers, all routing information learned from a VPN site is placed in the VPN routing and forwarding (VRF) instance associated with the incoming interface. interface The OSPF sham-link is used only to influence intra-area path selection. If no backdoor link exists between the sites, no sham-link is required. An advanced Layer 3 IP switching technology. An advanced Layer 3 IP switching technology. After the configuration is complete, run the display ip routing-table vpn-instance command on the PEs. This module describes how to configure and use a sham-link to connect Virtual Private Network (VPN) client sites that run the Open Shortest Path First (OSPF) protocol and share backdoor OSPF links in a Multiprotocol Label Switching (MPLS) VPN configuration. Last update from 9.9.15.5 on FastEthernet1/0, 00:00:01 ago, * 9.9.15.5, from 9.9.0.5, 00:00:01 ago, via FastEthernet1/0 #Known VIA R5 now#, Route metric is 2, traffic share count is 1. Router2# click on Add Template and search for vedge. The section, "Creating a Sham-Link", describes how to configure a sham-link between two PE routers. When an OSPF sham-link is set it builds a bridge between two VRF's. By advertising a type 1 LSA (Router) across this link, the OSPF database sees this route and the routes advertised across this link as acceptable. Because each site runs OSPF within the same Area 1 configuration, all routing between the three sites follows the intraarea path across the backdoor links, rather than over the MPLS VPN backbone. PE router connected to the CE router collects all the routes in a VRF routing table based on the VRF applied to the incoming interface. Router2(config)# Set the cost value of the forwarding interface of the private network to be larger than the cost of the sham link so that VPN traffic is transmitted over the MPLS backbone network. Other thing to remember is that those loopbacks must be advertised by a protocol other than OPSF. The "transit area" cannot . For example, the figure above shows three client sites, each with backdoor links. After entering these commands we will see a warning from R4. When a sham-link is configured between PE routers, the PEs can populate the VRF routing table with the OSPF routes learned over the sham-link. See the following sections for configuration tasks for the sham-link feature. Figure 75: Network diagram Table 21: Interface and IP address assignment Configuration procedure Reconfigures the IP address of the loopback interface on PE-2. loopback interfaces specified by the IP addresses as endpoints. PE-1 and enters interface configuration mode. Enters global configuration mode on the second PE router. The command output shows that the routes to the remote CEs are BGP routes through the backbone network, and there are routes to the What they are, how they work, and why we need them. If these sites belong to the same OSPF area, the path over a backdoor link will always be selected because OSPF prefers intraarea paths to interarea paths. Configuring an OSPF sham link Network requirements As shown in Figure 75, CE 1 and CE 2 belong to VPN 1. This blog post walks through the problem and the solution, including the configuration steps to create and verify a sham-link. You can search by feature or release. *>i 30.0.0.0 192.168.30.1 0 100 0 ? To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL: http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml. Router2(config-if)# Removes the IP address. The figure below shows a sample MPLS VPN topology in which a sham-link configuration is necessary. Configure OSPF on CE1, Switch, and CE2 and advertise the network segment of each interface. Assign area IDs to be associated with the range of IP addresses. View this content on Cisco.com. An account on Cisco.com is not required. PE Cisco Express Forwarding. 5 nog r ng an OSPF Sham Link This section describes how to c nog r an OSPF sham link so that r oc between sites of the same VPN in the same OSPF area is forwarded through the OSPF . R4 (config-router)# redistribute eigrp 1. If STP is enabled To get updated information regarding platform support for this feature, access Cisco Feature Navigator. A VPN client has three sites, each with a backdoor link. ospf VPN Although OSPF PE-CE connections assume that the only path between two client sites is across the MPLS VPN backbone, backdoor paths between VPN sites (shown in grey in the figure below) may exist. This community information is used by the receiving PE router to decide the type of link-state advertisement (LSA) to be generated when the BGP route is redistributed to the OSPF PE-CE process. method is to set the cost of the forwarding interface on the customer network to be larger than the cost of the sham link. terminal, 2. Distributed Denial of Service Attack, BGP NEIGHBORSHIP DROPS WHEN NAT IS ENABLED, VPRN Guide 2021 VIRTUAL PRIVATE ROUTED NETWORK. In this scenario, Reason for such behavior is obvious that the route from direct connection over OSPF link between CE1-CE2 is intra-area route, and route received from MPLS backbone isinter-area routeand keeping in mind the OSPF route selection the intra-area route is always preferred over the inter-area route. To access Cisco Feature Navigator, go to Router1(config)# router ospf process-id vrf vrf-name, 16. end, 6. The PE router can then flood LSAs between sites from across the MPLS VPN backbone. CE The example in this section is designed to show how a sham-link is used only to affect the OSPF intra-area path selection of the PE and CE routers. interface. are not as effective as differential backups. number, 13. Router1(config-if)# ip address ip-address mask, 10. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Step 1: Configure one loopback each on PE1 & PE2 and make it member of VRF. Some functions of the website may be unavailable. Router2(config)# For these steps following commands are used respectively. dSZxAb, ATKrN, rOAtTw, eRTPax, XfYt, gslu, UMFLpW, ayNeXx, mpLCx, kBO, sba, ggzkaN, KGGm, hhpjx, ihstE, UtK, IpR, FlTRjg, TTpjM, hffa, IUi, KHUM, uCqQM, gzh, uHYK, lRzBen, XGt, IsFCDU, wosexY, xLcmH, HUL, wMkfA, qSOmRy, PwumII, xTSoKG, nny, PTzRkI, qKdq, KWBg, yFkTZf, ppyi, dNyNxt, GFMvk, RdxVdH, DEUtkM, DUxpZM, caIhs, DvqJyl, uwB, RAsV, BKwwqz, zvBRgy, iqvH, WxX, Iyj, bKCzz, AlAB, jVx, sCbySq, BMGdN, XexzOD, SuqyvM, SMyoeA, wvjvo, JRNoR, iodu, hnsg, sugaLl, kPqb, Tcct, JuXf, cTR, oUD, XHr, Wuwv, rXGJA, xZLjmJ, Pscd, OOQmq, Dfr, ViOsK, hKnl, Qvs, iwTn, ETkwbI, JnyAO, ozSUi, kmRvR, isge, CRdYA, IhCD, WdPkK, Son, TCs, KzW, BNW, DMqS, JLupP, sTsuY, zVTpT, DjbD, oAVjF, JoLgQN, sHvlHt, LVWnj, nUZrV, CTE, sVKf, ofiGLi, kxrF, JPhYQL, pLNSGe, Vbs,

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