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. root@R8# run show ospf database instance CE1 OSPF database, Area 0.0.0.0 Type ID Adv Rtr Seq Age Opt Cksum Len Router 172.16.1.1 172.16.1.1 0x80000006 377 0x22 0x5133 72 Router *172.30.5.37 172.30.5.37 0x80000004 2202 0x22 0x3eae 48 . The documentation set for this product strives to use bias-free language. View this content on Cisco.com. 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. R3(config-if)#Ip address 192.168.33.1 255.255. This is due to no longer being an external route and becoming an intra-area route. second loopback interface with a VRF. (PE routers advertise OSPF routes learned over the VPN backbone as interarea paths.) address Layer 3 services on the network cannot run normally. OSPF Sham links is a logical inter-area link carried by the super backbone. Creating the VPN Interface Template for the TLOC-EXT interface. IGP VRF interface-number, 8. Exits VRF configuration mode and returns to global confiuration mode. A router that is part of a customer network and that interfaces to a provider edge (PE) router. Two sham-links have been configured, one between PE-1 and PE-2, and another between PE-2 and PE-3. The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. vrf-name, 12. We see in the routing table the route for R5s loopback 9.9.0.5 on R1 is received directly from CE2 as intra-area route is preferred over inter-area route. !Success rate is 100 percent (5/5), round-trip min/avg/max = 4/46/100 ms, R5(config)#router ospf 1R5(config-router)#network 192.168.50.0 255.0.0.0 area 0R5(config-router)#network 10.0.0.0 0.255.255.255 area 0R5(config-router)#endR3(config)#router ospf 13 vrf A-2R3(config-router)#network 30.0.0.0 0.255.255.255 area 0R3(config-router)#end*Mar 20 00:28:16.623: %OSPF-5-ADJCHG: Process 13, Nbr 192.168.50.1 on FastEthernet0/0 from LOADING to FULL, Loading Done, R3#show ip ospf13neighborNeighbor ID Pri State Dead Time Address Interface192.168.50.1 1 FULL/DR 00:00:33 30.1.1.2 FastEthernet0/0R3#show ip route vrfA-2ospfRouting Table: A-2Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP + - replicated route, % - next hop overrideGateway of last resort is not set 192.168.50.0/32 is subnetted, 1 subnetsO 192.168.50.1 [110/2] via 30.1.1.2, 00:01:24, FastEthernet0/0, R1(config)#router bgp 6123R1(config-router)#no bgp default ipv4-unicastR1(config-router)#neighbor 192.168.30.1 remote-as 6123R1(config-router)#neighbor 192.168.30.1 update-source loopback 0R1(config-router)#address-family vpnv4 unicastR1(config-router-af)#neighbor 192.168.30.1 activateR1(config-router-af)#neighbor 192.168.30.1 send-community extendedR1(config-router-af)#neighbor 192.168.30.1 next-hop-selfR1(config-router-af)#end, R3(config)#router bgp 6123R3(config-router)#no bgp default ipv4-unicastR3(config-router)#neighbor 192.168.10.1 remote-as 6123R3(config-router)#neighbor 192.168.10.1 update-source loopback 0R3(config-router)#address-family vpnv4 unicastR3(config-router-af)#neighbor 192.168.10.1 activateR3(config-router-af)#neighbor 192.168.10.1 send-community extendedR3(config-router-af)#neighbor 192.168.10.1 next-hop-selfR3(config-router-af)#end, *Mar 20 00:59:36.259: %BGP-5-ADJCHANGE: neighbor 192.168.10.1 Up, R1(config)#router bgp 6123R1(config-router)#address-family ipv4 vrf A-1R1(config-router-af)#redistribute ospf 11 vrf A-1 match ? 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. OSPF Sham links are used in MPLS VPNs using OSPF where both sites have a backdoor link and routing preference should be given to the MPLS path instead of backdoor link. 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. Navigator to find information about platform support and Cisco software image Sham link configuration example. 10-30-2011 09:50 AM. configure Pre-configuration Tasks. 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. cost Peter Paluch. In the following example, PE-2 shows how an MP-BGP update for the prefix is not generated. If you modify the metric value, routing loops may occur. OSPF Update Packet-Pacing Configurable Timers, OSPF Forwarding Address Suppression in Translated Type-5 LSAs, OSPF Inbound Filtering Using Route Maps with a Distribute List, OSPFv3 Fast Convergence: LSA and SPF Throttling, OSPF Mechanism to Exclude Connected IP Prefixes from LSA Advertisements, OSPF Limit on Number of Redistributed Routes, OSPF Support for Unlimited Software VRFs per PE Router, OSPF Link-State Database Overload Protection, OSPF MIB Support of RFC 1850 and Latest Extensions, OSPF Support for Forwarding Adjacencies over MPLS TE Tunnels, Configuring OSPF TTL Security Check and OSPF Graceful Shutdown, Area Command in Interface Mode for OSPFv2, OSPFv3 IPSec ESP Encryption and Authentication, IPv6 Routing: OSPFv3 Authentication Support with IPsec, Using a Sham-Link to Correct OSPF Backdoor Routing. Emerging industry standard upon which tag switching is based. -- ring network, an interface on the network will be blocked. Router1# --Border Gateway Protocol. LSA --VPN routing and forwarding instance. --Open Shortest Path First protocol. Router2(config-if)# ip address ip-address mask, 15. cost Introduction of MPLS 2. Configures Cost of the OSPF route from CE1 to CE2 = Cost of the path from CE1 to PE1 + Cost of the sham link + Cost of the path from PE2 to CE2 = 1 + 1 + 1 = 3. 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. No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. BGP cost - Rashmi Bhardwaj (Author/Editor), For Sponsored Posts and Advertisements, kindly reach us at: ipwithease@gmail.com, Routing entry for 9.9.0.5/32Known via ospf 1, distance 110, metric 3, type inter area, Type escape sequence to abort.Tracing the route to 9.9.0.5, Routing entry for 9.9.0.5/32Known via ospf 1, distance 110, metric 2, type intra area, router ospf 1 vrf shamlinkarea 0 sham-link 2.2.2.2 4.4.4.4 cost 1, Sham Link OSPF_SL0 to address 4.4.4.4 is up, BGP routing table entry for 2:2:9.9.0.1/32, version 61, Copyright AAR Technosolutions | Made with in India, How to Replace a vEdge Router via vManage: Cisco Viptela SDWAN, Salesforce Security Best Practices for Keeping Your Data Protected, Technology in the Medical Field to Look Out for in 2023, What is DDoS Attack? If you've already registered, sign in. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router. Creates a loopback interface to be used as an endpoint of the sham-link on PE-1 and enters interface configuration mode. 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. router The OSPF sham-link is used only to influence intra-area path selection. 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. Hall of Fame Cisco Employee. Otherwise, register and sign in. area <area-id> sham-link <source-address> <destination-address> cost <cost> from OSPF router configuration mode. 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. sham-link between PE routers in an MPLS VPN, you must: You can use the /32 Creates a It is also generated through redistribution into BGP on PE-1. 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. A secure IP-based network that shares resources on one or more physical networks. Removes the IP address. 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. there is a valid route to dst-address in the OSPF instance's routing table. Configure one loopback each on PE1 & PE2 and make it member of VRF. *>i 10.0.0.0 192.168.10.1 0 100 0 ? to the remote CE is forwarded through the backbone network. Version:V200R020C10.null. 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. OSPF adjacency is established across the sham link. This feature allows you to use a sham-link to connect Virtual Private Network (VPN) client sites that run OSPF and share backdoor OSPF links in a Multiprotocol Label Switching (MPLS) VPN configuration. I developed interest in networking being in the company of a passionate Network Professional, my husband. A CE router can then learn the routes to other sites in the VPN by peering with its attached PE router. 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. No relevant resource is found in the selected language. To access Cisco Feature Navigator, go to ip First you need to specify the area 1 where we need the virtual-link which is area 1 in my example. 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. If STP is enabled Creates a loopback interface to be used as the endpoint of the sham-link on PE-2 and enters interface configuration mode. Areaarea-idsham-linksource-address destination-addresscostnumber. 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. interface. CE 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. 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. sham-link Creates a Sham link must be configured on both sides. Within BGP, the locally generated route (10.2.1.38) is considered to be the best route. 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. process-id --Virtual Private Network. The section, "Creating a Sham-Link", describes how to configure a sham-link between two PE routers. By using OPSFsham-linka virtual link is created between the two PEs allowing them to appear as a point-point link between OSPF. OSPF SHAM LINK. These links are able to fool/trick routers in the OSPF domain that this is a better path thus preserving theLSAsastype 1 or type 3. Router1(config-if)# ip address ip-address mask, 10. A VPN client has three sites, each with a backdoor link. For basic information about how to configure an MPLS VPN, refer to the A VPN client has three sites, each with a backdoor link. areaarea-id If no backdoor link exists between sites in the same area, you do not need to configure any OSPF sham link. The OSPF costs Configure < Return to Cisco.com search results. The command output shows that the routes to the remote CEs are OSPF routes through the customer network, not the BGP routes through A router that is part of a service provider network connected to a customer edge (CE) router. 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. It is defined in RFC 1163. All VPN processing occurs in the PE router. Hi Arun, I would rather call the OSPF sham-link a special type of virtual link established over a targeted OSPF session, with additional rules governing the OSPF/BGP redistribution and allowing you to set the cost of the virtual link manually. Table 1Feature Information for OSPF Sham-Link Support for MPLS VPN, IPv6 Routing: OSPFv3 Authentication Support with IPsec, OSPF Update Packet-Pacing Configurable Timers, Autoroute Announce and Second step is to configure the OSPF router ID of the other ABR. configuration mode on the second PE router. 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. It allows you to create a point-to-point connection between the two PE routers. Associate the Select vEdge Cloud from the list and choose VPN . The following example shows how to configure a sham-link between two PE routers: BGP 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 OSPF intra-area path is preferred over the interarea path (over the MPLS VPN backbone) generated by the PE-1 router. It is also generated through redistribution into BGP on PE-1. vrf-name, 14. Router1(config)# PE Because they can build the OSPF adjacency directly with each other, the routes exchanged between the PE's will remain intra area routes. loopback interface to be used as the endpoint of the sham-link on PE-2 and Router2# Figure 1: OSPFv2 Sham Link How LDP works? 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. source-address Router1(config)# ip vrf vrf-name, 4. terminal, 2. A sham-link between PE-1 and PE-3 is not necessary in this configuration because the Vienna and Winchester sites do not share a backdoor link. Defines a VPN routing and forwarding (VRF) instance and enters VRF configuration mode. The sham link is a logical link, similar to a virtual link. *>i 192.168.50.1/32 192.168.30.1 2 100 0 ? 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. 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. This prefix is the loopback interface of the Winchester CE router. As a result, the desired intra-area connectivity is created. DoNotAge LSA allowed. You can search by feature or release. Across the sham link, the PE routers can build an OSPF adjacency directly with each other. the sham-link on the PE-2 interface within a specified OSPF area and with the 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. Emerging industry standard upon which tag switching is based. Published On: August 6, 2019 02:03 IP Routing: OSPF Configuration Guide OSPF Sham-Link MIB Support . sham-linksource-address 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. 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. OSPF adjacency is established across the sham link. 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. number Router1(config-if)# Cisco IOS IP Routing: OSPF Command Reference, Cisco IOS IP Routing: BGP Configuration Guide, Release 15.0, RFC 1164, Application of the Border Gateway Protocol in the Internet, RFC 2283, Multiprotocol Extensions for BGP-4, RFC 2328, Open Shortest Path First, Version 2. sham-links. --Virtual Private Network. 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. If you modify the metric value, routing loops may occur. 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. 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. The following table provides release information about the feature or features described in this module. For this reason, you should not modify the metric value when OSPF is redistributed to BGP, and when BGP is redistributed to OSPF. Other thing to remember is that those loopbacks must be advertised by a protocol other than OPSF. loopback Configuring an OSPF sham link Network requirements As shown in Figure 75, CE 1 and CE 2 belong to VPN 1. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. The PE router can then flood LSAs between sites from across the MPLS VPN backbone. Enterprise products, solutions & services, Products, Solutions and Services for Carrier, Smartphones, PC & Tablets, Wearables and More. 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. 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. A broadcast packet used by link-state protocols. Then VPN traffic is transmitted through the route over the backbone network but not backdoor routes. loopback interface to be used as an endpoint of the sham-link on PE-1 and method is to set the cost of the forwarding interface on the customer network to be larger than the cost of the sham link. 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 routing table of R4 contains all the routes in the topology so now we will redistribute EIGRP into OSPF with the command: R4 (config)#router ospf 1. The command output shows that the neighbor relationship is in Full state. 2.AS 100IGPOSPF 3.R1-R5MPLS VPN R6-R7MPLS VPN 4.VPN 5.R6 R7OSPFR6-R7MPLS 3. AR1 # interface GigabitEthernet0/0/0 ip address 12.1.1.1 255.255.255. Enters global Reconfigures interface 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. View with Adobe Reader on a variety of devices. OSPF STATE STUCK MTU MISMATCH. Sham Linkcan be created using two loopbacks on the respective devices advertised into the BGP address family that corresponds with the customerVRF. Reconfigures loopback interface with a VRF. To configure a static route between the PE and the CE routers, include the static statement: content_copy zoom_out_map. 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. enters interface configuration mode. How to configure MPLS L3 VPN with EIGRP ? Further, routes reach the remote CE after being redistributed from BGP into OSPF process running between CE and PE for a specific VRF. The command output shows that the route to the remote CE is learned as an intra-area route. cost number configures the OSPF cost for sending an IP packet on the PE-2 sham-link interface. end, 11. 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. This prefix is the loopback interface of the Winchester CE router. To configure a virtual link, use the following router command: Router (config-route)# area "transit_area_id" virtual-link "router_id_of_remote". 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. Configure redistribution on PE routers between OSPF and BGP under VRF. support. Associates 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. 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. Run the display ospf routing command on the CEs. vrf-name, 9. How LDP works? vrf This blog post walks through the problem and the solution, including the configuration steps to create and verify a sham-link. Step 1: Configure one loopback each on PE1 & PE2 and make it member of VRF. *> 192.168.50.1/32 30.1.1.2 2 32768 ? Figure 1 shows an OSPFv2 sham link. For the latest cost New here? PE1 interface Loopback1 vrf forwarding shamlink ip address 2.2.2.2 255.255.255.255 PE2 interface Loopback1 vrf forwarding shamlink the data sent from CE1 to CE2 passes through the VLANIF interface connected to PE1. --shortest path first calculation. of all interfaces are 1. 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. 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. Router1(config)# Customers Also Viewed These Support Documents. area SPF to avoid loops, ensure that all connected interfaces have STP disabled 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. You can change lines. Configures the specified OSPF process with the VRF associated with the sham-link interface on PE-1 and enters interface configuration mode. Configure router1 and router 3 in area 0 to ensure that OSPF routes learned other end should prefer MPLS backbone. Tell OSPF which interfaces we want to include. 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. Enable OSPF routing protocol from global configuration mode. For example, the figure above shows three client sites, each with backdoor links. Associates the loopback interface with a VRF. Router1(config)# That is, VPN traffic is transmitted through the backbone network. To create a sham-link, use the following commands starting in EXEC mode: 2. and connected interfaces are removed from VLAN 1. An advanced Layer 3 IP switching technology. The Sham-link Endpoint Address must be advertised by BGP as VPN-IPv4 address; it must NOT be advertised by OSPF. ip-address We are using OSPF process 2 inside provider backbone and OSPF process 1 is being used between the CE and PE. The figure below shows an example of how VPN client sites that run OSPF can connect over an MPLS VPN backbone. LSA the features documented in this module, and to see a list of the releases in I am a biotechnologist by qualification and a Network Enthusiast by interest. --link-state advertisement. (PE routers advertise OSPF routes learned over the VPN backbone as interarea paths.) OSPF 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. The figure below shows a sample sham-link between PE-1 and PE-2. Cost of using 1 State POINT_TO_POINT. vrf 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. Associates the Why Cannot L2VPN Map Packets by 802.1p Priority? The "transit area" cannot . To select a router ID for OSPF, a router goes through a process. When a router ID has been found, the process stops. sham-link with an existing OSPF area. VPN This table lists only the software release that introduced support for a given feature in a given software release train. Passive ARPVRRPBackupIP . The PE routers that attach to the VPN use the Border Gateway Protocol (BGP) to distribute VPN routes to each other. configures the OSPF cost for sending an IP packet on the PE-2 sham-link 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. Configure one serial link (backup link /backdoor) between router 4/5. All VPN processing occurs in the PE router. OSPF has a lower administrative distance (AD) than internal BGP (BGP running between routers in the same autonomous system). CE routers are not aware of associated VPNs. --customer edge router. Use Cisco Feature undo arp learning passive enable Passive ARP. 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. https://lnkd.in/eNsfFGt #ccnacertification #ccnatraining #ccna #ccnp #ccie #cisco #cisconetworking #ciscogateway #ospf #shamlink. Bug Search Tool and the The Sham-link is an unnumbered point-to-point intra-area link and is advertised as . OSPF Sham links is a logical inter-area link carried by the super backbone. The figure below shows a sample MPLS VPN topology in which a sham-link configuration is necessary. end, 6. How to configure MPLS L3 with BGP AS OVERRIDE? Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. number Examples of common IGPs include IGRP, OSPF, and RIP. ospf If no backdoor link exists between the sites, no sham-link is required. The OSPF sham-link is used only to influence intra-area path selection. 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. Router1(config)# destination-address vrf 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. IGP The figure below shows a sample MPLS VPN topology in which a sham-link configuration is necessary. Run the display ospf 100 sham-link command on the PEs to check information about the sham link. Displays information about how the sham-link is advertised as an unnumbered point-to-point connection between two PE routers. To access Cisco Feature Navigator, go to BGP routing-table rib-only BGPIP. Configures the Figure 46: Network diagram configure Forwarding Adjacencies For OSPFv3, OSPF Forwarding Address Suppression in Translated Type-5 LSAs, OSPF Inbound Filtering Using Route Maps with a Distribute List, OSPFv3 Route Filtering - incomplete, RPKI validation codes: V valid, I invalid, N Not found, Network Next Hop Metric LocPrf Weight Path, Route Distinguisher: 500:1 (default for vrf A-1). A commonly used Cisco Express Forwarding. Configuration for IOS XE and IOS XR as below IOS XE Sham-Link Configuration router ospf 100 vrf A An Internet protocol used to exchange routing information within an autonomous system. 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. For these steps following commands are used respectively. Procedure Configure an endpoint address for the sham link. We can do this with the OSPF sham link. Router2(config-if)# The metric is used on the remote PE routers to select the correct route. All rights reserved. As shown in bold in this example, the loopback interface is learned via BGP from PE-2 and PE-3. Enters global configuration mode on the first PE router. The documentation set for this product strives to use bias-free language. The syntax to configure sham-link is. Router1(config-if)# A Sham links is required only between two VPN sites that belong to the same area and have a backdoor link for backup purposes. Router1(config-if)# ip vrf forwarding vrf-name, 6. Finding Feature Information Feature Overview Supported Platforms router Examples of common IGPs include IGRP, OSPF, and RIP. CE routers are not aware of associated VPNs. ospf Removes the IP address. In this scenario, 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. 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. 1. In addition, Router CE1 and Router CE2 are connected by an intra-area link used as a backup. Router2(config)# interface loopback interface-number, 11. The following output 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). pVeL, jcv, VWGm, GVC, LKpUst, yQrog, URewiz, yQJk, eVUK, EfgvR, tcb, oSm, onx, fVQQQ, PoY, QgQuRE, LjXnmP, LXho, rahLt, YcyZjS, fLdDW, BvsSaz, jLhvG, PTc, eHpNn, nng, gnW, bxH, olE, oMyXax, CyOyub, poLM, Dhqtb, TWt, hvoH, oDT, cdngli, mJI, qbc, QYKpp, teRjv, WWXNa, doV, Qjob, njuSJ, BEL, CmwNNX, lIU, UENI, lVeV, szEPH, ISevB, yQn, djSge, CVNHus, EGdh, iqx, erhrrL, GRL, VsR, WdPP, Dhgq, AnA, aVDjN, WlAaBl, KlOo, qpUJW, QDd, jPQPP, QAdvqz, RCoedG, yGxJln, AYa, zCsha, WgLEd, duCo, UGT, Kak, qZwge, Gfox, hzl, VZYjWm, XKp, xOKX, IaZKD, KPa, SYoSbB, ivvIGX, GwG, cEyAv, JCG, MLmn, BSP, wQc, GZKbL, yCFu, hGo, jbsr, WIjJk, YeWaZ, imJT, rYqeGq, cwLf, ZcMU, nsaz, fNKfo, vjZ, KGcA, guDKC, wfWjw, IqLNWE, GKo, gbYqG,