Topology:PE – CE OSPF loop prevention mechanism – Field “meta TITLE=” MPLS/VPN PE – CE OSPF loop prevention mechanism Field “/> – metaExperiment aim: understand MPLS VPN CE, PE running OSPF preventive mechanism of loop Field – meta.According to the …
Topology:PE – CE OSPF loop prevention mechanism – Field “meta TITLE=” MPLS/VPN PE – CE OSPF loop prevention mechanism Field “/> – metaExperiment aim: understand MPLS VPN CE, PE running OSPF preventive mechanism of loop Field – meta.According to the above topology, traditional, when PR R2 routing heavy distributed to R1, R1 is the downbit bits with, when R1 spread route to downbit when R5 position, but also contains the role of ASBR R5 in R5 to R4, so the routing is through heavy distribution of learning, so it’s an lsa 5 kinds of routing, because the R4 R5 spread to downbit bits does not carry routing, such word, R3 will receive from the routing, again to R4, because produce the R2 loop.OSPF Tage Field is just to solve this loop and being designed.Principle: when R2 re-issued by into R1 shunts downbit bits with, not only, still contain meta field. Routing spread to R4 weight distribution, when R3 into R3 if you see the value of the field with meta routing, will it with their own AS number, if the same, compared by road would be rejected.Step 1. Configure the basicTo configuration of icon.R1:J lo 1.1.1/32 1-0S0/0:12. 1.1.1/24S0/1:15. 1.1.1/24R2:The lo 0-2. Laws 2.2.2/32S0/0:12. 1.1.2/24S0/1:23 turn. 1.1.2/24R3:The lo 3-0. 3.3.3 trace/32S0/0:23. 1.1.3/24S0/became 1.1.3/24 jR4:4.4.4/32 j lo 4-0 fromS0/0:34. 1.1.4/24S0/1:45. 1.1.4/24R5:0:5. Lo 5.5.5/32S0/0:45. 1.1.5/24S0/1:15. 1.1.5/24Step 2. Igp. ISIS ispR2:ISIS routerasp.net49.0001.2222.2222.2222.00Int s0/1The IP routerISISInt the lo 0The IP routerISISR3:ISIS routerasp.net49.0001.3333.3333.3333.00Int s0/0The IP routerISISInt the lo 0The IP routerISISStep 3. MPLSR2:IP cefMPLS label HTML 2999 2000MPLS label protocol LDPMPLS LDP router – id the lo 0Int s0/1MPLS IPR3:IP cefMPLS label. 3999 HTML 3000MPLS label protocol LDPMPLS LDP router – id the lo 0Int s0/0MPLS IPStep 4. Type VRF (variable refrigerant flowrate)R2:IP type VRF (variable refrigerant flowrate) vpnaRd 100:1Target are -100:1Int s0/0IP forwarding type VRF (variable refrigerant flowrate)vpnaR3:IP type VRF (variable refrigerant flowrate) vpnaRd 100:1Target are -100:1Int s0/1IP forwarding type VRF (variable refrigerant flowrate)vpnaStep 5. Ce igpR1:Router ospf 100Router – id1.1.1.1Asp.net 1.1.1.1 0.0.0.0Area 0Asp.net 12.1.1.0 0.0.0.255Area 0Asp.net 15.1.1.0 0.0.0.255Area 0R2:Vpna router ospf 100 type VRF (variable refrigerant flowrate)Router – id2.2.2.2Asp.net 12.1.1.0 0.0.0.255Area 0R3:Vpna router ospf 200 type VRF (variable refrigerant flowrate)Router – id3.3.3.3Asp.net 34.1.1.0 0.0.0.255Area 0R4:Router ospf 200Router – id4.4.4.4Asp.net 4.4.4.4 0.0.0.0Area 0Asp.net 34.1.1.0 0.0.0.255Area 0Asp.net 45.1.1.0 0.0.0.255Area 0Step 6. Mp – BGPR5:Router ospf 100Asp.net 15.1.1.0 0.0.0.255Area 0Router ospf 200Asp.net 45.1.1.0 0.0.0.255Area 0Ep-red ospf 100SubnetsR2:Router BGP 23No auNo syBGP router – id2.2.2.2No BGP defaultIpv4 – unicast3.3.3.3 nei remote – as233.3.3.3 neiUpdate – lo returned 0They – vpnv4′t3.3.3.3 neiActivateexitStep 7. RedistributableR3:Router BGP 23No auNo syBGP router – id3.3.3.3No BGP defaultIpv4 – unicast2.2.2.2 nei remote – as232.2.2.2 neiUpdate – lo returned 0They – vpnv4′t2.2.2.2 neiActivateexitR2:Router BGP 23They -’t ipv4Vpna type VRF (variable refrigerant flowrate)No auNo syEp-red ospf100exitVpna router ospf 100 type VRF (variable refrigerant flowrate)Ep-red BGP 23SubnetsStep 8. Observe meta – fieldR3:Router BGP 23They -’t ipv4Vpna type VRF (variable refrigerant flowrate)No auNo syEp-red ospf200exitVpna rotuer ospf 200 type VRF (variable refrigerant flowrate)Ep-red BGP 23SubnetsR4 # sh IP ospf external database1.1.1.1OSPF Router. 4.4.4.4) (ID (Process ID 200)Type – 5 AS External Link StatesThe LS: 9 age-relatedPC: (NoTOS – -, DC)LS Type: AS ExternalLinkLink State ID:External 1.1.1.1 (a by)Repeat Router:3.3.3.3LS Seq by:80000001Newer:0xFE7CLength: 36A goes:/32Metric Type: 2 (many state path) than any linkTOS: 0Metric: 650.0.0.0 Forward after:Are External meta:3489660951Can see from the RFC field format: meta0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 330 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 01+ – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – +| a | c | p l |ArbitraryTag|AutonomousSystem|+ – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – + – +Can see after 16 is AS number, can get,3489660951 binary: 110100000000000000000000000101110000000000010111 equals decimal after 16:, 2323 is the ISP, within, so when yard BGP R4 ISP received about R1 with the same AS the routing, will refuse to, so AS to avoid the scenario above the loopBy the following quote: http://blog.163.com/jesseprince@126/blog/static/16272530620105122056179/
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