Gday Antonio.
This is truly strange.
I copied your configs verbatim into my routers and I still can't
manage to re-create the problem.
R1#sh ip ospf neighbor 8.8.8.8 | inc Neigh|up
Neighbor 8.8.8.8, interface address 8.8.8.8
Neighbor priority is 0, State is FULL, 6 state changes
Neighbor is up for 00:07:51
The Sham Link is stable.
I'm keen to get to the bottom of it in case it happens in a lab!
Let's take this offline and report back to the group if we figure it out?
Con.
On Tue, Jul 28, 2009 at 7:02 PM, Antonio Soares<[email protected]> wrote:
> Hello Con,
>
> I was able to reproduce the problem:
>
> ++++++++++++++++++++++++++++
> R1#sh ip route vrf VPNB 8.8.8.8
> Routing entry for 8.8.8.8/32
> Known via "bgp 125", distance 200, metric 0
> Tag 678, type internal
> Redistributing via ospf 39
> Advertised by ospf 39 subnets
> Last update from 6.7.8.8 00:00:23 ago
> Routing Descriptor Blocks:
> * 6.7.8.8 (Default-IP-Routing-Table), from 125.125.125.2, 00:00:23 ago
> Route metric is 0, traffic share count is 1
> AS Hops 1
> Route tag 678
> MPLS Required
>
> R1#
> 01:04:03: %OSPF-5-ADJCHG: Process 39, Nbr 8.8.8.8 on OSPF_SL0 from FULL to
> DOWN, Neighbor Down: Interface down or detached
> R1#
> R1#sh ip route vrf VPNB 8.8.8.8
> Routing entry for 8.8.8.8/32
> Known via "ospf 39", distance 110, metric 1
> Tag Complete, Path Length == 1, AS 678, , type extern 2, forward metric 1
> Redistributing via bgp 125
> Last update from 6.7.8.8 00:00:05 ago
> Routing Descriptor Blocks:
> * 6.7.8.8 (Default-IP-Routing-Table), from 8.8.8.8, 00:00:05 ago
> Route metric is 1, traffic share count is 1
> Route tag 3489661606
>
> R1#
> R1#
> 01:04:16: %OSPF-5-ADJCHG: Process 39, Nbr 8.8.8.8 on OSPF_SL0 from LOADING to
> FULL, Loading Done
> R1#
> R1#sh ip route vrf VPNB 8.8.8.8
> Routing entry for 8.8.8.8/32
> Known via "bgp 125", distance 200, metric 0
> Tag 678, type internal
> Redistributing via ospf 39
> Advertised by ospf 39 subnets
> Last update from 6.7.8.8 00:00:11 ago
> Routing Descriptor Blocks:
> * 6.7.8.8 (Default-IP-Routing-Table), from 125.125.125.2, 00:00:11 ago
> Route metric is 0, traffic share count is 1
> AS Hops 1
> Route tag 678
> MPLS Required
>
> R1#
> ++++++++++++++++++++++++++++
>
> The link between R3 and R9 is shutdown.
>
> I am using 12.2(25)S13 in all routers in this lab.
>
> The relevant configs:
>
> R1:
> !
> interface Loopback1000
> ip vrf forwarding VPNB
> ip address 1.1.1.1 255.255.255.255
> no clns route-cache
> !
> router ospf 39 vrf VPNB
> log-adjacency-changes
> area 0 sham-link 1.1.1.1 8.8.8.8
> redistribute bgp 125 subnets
> network 31.3.1.1 0.0.0.0 area 0
> !
> router bgp 125
> bgp router-id 125.125.125.1
> bgp always-compare-med
> no bgp default ipv4-unicast
> bgp log-neighbor-changes
> neighbor 125.8.1.8 remote-as 678
> neighbor 125.125.125.2 remote-as 125
> neighbor 125.125.125.2 update-source Loopback0
> neighbor 125.125.125.5 remote-as 125
> neighbor 125.125.125.5 update-source Loopback0
> !
> address-family ipv4 vrf VPNB
> redistribute connected
> redistribute ospf 39 vrf VPNB match internal external 1 external 2 route-map
> ospf2bgp
> no auto-summary
> no synchronization
> exit-address-family
> !
> route-map ospf2bgp permit 10
> set origin egp 1
> !
>
> R8:
> !
> interface Loopback1000
> ip vrf forwarding VPNB
> ip address 8.8.8.8 255.255.255.255
> no clns route-cache
> !
> !
> router ospf 39 vrf VPNB
> log-adjacency-changes
> area 0 sham-link 8.8.8.8 1.1.1.1
> redistribute bgp 678 subnets
> network 98.9.8.8 0.0.0.0 area 0
> !
> router bgp 678
> bgp router-id 6.7.8.8
> bgp always-compare-med
> no bgp default ipv4-unicast
> bgp log-neighbor-changes
> neighbor as678 peer-group
> neighbor as678 remote-as 678
> neighbor as678 password ipexpert
> neighbor as678 update-source Loopback0
> neighbor 6.7.8.6 peer-group as678
> neighbor 6.7.8.7 peer-group as678
> neighbor 125.8.1.1 remote-as 125
> !
> address-family ipv4 vrf VPNB
> redistribute connected
> redistribute ospf 39 vrf VPNB match internal external 1 external 2
> no auto-summary
> no synchronization
> exit-address-family
> !
>
> I don't remember very well but i think i also loaded R1 and R8 with 12.0S and
> 12.4 and got the same results.
>
> And i'm using the same process id in R1 and R8. But even with different
> process ids, the problem still happens.
>
>
> Regards,
>
> Antonio Soares, CCIE #18473 (R&S)
> [email protected]
>
> -----Original Message-----
> From: Con Spathas [mailto:[email protected]]
> Sent: domingo, 26 de Julho de 2009 9:29
> To: Antonio Soares; [email protected]
> Subject: Re: [OSL | CCIE_SP] VOL2 - Section 1 - Task 8.2
>
> Gday Antonio,
>
> I've tried to re-create the issue you described below with no luck:
>
> 10.10.18.1/32 is the R1 loopback interface for the Sham
> 10.10.18.8/32 is the R8 loopback interface for the Sham
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> R1#sh ip ospf neighbor 98.9.8.8 | inc Neighbor|interface
> Neighbor 98.9.8.8, interface address 10.10.18.8
> In the area 0 via interface OSPF_SL0
> Neighbor priority is 0, State is FULL, 6 state changes
> Neighbor is up for 00:21:00
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> R1#sh ip ospf database | beg Type-5
> Type-5 AS External Link States
>
> Link ID ADV Router Age Seq# Checksum Tag
> 4.0.0.4 31.3.1.1 1325 0x80000001 0x009E9A 3489661053
> 10.10.18.1 98.9.8.8 1282 0x80000001 0x004D4A 3489661606
> 10.10.18.8 31.3.1.1 1279 0x80000001 0x00E82A 3489661053
> 11.0.0.11 31.3.1.1 1279 0x80000001 0x00FC2E 3489661053
> 54.5.4.0 31.3.1.1 1325 0x80000001 0x00D130 3489661053
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> R1#sh ip route vrf VPNB 10.10.18.8
> Routing entry for 10.10.18.8/32
> Known via "bgp 125", distance 200, metric 0
> Tag 678, type internal
> Redistributing via ospf 125
> Advertised by ospf 125 subnets
> Last update from 6.7.8.8 00:21:34 ago
> Routing Descriptor Blocks:
> * 6.7.8.8 (Default-IP-Routing-Table), from 125.125.125.2, 00:21:34 ago
> Route metric is 0, traffic share count is 1
> AS Hops 1
> Route tag 678
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> R8#
> R8#sh ip ospf neighbor 31.3.1.1 | inc Neigh|inter
> Neighbor 31.3.1.1, interface address 10.10.18.1
> In the area 0 via interface OSPF_SL0
> Neighbor priority is 0, State is FULL, 6 state changes
> Neighbor is up for 00:22:02
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> R8#sh ip ospf data | beg Type-5
> Type-5 AS External Link States
>
> Link ID ADV Router Age Seq# Checksum Tag
> 4.0.0.4 31.3.1.1 1386 0x80000001 0x009E9A 3489661053
> 10.10.18.1 98.9.8.8 1338 0x80000001 0x004D4A 3489661606
> 10.10.18.8 31.3.1.1 1341 0x80000001 0x00E82A 3489661053
> 11.0.0.11 31.3.1.1 1 (DNA) 0x80000001 0x00FC2E 3489661053
> 54.5.4.0 31.3.1.1 1386 0x80000001 0x00D130 3489661053
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> R8#sh ip route vrf VPNB 10.10.18.1
> Routing entry for 10.10.18.1/32
> Known via "bgp 678", distance 200, metric 0
> Tag 125, type internal
> Redistributing via ospf 678
> Advertised by ospf 678 subnets
> Last update from 125.125.125.1 00:22:34 ago
> Routing Descriptor Blocks:
> * 125.125.125.1 (Default-IP-Routing-Table), from 6.7.8.7, 00:22:34 ago
> Route metric is 0, traffic share count is 1
> AS Hops 1
> Route tag 125
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> As you can see the Sham-Link is stable, however I have not manipulated
> the Domain-Tag as shown in the OSPF database.
>
> Tag 3489661606 = 11010000000000000000001010100110
> 1010100110 = AS 678
>
> Tag 3489661053 = 11010000000000000000000001111101
> 1111101 = AS 125
>
> I tried this with 12.0S and 12.4Mainline code.
>
> Cheers,
> Con.
>
>
>>I found the solution to this problem !
>>
>>When we have a sham-link inside the same AS, there's no issues with routing
>>loops with the sham-links because the external LSA will
>>have the same route-tag.
>>
>>When we have a sham-link between two AS's, and the sham-links are advertised
>>by
>>eBGP, there's no problem because the eBGP AD is
>>lower than OSPF.
>>
>>But when we have a sham-link between two AS's and the sham-links are
>>advertised
>>by iBGP, there's a routing loop. The routers will
>>prefer the OSPF learned route instead of the iBGP because of lower AD.
>>
>>So the solution is to use the same "domain-tag" under the OSPF process in both
>>PE's.
>>
>>
>>
>>
>>Regards,
>>
>>Antonio Soares, CCIE #18473 (R&S)
>>[email protected]
>>
>>-----Original Message-----
>>From: [email protected]
>>[mailto:[email protected]] On Behalf Of Antonio Soares
>>Sent: segunda-feira, 8 de Junho de 2009 19:08
>>To: [email protected]
>>Subject: [OSL | CCIE_SP] VOL2 - Section 1 - Task 8.2
>>
>>My sham-link is flaping. As soon as the sham-link comes up, R1 and R8 start
>>prefering the OSPF route instead of the iBGP route. I
>>never saw this problem in regular MPLS VPNs inside one AS. In this because we
>>have an Inter-AS MPLS VPN scenario ?
>>
>>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>R1#
>>00:03:31: %OSPF-5-ADJCHG: Process 39, Nbr 8.8.8.8 on OSPF_SL0 from LOADING to
>>FULL, Loading Done
>>R1#
>>R1#sh ip route vrf VPNB | inc 8.8.8.8
>>B 8.8.8.8 [200/0] via 6.7.8.8, 00:00:14
>>R1#
>>R1#
>>00:03:47: %OSPF-5-ADJCHG: Process 39, Nbr 8.8.8.8 on OSPF_SL0 from FULL to
>>DOWN, Neighbor Down: Interface down or detached
>>R1#
>>R1#sh ip route vrf VPNB | inc 8.8.8.8
>>O E2 8.8.8.8 [110/1] via 6.7.8.8, 00:00:00
>>R1#
>>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>R8#
>>00:06:28: %OSPF-5-ADJCHG: Process 39, Nbr 1.1.1.1 on OSPF_SL0 from LOADING to
>>FULL, Loading Done
>>R8#
>>R8#sh ip route vrf VPNB | inc 1.1.1.1
>>B 1.1.1.1 [200/0] via 125.125.125.1, 00:00:13
>>R8#
>>R8#
>>00:06:44: %OSPF-5-ADJCHG: Process 39, Nbr 1.1.1.1 on OSPF_SL0 from FULL to
>>DOWN, Neighbor Down: Interface down or detached
>>R8#
>>R8#sh ip route vrf VPNB | inc 1.1.1.1
>>O E2 1.1.1.1 [110/1] via 125.125.125.1, 00:00:02
>>R8#
>>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>
>>After a few hours trying to understand why this was happening, i was able to
>>make it work tweaking the OSPF AD for the External
>>routes in R1 and R8.
>>
>>Anyone saw this problem in this lab ?
>>
>>And why in the PG we don't see the sham-link interfaces in R3 and R9 ?
>>
>>
>>Regards,
>>
>>Antonio Soares, CCIE #18473 (R&S)
>>[email protected]
>>
>
>
>
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