Awesome Antonio. Thanks! I am getting ready to start volume 2 so hopefully I have more input as we progress :)
On Tue, Jun 9, 2009 at 9:35 AM, Antonio Soares <[email protected]> wrote: > 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] > > > > -- Bryan Bartik CCIE #23707 (R&S), CCNP Sr. Support Engineer - IPexpert, Inc. URL: http://www.IPexpert.com
