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OSPF route selection issue with 6PE/6VPE scenario


[Note: Its a duplicate post as I didn't get any response under MPLS category I am posting this question again under WAN category, Sorry for the trouble if any]

Hi Experts,

Using below topology for 6PE and 6VPE, Ipv6 prefix 60::6:6:6/128 on CE1 is advertised by PE1 using 6PE method on the MPLS backbone to PE2 and PE2 redistributes(OSPF) the same to CE3. On the other hand  PE1 advertises both 60::6:6:6/128 and 60::60:60:60/128 from CE2 using 6VPE method on MPLS VPN to PE3 and from there it redistributed(OSPF) to CE3. Both PE1 fa1/1 and PE3 fa1/0 are configured for same VRF with same RD/RT values. Now I could see both prefixes advertised by PE1 are reaching the respective egress PEs via BGP but on CE3  prefix 60::6:6:6/128 is installed as O E2 route (as its learned by 6PE method)  via PE2 instead of O IA route via PE3 (learned by 6VPE) 

By OSPF rule, O IA is better than O E2, then why CE3 chooses E2 route instead of IA for the same prefix? Can anyone explain this in detail?

Attaching all PE & CE routers config and routing/ospf database table.

R8-CE3#sh ipv6 route ospf
IPv6 Routing Table - default - 11 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, R - RIP, H - NHRP, I1 - ISIS L1
I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary, D - EIGRP
EX - EIGRP external, ND - ND Default, NDp - ND Prefix, DCE - Destination
NDr - Redirect, O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1
OE2 - OSPF ext 2, ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP

OE2 10::1:6:0/120 [110/1]
via FE80::C805:1EFF:FEF0:1C, FastEthernet0/0
OI 10::1:7:0/120 [110/2]
via FE80::C806:16FF:FEFC:1C, FastEthernet1/0
OE2 60::6:6:6/128 [110/1]
via FE80::C805:1EFF:FEF0:1C, FastEthernet0/0
OI 60::60:60:60/128 [110/2]
via FE80::C806:16FF:FEFC:1C, FastEthernet1/0

1 Reply 1

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee


I have replied in the MPLS thread as this topic is more relevant there:

Best regards,

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