Friday, May 4, 2018

receiving IPv6 routes via eBGP problems with MPLS labels

I've setup eBGP peering over a BGP free core (CE to a route-reflector). All the IPv4 routes received are fine and once received I can traceroute to the IPv4 addresses over the BGP free core using MPLS. all good.

IPv6 however isn't working. The route-reflector is getting the IPv6 routes fine via eBGP but it doesn't look like it's appending an outgoing label so as soon as packets it leaves the route-reflector to the next hop it loops right back as the connected router has no idea about the route and as it's got no label it's not going via a LDP path.

If I look at the labels you can see the following:

IPV4 received route. All good, outgoing label seen.

R2#show mpls forwarding-table 123.64.12.0
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
None 8028 123.64.12.0/24 0 Te0/1/0 88.228.143.150

IPv6 however shows no outgoing label.

R2#show mpls forwarding-table 2A0X:XXC:6::/48
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
25044 No Label 2A0X:XXC0:6::/48 0 Te0/1/0 FE80::207:7DFF:FE75:7740

Now I think it's because it's trying to use the link-local address as it's next hop instead of one of the established LDP IP's which of course are all IPv4.

It's only the eBGP received routes it has this problem on. iBGP is fine, OSPF is fine.

Any of you guys seen this behavior. Any help greatly appreciated. thanks



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