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Blackhole Route in FIB

Valued Contributor

Blackhole Route in FIB

I'm having reachability issues in an BGP-L3VPN MPLS test environment, and I've noticed that the unreachable prefixes exist in the FIB with the Blackhole flag.



[LAB-PE3] dis ip routing-table vpn-instance TEST-VRF

Destinations : 24 Routes : 29

Destination/Mask Proto Pre Cost NextHop Interface BGP 255 0 HGE1/1/25 BGP 255 0 HGE1/1/25 BGP 255 0 HGE1/1/25 BGP 255 0 HGE1/1/25

[LAB-PE3] dis fib vpn-instance TEST-VRF

Destination count: 24 FIB entry count: 36

U:Useable G:Gateway H:Host B:Blackhole D:Dynamic S:Static
R:Relay F:FRR

Destination/Mask Nexthop Flag OutInterface/Token Label UBGR HGE1/1/25 24256 UBGR HGE1/1/25 24256 UGR 414 24117 UGR 414 24117


  • The above is taken from PE3.
  • PE1, PE2 and PE3 all connect directly to RR1.
  • PE1 is injecting the 10.66 prefixes and peers with the RR using a loopback IP (
  • PE2 is injecting the 10.64 prefixes and peers with the RR using the physical interface IP (
  • The 10.66 prefixes are reachable, the 10.64 ones are not.
  • Everyone blackholes PE2's routes.
  • PE3 has a FIB next-hop of for PE2s routes which is (PE3's next-hop on the RR)
  • If I change PE2 to "connect-interaface loopback X", then all the problems are resolved.

I can't work out why this is happening.

Any ideas?