[c-nsp] IOS XR as-path-loopcheck and as-override

James Bensley jwbensley at gmail.com
Tue Oct 28 06:32:06 EDT 2014


Hi All,

I can't seem to get these features to work on my lab ASR9K1 running
4.3.4. I have two eBGP neighbours in AS 65001 both advertising a /32
loopback to the ASR9K (MPLS Opt B peerings). As per the output below
the ASR9K receives the /32 route from each eBGP neighbour.

I can't get the ASR9K to send the route from either eBGP neighbour in
AS 65001 to the other.

I have added "as-path-loopcheck out disable" under both
address-families under BGP and under the test VRF "vrf". I have also
configured "as-override" on one of the neighbours (192.168.1.6) in
both address-families.

I understand how both of those features work, I'm not sure whythough
despite enabling them everywhere out of desperation I still don't
advertise the /32 route from 192.168.1.2 to 192.168.1.6 in the test
VRF.

RP/0/RSP0/CPU0:ASR9001#show route vrf vrf1

L    10.0.0.1/32 is directly connected, 20:25:10, Loopback1
B    10.0.0.2/32 [20/0] via 192.168.1.6 (nexthop in vrf default), 00:08:53
B    10.0.0.3/32 [20/0] via 192.168.1.2 (nexthop in vrf default), 17:03:24

RP/0/RSP0/CPU0:ASR9001#show bgp vpnv4 unicast neighbors 192.168.1.6
advertised-routes

Network            Next Hop        From            AS Path
Route Distinguisher: 55555:1
10.0.0.1/32        192.168.1.5     Local           ?

Processed 1 prefixes, 1 paths

ASR9K:

router bgp 55555
 address-family ipv4 unicast
  as-path-loopcheck out disable
  allocate-label all
 !
 address-family vpnv4 unicast
  as-path-loopcheck out disable
 !
 neighbor 192.168.1.2
  remote-as 65001
  address-family ipv4 labeled-unicast
   route-policy PASS in
   route-policy PASS out
   send-extended-community-ebgp
   next-hop-self
  !
  address-family vpnv4 unicast
   route-policy PASS in
   route-policy PASS out
   next-hop-self
  !
 !
 neighbor 192.168.1.6
  remote-as 65001
  address-family ipv4 labeled-unicast
   route-policy PASS in
   route-policy PASS out
   as-override
   send-extended-community-ebgp
   next-hop-self
  !
  address-family vpnv4 unicast
   route-policy PASS in
   route-policy PASS out
   as-override
   next-hop-self
  !
 !
 vrf vrf1
  rd 55555:1
  address-family ipv4 unicast
   as-path-loopcheck out disable
   redistribute connected
   allocate-label all


Any help would be greatly appreciated as I expected I have overlooked
something really obvious.

Cheers,
James.


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