[c-nsp] Cisco 7200's not importing prefixes when RT of ASN:VRF_ID used

[Stephen Fulton]

Hi all,

I am having difficulty with some older Cisco 7200's within a production 
MPLS network.  The others hosts are IOS-XE or IOS-XR based and there are 
no issues with those.  The problem devices, plural, are 7206's with 
several different versions of IOS, so I do not believe it is a bug but 
likely a configuration issue.

The issue I am facing is that route-targets formatted as ASN:VRF_ID are 
not being accepted by the 7200's.  Route-targets formatted as IP:VRF_ID 
are.  Example VRF configs:

! Non-working configuration on a 7200
vrf definition VRF999
  rd 1.0.0.1:999
  address-family ipv4
   route-target export 23456:999
   route-target import 23456:999

! Working configuration on a 7200
vrf definition VRF999
  rd 1.0.0.1:999
  address-family ipv4
   route-target export 1.0.0.1:999
   route-target import 1.0.0.2:999
   route-target import 1.0.0.3:999
   (etc)

All other participating devices will see prefixes exported from the 
7200's when ASN:VRF_ID is used, but the 7200 will not see any prefixes 
which should be imported when using ASN:VRF_ID.

When IP:VRF_ID is used, all is well, however I cannot utilize that 
format without significant changes across the network, which is a very 
undesirable option.  I could potentially use route-target rewrite but I 
want to avoid that if possible as well.

What am I missing?  It has been almost a decade since I last ran into 
something like this, which is several networks ago and for the life of 
me I cannot recall and my Google-fu is failing.

Thanks,

Stephen

PS: I do have a BGP configuration for the VRF on the 7200's.. an example 
below.

router bgp 23456
  address-family vpnv4 uni
   neighbor 1.0.0.2 send-community both
   neighbor 1.0.0.3 send-community both
   (etc etc)
  address-family ipv4 vrf VRF999
   redistribute connected
   redistribute static