Symptom
Label collision for the per-vrf label can be seen if lsd connection with bgp flaps.
It will cause traffic drop for prefixes in that vrf.
Conditions
Issue will happen if following events happen in chronological order:
1) In steady state bgp has allocated label L1 for vrf VRF1 with per-vrf label mode on.
2) LSD connection goes down.
3) All prefixes in the vrf VRF1 gets withdrawn.
4) LSD connection comes up.
5) BGP doesn't now reclaim label L1 from lsd. (At this point lsd thinks label L1 is free for use.)
6) Prefix gets learned in VRF1. BGP thinks label L1 is active and starts using it.
7) LSD assigns label L1 to someone else. Lets's say some other vrf in bgp.
This causes label collision.
Workaround
LSD connection with BGP shouldn't flap often.
If there is situation when connection is flapping then make sure there is at least one prefix in vrf to prevent this issue.
Further Problem Description
This is applicable to all platforms and all previous releases.
