Introduction

On VPNv4 route reflectors, retain route-target is an RPL attachment point use for filtering which route-targets should be retained in the RIB.

Retain Route-Target

• By default route reflectors will hold all VPNv4 prefixes even with route-targets not locally imported.
• Using this feature only selected route-targets can be retained in the RIB and reflected out to clients.
• This feature is attached under bgp address-family vpnv4 of the bgp process.
• Only applicable to IOS-XR.
• Can also be used on ASBRs to import route-targets not locally defines in Inter-AS MPLS topology using Option B. Without setting retain route-target all on ASBRs no VPNv4 will be advertised to neighboring AS.

extcommunity-set rt VPN_A_ONLY
  100:2
end-set

route-policy RETAIN-RTs
  if extcommunity rt matches-any VPN_A_ONLY then
    pass
  endif
end-policy

router bgp 100
 address-family vpnv4 unicast
  retain route-target route-policy RETAIN-RTs
 !
!

Relevant XR Commands

retain route-target route-policy

RP/0/0/CPU0:XR1(config-bgp-af)#  retain route-target route-policy (RPL)

retain route-target all

Default configuration to retain all RTs.

RP/0/0/CPU0:XR1(config-bgp-af)#  retain route-target all

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