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Filtering individual BGP communities

Sat Jun 09, 2018 6:59 am

Has anyone worked out a way to delete a specific BGP community?

We are present in 5 DCs where we have customers, peers and providers and set local preference on prefixes to prefer routes in that order.

Routers in each DC peer with local route reflectors, who in turn peer with route reflectors in each DC.

We wish to append a BGP community when route reflectors learn a route via a local DC client, to effect the following local preference within each DC:
local customer > customer > local peer > peer > local provider > provider

To avoid route oscillation, we essentially want to configure a filter to:
  • remove ibgp client community
  • if from local dc client, append ibgp client community

I only see a way to delete all communities, when a prefix matches a certain community. This currently makes it impossible to implement the following filters on the route reflectors:
eBGP appends comm_cust, comm_peer or comm_prov

reflectors:
del community comm_client
if msg from local DC client
  add community comm_client

if comm_cust in community
  set local-pref 200
if comm_cust and comm_client in community
  set local-pref 220
if comm_peer in community
  set local-pref 100
if comm_peer and comm_client in community
  set local-pref 120
if comm_prov in community
  set local-pref 50
if comm_prov and comm_client in community
  set local-pref 70

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