Duplicated routes received from Route Reflectors

[Délsio Cabá]

Hi

Thanks for the response

I understand your point. I have added a third RR Server to check, and
it's adding a entry to the FIB. So if I have even 10 RR, it will add
10 entries on the FIB?

Why the cluster list is different?


RR-CLIENT#show ip bgp x.x.x.x
BGP routing table entry for x.x.x.x/29, version 1028
Paths: (3 available, best #1, table default)
  Not advertised to any peer
  Refresh Epoch 2
  Local
    10.10.10.6 (metric 5) from 10.200.2.126 (10.200.2.126)
      Origin IGP, metric 0, localpref 400, valid, internal, best
      Originator: 10.10.10.6, Cluster list: 10.200.2.126
      rx pathid: 0, tx pathid: 0x0
  Refresh Epoch 1
  Local
    10.10.10.6 (metric 5) from 10.200.2.124 (10.200.2.124)
      Origin IGP, metric 0, localpref 100, valid, internal
      Community: 2470510602
      Originator: 10.10.10.6, Cluster list: 10.200.2.124
      rx pathid: 0, tx pathid: 0
  Refresh Epoch 1
  Local
    10.10.10.6 (metric 5) from 10.200.2.125 (10.200.2.125)
      Origin IGP, metric 0, localpref 400, valid, internal
      Community: 2470510602
      Originator: 10.10.10.6, Cluster list: 10.200.2.125, 0.0.0.1, 10.200.2.126
      rx pathid: 0, tx pathid: 0

On Tue, Feb 2, 2021 at 4:43 PM Chriztoffer Hansen <ch at ntrv.dk> wrote:
>
> Hi,
>
> On Tue, 2 Feb 2021 at 09:37, Délsio Cabá wrote:
> > We have a installed 2 BIRD RR (10.200.2.125 and 10.200.2.124)  just
> > installed to use as reflectors on our network
> >
> > We noticed the client is adding 2 entries to the routing table.
> >
> > Is this normal?
> >
> > Taking into consideration we do full global BGP is will be too much
> > memory wasted:
> >
> > RR-CLIENT#show ip bgp 0.0.0.0
> > BGP routing table entry for 0.0.0.0/0, version 0
> > Paths: (2 available, no best path)
> >   Not advertised to any peer
> >   Refresh Epoch 1
> >   xxxx
> >     10.200.0.252 (inaccessible) from 10.200.2.125 (10.200.2.125)
> >       Origin IGP, metric 0, localpref 350, valid, internal
> >       Community: 2470515592
> >       Originator: 10.200.0.252, Cluster list: 10.200.2.125
> >       rx pathid: 0, tx pathid: 0
> >   Refresh Epoch 1
> >   xxxx
> >     10.200.0.252 (inaccessible) from 10.200.2.124 (10.200.2.124)
> >       Origin IGP, metric 0, localpref 350, valid, internal
> >       Community: 2470515592
> >       Originator: 10.200.0.252, Cluster list: 10.200.2.124
> >       rx pathid: 0, tx pathid: 0
>
> Yes.
> This is completely normal for IBGP RR clients. (Regardless if you are
> using BIRD or not)
> Your RR client receives one best-route from each RR (or RR cluster).
> Your RR client will install both routes in it's RIB.
> And the "best" route (decided locally by RR client configured logic)
> is installed in the FIB.
>
> You will want to have multiple routes for the same destination in your
> local RR client RIB. Should one of the RR's go offline. Being taken
> down for maint, etc. (= RR not available). Your RR client will then
> "fall-back" to the next best route it stores in it's RIB and install
> that in the FIB. Instead of the "now" gone best route. (In short,
> quicker failover to another route to the destination, and has high
> potential lessening the time traffic is potentially blackholed during
> a route convergence)
>
> --
> Cheers, Chriztoffer
>