peering between route reflectors

[Douglas Fischer]

Hello Benoit!

>From what you described, I imagine that there may be a confusion between
redundancy and load distribution.

You mentioned having a route-reflector per pop.
This is load distribution. Each such route-reflector will process route
exchanges with local peers.
And that is indeed a good thing!
Because it has positives like the fact that if you have 15-20 Peers in this
pop, even if this pop is isolated, the routes between these peers will
still be exchanged.
But it's also something that can be bad!
Because it will require that you have equipment that is chosen to perform
this Route-Reflector function.
It will also have different configurations to be applied on the routers in
the BGP peer part with the Route-Reflector. Each POP a configuration.

You also talked about establishing neighborhoods between Route-Reflectors.
This is also part of the concept of load sharing, and this is what will
make all POPs aware of all networks.

But putting a single Route-Reflector on each POP IS NOT redundancy!

>From what I could understand from what you described, if one of these
route-reflectors in these POPs becomes inoperative, the rest of the network
will continue operating... But during this inoperative time, the exchange
of routes between the Peers of the same POP (and with the other POPs on the
network) will not occur.

For you to have REDUNDANCE you would have to have 2 (or more)
Route-Reflectors DOING THE SAME ROLE. In your scenario, 2 in each POP.

And going a little further, and getting into a controversial topic, these 2
sets of Route-Reflectors COULD NOT exchange routes with each other!
Precisely to prevent, for example, a malformed route that affects the
functioning of one of the Route-Reflectors from being propagated to the
other and affecting that other route-reflector as well.


The recipe that I most often see being used for this type of scenario is to
have 2 Route-Reflectors in different geographic positions, positioned in
such a way as to be OFF-Path, thus trusting the IGP, and each one of them
peering with each network neighbor.

Em qua., 14 de jun. de 2023 às 17:04, Benoit Chesneau <
benoitc at enki-multimedia.eu> escreveu:

> For redundancy I am thinking to have a router reflector per pop . Each
> route reflector would peer with each others. The issue is that since each
> POP has a transit, i have duplicate route and sometimes a loop is created.
> How can it be prevented?? I tried to put them in the same cluster but it
> doesn't seem to be enough.
>
> Any idea is welcome :)
>
>
> Benoît
>
>

-- 
Douglas Fernando Fischer
Engº de Controle e Automação
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