[c-nsp] BGP - advertising default route to Branch offices

[Saku Ytti]

On Thu, 13 Aug 2020 at 03:25, Yham <yhameed81 at gmail.com> wrote:

> Can anyone please tell which is considered a best practice when it comes to
> the advertising default route? If any vendor documentation addresses this,
> please feel free to share.

In my opinion there is never a need to carry default route in dynamic
routing protocols, it's always inferior solution to static.

In this particular case, two options

1) BGP
a) Advertise some candidate route from BGP (like your PA aggregate,
which you originate from stable backbone boxes)
b) Recursive static default route in branch routers pointing to the PA
aggregate as next-hop

2) IGP
a) have loopback42 in every LSR/P box with same IP address, which you add to IGP
b) Recursive static default route in branch routers pointing to the
loop42 address as next-hop

In both cases isolated edge won't blackhole the the branch by
advertising default it doesn't have as well as you'll always choose
closest working exit.


-- 
  ++ytti