Dual Homed BGP
Blake Hudson
blake at ispn.net
Fri Jan 24 23:10:08 UTC 2020
On 1/23/2020 6:01 PM, Brian wrote:
> Hello all. I am having a hard time trying to articulate why a Dual
> Home ISP should have full tables. My understanding has always been
> that full tables when dual homed allow much more control. Especially
> in helping to prevent Async routes.
Brian, you're correct that having more routing information will give you
more control over routing decisions. However, for me, it's not about
control/traffic engineering but about basic redundancy/availability.
Taking full tables gives you visibility into whether an actual path
exists (or does not exist) via each of your upstream providers. If you
just take a default route originated by your peer you'll only have
visibility that there's a connection between your router and your peer -
not to the rest of the internet or to a specific destination past your
peer. As Job said, maintenance, router reboots, and other upstream
connectivity issues can cause an upstream peer to be missing routes that
the other peer might have.
In my experience, most folks multi-home for improved
redundancy/availability. So for those that are multi-homed, I recommend
taking full tables so that you can get the most benefit. This may come
at an additional expense so I understand why some would choose to take a
default route only.
--Blake
More information about the NANOG
mailing list