Dual Homed BGP

Fri Jan 24 23:39:14 UTC 2020

On Fri, 24 Jan 2020, Baldur Norddahl wrote:

> Full tables will not make much noticeable difference if you are not peering. However you want to make sure both
> links get used. It can be a 90%/10% split but 100%/0% is bad because then you may discover that the alternate path
> is actually broken the moment the primary fail. If you choose only default then you need to think about that. 
> If you join any peering exchanges, full tables will be mandatory. Some parties will export prefixes and then expect
> a more specific prefix received from your transit to override a part of the space received via the peering. 

90/10 will suck when the link carrying 90% of your traffic needs more pipe 
and you have a ton of unused capacity on the other one.  Full tables from 
both providers gives you more options to tune things (assuming outbound is 
your larger direction).  If you're an eyeball provider and most of your 
traffic is inbound, your outbound traffic routing decisions aren't quite 
as relevant.

Have those suggesting "multihoming with two partial feeds and default 
routes" forgotten peering pissing matches, long lasting inter-network 
capacity issues, or that certain "tier 1" providers don't even 
have/provide a full v6 table?

If you're going to multihome, do it right, and get full routes from all 
your providers.

----------------------------------------------------------------------
  Jon Lewis, MCP :)           |  I route
  StackPath, Sr. Neteng       |  therefore you are
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