Multi-homed implementation and BGP convergence time
sethm at rollernet.us
Fri Sep 11 22:54:37 UTC 2009
Andrew.Claybaugh at securian.com wrote:
> Hello - my company currently has two connections with a single tier 1 ISP.
> We are using the AS from our ISP at this time. In the next month we will
> be implementing a third connection with a second tier 1 ISP, so we will now
> be using our own AS number on all three routers. My question is when we
> implement the new connection and update our existing connections to use are
> own AS number, how much downtime will there be? So far the second ISP has
> only said that it could be hours for BGP to fully converge. We are looking
> for more detail about how long the outage will be and how widespread.
Hours? No way. It's more like minutes.
> Will it be relatively short to our customers that are on one of the ISPs we
> are directly connected to? Is downtime less for customers on other tier 1
> ISPs versus tier 2, etc. ISPs?
> We will only be receiving a default route on each of the three connections.
> Our routers will be advertising a small number of routes - 6 to 8.
I strongly encourage you to reconsider and take more than a default if
you're multihoming and your routers have enough memory. Remember to
create a full mesh on your BGP routers.
And as already said, if you're totally new to BGP and multihoming, hire
someone with experience in such matters to set it up.
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