BGP Failover Question

Brian Johnson bjohnson at drtel.com
Mon Feb 21 15:21:45 CST 2011


Chris,

The best way to resolve this issue is to not use a service provider who takes down your connectivity outside of maintenance windows, but I digress.

This is the nature of BGP. You send your providers routes about your network prefixes and they send you routes to say the DFZ. When you forward packets to them ,because they sent you routes saying they can get the destinations your packets have on them, it is now outside of anything you can do about it. It is now up to the peer to forward the packets as they said they would by sending you prefixes.

This is a trust relationship as you trust they will forward your packets because that is why you are paying them.

- Brian J.

-----Original Message-----
From: Chris Wallace [mailto:lists at iamchriswallace.com] 
Sent: Monday, February 21, 2011 3:10 PM
To: NANOG
Subject: BGP Failover Question

I am looking for some help with an issue we recently had with one of our BGP peers recently.  I currently have two DIA providers each terminated into their own edge router and I am doing iBGP to exchange routes between the two edge routers.  Last week Provider A made a policy change "somewhere" in their network in the middle of the day causing traffic to stop routing.  Of course this connection happens to be the preferred route for the majority of our inbound and outbound traffic.  I never saw our physical link go down and never saw our peer drop therefore BGP did not stop advertising routes, this caused most of our customers traffic to go nowhere.  In order to fix the issue I had to manually shutdown the peer till Provider A confirmed the change they made had been reverted.  This isn't the first time we have seen this issue with our various providers, how can I prevent issues like this from happening in the future?

---Chris




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