nanog mailing list archives
Re: Dual Homed BGP for failover
From: William Herrin <bill () herrin us>
Date: Tue, 18 Jan 2011 14:00:30 -0500
On Tue, Jan 18, 2011 at 1:32 PM, Ahmed Yousuf <ayousuf0079 () gmail com> wrote:
It has now been requested to be able to distribute traffic across both links rather than preference traffic to the higher speed link. - Is this really a good idea, as the BGP process won't care what the utilisation of the links are and you will see situations where the lower speed link gets used even though the high speed link utilisation is 0?
Hi Ahmed, This really isn't an either/or situation. You can prefer the higher speed link without excluding the lower speed link. One common way to do this (there are better ones but this one is easy) is to prepend the AS path you send and receive on the lower speed link so that it's longer.
- If we are doing this, I don't want to take a full routing table, I would rather just take the ISPs routes and perhaps their connected customers. One ISP has said they will only provide full routing table or default. I really don't want to take a full table, is receiving default only going to be a problem for my setup?
IMO, that would be a mistake. Taking significantly less than a full table severely limits your options for balancing traffic between the links.
- Any advice on how to avoid situations where the low bandwidth link is being used even though there is 0 utilisation on the high bandwidth link?
Any particular communication is either going to go through one link or the other. I'm generalizing here, ignoring some subtleties, but if packets between two particular hosts have picked the low speed link, they will take that one instead of the high speed link. So in a sense it isn't possible to prevent that situation. However, you can adjust the preferences for one path versus the other so that you're not leaving either circuit underused overall and the disparity between your circuits (30 and 10) is not enough to cause major performance issues in and of itself. Regards, Bill Herrin -- William D. Herrin ................ herrin () dirtside com bill () herrin us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004
Current thread:
- Dual Homed BGP for failover Ahmed Yousuf (Jan 18)
- Re: Dual Homed BGP for failover Jack Carrozzo (Jan 18)
- Re: Dual Homed BGP for failover Max Pierson (Jan 18)
- RE: Dual Homed BGP for failover George Bonser (Jan 18)
- Re: Dual Homed BGP for failover William Herrin (Jan 18)
- Re: Dual Homed BGP for failover Jack Bates (Jan 18)
- RE: Dual Homed BGP for failover Brandon Kim (Jan 18)
- RE: Dual Homed BGP for failover George Bonser (Jan 18)
- Re: Dual Homed BGP for failover Jack Bates (Jan 18)
- Re: Dual Homed BGP for failover Jack Carrozzo (Jan 18)
- Re: Dual Homed BGP for failover Jack Bates (Jan 18)
- Re: Dual Homed BGP for failover Jack Carrozzo (Jan 18)
- Re: Dual Homed BGP for failover Max Pierson (Jan 18)
- RE: Dual Homed BGP for failover Ahmed Yousuf (Jan 19)
- RE: Dual Homed BGP for failover Randy McAnally (Jan 19)
- Re: Dual Homed BGP for failover Jack Bates (Jan 18)