Dual Homed BGP for failover

Max Pierson nmaxpierson at gmail.com
Tue Jan 18 12:54:34 CST 2011


You really limit yourself when you just take a default from a provider. If
you take 2 default's (one from each provider) for whatever reason, once you
change the local pref on one of them, it's all your traffic outbound or
none.

I always request a full table + default, so you can filter to best suit your
needs. This way, you can just accept /8's and get some sort of balancing  at
least (even if you just say all even /8's pref'd on one gateway and all odd
/8's from the other provider, etc). Of course this won't be symmetrical, but
thats the nature eBGP on the internet. You'll have to watch it and adjust as
needed so that you won't saturate your slower link.

Max

On Tue, Jan 18, 2011 at 12:32 PM, Ahmed Yousuf <ayousuf0079 at gmail.com>wrote:

> Hi,
>
>
>
> I'm looking at a setup where we use BGP to announce PI space to two
> upstream
> ISPs.  ISP A provides a 30Mb/s connection and ISP B provides a 10Mb/s.
> Originally the plan was to use ISP B's link as a backup and local pref
> traffic outbound via ISP A and pref  inbound using AS prepend via ISP A.
>  It
> has now been requested to be able to distribute traffic across both links
> rather than preference traffic to the higher speed link.  We are going to
> be
> using Juniper SRX210s to do this.  I have some questions:
>
>
>
> -          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?
>
>
>
> -          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?
>
>
>
> -          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?
>
>
>
> Thanks
>
>
>
> Ahmed
>
>



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