Dual Homed BGP for failover

Jack Carrozzo jack at crepinc.com
Tue Jan 18 12:40:56 CST 2011


You can just accept directly-connected peers from each network (or within 2
AS's, etc) then point a default at each one with different preferences. You
can do with with two edges if you like also: iBGP between the edges, and
push default into OSPF from both.

WRT dynamic load balancing... generally if your network is large enough for
two upstreams you'll have a pretty good distribution of flows so once you
get the prefs and prepends setup the way you like, thing won't shift that
rapidly. In my experience at least...

-Jack Carrozzo

On Tue, Jan 18, 2011 at 1:32 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
>
>



More information about the NANOG mailing list