Dual Homed BGP for failover

Tue Jan 18 18:32:03 UTC 2011

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