Four T1s - 2 ISPs - One 7200 - Solution?

Hello,
I have just been given the task of combining Four T1s (3 from ISP A and
1 from ISP B) into a Cisco 7200.
(Lines were inherited from merger and are under contract...so we cant get
rid of them)
I am assuming that running BGP to load balance among them is the way to go.
Is it?

And how difficult of a project is this since my BGP skills are in the
novice-intermediate range.
(My routing skills are pretty good however. I just have really never had the
need for BGP in my past)

I am also wondering how much help/info you get from the ISP to set this up.

Any advice would be extremely helpful.
Thank you!

 

The load balancing can be broken down into two parts:

a) load balancing the traffic over the 3 T1 between your network and
ISP #1

b) load balaning the traffic between ISP #1 and ISP#2 on a 3:1 ratio



The easiest way to handle a is to configure the EBGP neighbors using
loopback address and static routes see Cisco document
http://cco.cisco.com/en/US/tech/tk365/tk80/technologies_configuration_example09186a00800945bf.shtml
Do not use the BGP weight attribute; use local preference sttribute
instead.


The second part is a little trickier. One of the ways to do this is to
set local preference for a set of major upstream AS numbers on the BGP
routes received from a particular ISP. So for example set local
preference for all UUNET routes to be routed over the three links to
ISP #1. Thus manipulating local preference affects OUTBOUND traffic.

Use AS path prepend for a subset of you address space for routes that
you advertise. Rember that a lot os ISP we not accept BGP routes
advertises for prefixes greater than /24s. If you have a small
address space this will be problematic.