[NTLUG:Discuss] OT: BGP anyone? (questions about dual ISPs and fault tolerance)

[Scott Womer]

I'm in a similar situation (but just the opposite), I recently brought in
another T1 from a 2nd ISP that was chosen because they have a completely
different route to the backbone than my 1st ISP.

I'm setting up BGP on my internal infrastructure to provide the best
outbound path to the internet.

I'm starting to look at options to provide automated fault tolerance and if
possible, some load balancing between the two on the incoming side.  I'd
like to hear from anyone that has already done this, and how you
accomplished it.

But I did have a specific question about your setup Jack.... did I read your
message right... you have the same class C subnet being routed to you by
both ISPs?  If this is true, could you tell me how this was accomplished.



Thanks,
Scott Womer




----- Original Message -----
From: "Jack Snodgrass" <idiotboy at cybermail.net>
To: <discuss at ntlug.org>
Sent: Thursday, June 21, 2001 6:51 PM
Subject: [NTLUG:Discuss] OT: BGP anyone? I've got two defaut routes and
don't know which to choose.


I have a PC ( network  actually, but let's just keep it simple. ) that has
two T1 connections
to two different ISP networks. Both of the T1 routers ( Cisco 1720 ) are
running BGP as set
up by the ISP people. The network is set up so that the Class C addresses
that we are using
come in on either T1.  Getting to my network over either T1 from the
internet is ok.

Going out is a different story. One option ( that I can think of ) is to use
a Linux box that has
access to both T1s. I'd like to have something ( BGP maybe ) that will let
the system decide
WHICH T1 to set up as the default route. Any machine on the network will
specify the
linux box as it's default route. The linux box will decide which T1 to use.
Do I need to set up
BGP... or is there something similar... but less complex/powerful that I'd
should use instead?

One of the ISP Techs said that I could run ihbgp ( something like that )
between the two
routers if I connected them up with a WIC card. Another ISP tech said that I
would
need a different, dual port Cisco router that I'd plug both T1s into. I
don't know if either
of them really knew what they were talking about.

I am 75% concerned with just Which Interface is up and operational. I'm 25%
concerned with
which interface is better for a particular conection or period in time.

I know that I can just set two default routes but I never have figured out
which one is used.
If one of the routes is 'unreachable', does it always go to the 'good' one
or is it 50/50 or
what?

Any info would be appreciated.

jack