Routing to Multiple Inet Connections

I have a Linux box as my firewall/router with 3 NIC's; 1 NIC for LAN and 1 for each Inet connections.  I have an internal LAN with 2 routes to the Internet.  How do I set up routing to route to a selected Inet connection and somehow sense whether that connection is up and if connection is not up, route to the alternate connection?  Inet connections are 56K frame and 4Mbps.  I am using the Redhat 5.0 Distribution.
WARPHEADAsked:
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WARPHEADAuthor Commented:
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eckspurtCommented:
You can do that with gated, but you might find BGP a bit much to dive in to.  Your other option is to use custom scripts to detect the loss of one connection and switch your routing to the other.  An advantage to gated is that you could potentially set up preferential routing so that if both interfaces are up, you'd send traffic through whichever provider is closer to the destination.

Some documents to reference:

http://www.gated.merit.edu/
http://www.netaxs.com/~freedman/bgp.html
http://ds.internic.net/rfc/rfc1771.txt
http://www.hojmark.org/networking.html#rout

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WARPHEADAuthor Commented:
I am going to have to give you an A on this one.  Because, I seem to have not completely asked the whole question.  In addition to having two seperate routes to the internet...they are provided by two seperate service providers.  I should have asked how also to route my traffic via both.  My bust...  
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eckspurtCommented:
It's the same answer.  You need to use the Border Gateway Protocol (BGP) to talk to multiple providers.  Most big providers will be reluctant to talk to you via BGP because it's too easy to goof things up, but if you want to be multihomed, that's how you'd do it.

Just to drop the connection with one provider and switch to the other is simpler, tho' -- you could prob'ly do it with gated just fine, or you might find it easier to write a couple lines of shell script (or Perl) to switch.

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