[ale] Advanced Routing for Dummies

Leonard Thornton Leonard at Intelis-inc.net
Fri Apr 13 18:07:45 EDT 2001

OK sports fans...I'm in over my head and need help.

I have an internal private network and two public networks.

Local Network "A"
Public Network "B" (T1 connection, 16 static IP addresses)
Public Network "C" (iDSL, 13 static IP addresses)

I have a Linux / RH7.0 / ipchains firewall with three (3) NICs (3C509) 
which connects the three networks.
"A" = eth0 (NAT)
"B" = eth1
"C" = eth2

My internal network uses the firewall NIC eth0 as it's default gateway.  No 

The issues I have:  Network "B" sees Network"C" only through the public 
network connection, not my firewall (and vice versa).  If I lose wither my 
T1 or my iDSL feed, "B" and "C" cannot talk to each other.  Additionally, 
if I lose my T1, I have to manually repoint my internal LAN traffic to the 
iDSL public connection.  I know there is a way for "B" and "C" to route to 
each other through the firewall rather than externally, but I have yet to 
find the magic incantation.  Additionally, is there a way to set up the 
routing so that my T1 is the preferred path for my internal network, and 
yet have traffic automatically go out the iDSL side if the T1 fails?

I have read FAQ's / HOW-TO's / Magic scrolls until I can't see anymore.  I 
do not have the time or energy to become a routing expert and am really 
just looking for an easy solution to set this up and walk away.  Has anyone 
done this before and can you tell me SPECIFICALLY how you accomplished this?

Thanks in advance.


The difficult while you wait.....the impossible overnight.

Leonard Thornton
Intelis, Inc.
5960 Crooked Creek Rd
Suite 30
Norcross, GA  30092

Office: 770.825.0032
Fax:            770.825.0028
Cellular:       404.583.5402
Pager:          888.785.9188
Email:          Leonard at Intelis-Inc.net

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