Great Circle Associates Firewalls
(November 1996)
 

Indexed By Date: [Previous] [Next] Indexed By Thread: [Previous] [Next]

Subject: Routing in a network behind a firewall
From: Chris Michael <cm @ rmsbus . com>
Date: Thu, 28 Nov 1996 09:08:07 -0600
To: "'gauntlet-support @ tis . com'" <gauntlet-support @ tis . com>
Cc: Chris Michael <cm @ rmsbus . com>

I've got a question about how propagate routes behind a firewall.

Lets assume the network looks something like this:

                     ____________
                    | Internet   |
                    |  Gateway   |
                    |____________|
                       /            
                      /
               ______/__                               
              | Router  |                             
              |   A     |                              
              |_________|                              
              /          \   
             /            \     
            /              \      
    _______/____           _\__________
    | Router   |          |  Router    |
    |   A1     |          |    A2      |
    |__________|          |____________|


Without a firewall, in the normal course of events we'd run RIP (or
whatever) the routes would automagically appear.  The Internet gateway
would have a route to the world which would propagate to the other
routers.

If we insert a firewall, the picture becomes something like this.

                      
                     ____________
                    | Internet   |
                    |  Gateway   |
                    |____________|
                          |
                          |
                          |
                     _____|______
                    |            |
                    |  Firewall  |
                    |____________|
                       /            
                      /
               ______/__                               
              | Router  |                             
              |   A     |                              
              |_________|                              
              /          \   
             /            \     
            /              \      
    _______/____           _\__________
    | Router   |          |  Router    |
    |   A1     |          |    A2      |
    |__________|          |____________|



Assuming we don't run a routing protocol on the firewall, now what?  The
routers no longer "see" the Internet.  The only solution I could think
of was to put static routes on each of the routers & the firewall.  

So the firewall has a default route to the Internet and static routes to
each of the networks behind every router.  Router A1 has a default route
to the Firewall.  Routers A1 and A2 have default routes to Router A.

This solution works, but I'm wondering if there isn't a better way.  

Thanks,

Chris

-- 
christopher michael / rms business systems / cm @
 rmsbus .
 com 
Rid me, and deliver me from the hand of strange children, whose mouth
speaketh vanity, and their right hand is a right hand of  falsehood: --
Psalms



Indexed By Date Previous: Borderware with NT on SSN
From: Albert <alkl . pt @ cemtecasia . com . sg>
Next: Re: Cisco PIX
From: "Craig I. Hagan" <hagan @ cih . com>
Indexed By Thread Previous: NT Mailing List - Where can I find it?
From: "----> Jarnski <920145 @ balut . admu . edu . ph"
Next: Notes through Firewall misprint
From: Davyd Norris <Davyd . Norris @ fcollins . com . au>

Google
 
Search Internet Search www.greatcircle.com