HELP - Firewall behinf a Cisco 837 router

Posted on 2006-04-23
Last Modified: 2013-12-14

I currently have a cisco 837 router connected to my DSL line.  This is working fine, it has an onboard firewall but not the best.  

I have just purchased a sonicwall TZ170, and need to position this behind the 837.  

We need to 837 as this has the built in Modem in it for the DSL.  I have an 8 external IP Addresses.

How do i do this?

I have thought of linkig the two up in another subnet i.e. but how would i configure the routing??

Thanks for you help!

Question by:jay_jones
    1 Comment
    LVL 2

    Accepted Solution

    The Cisco would sit on its external WAN IP addres for example

    set the wan interface of the firewall to : and then put its trusted (lan) interface on a range for your local network, the Firewall can do all the NAT'ing for local traffic and on the cisco 837 if you can configure the Fastethernet ports then just unnumber the dialer to a FE port example

    conf t
    interface FastEthernet0/0
     ip address
    interface Dialer1
     ip unnumbered FastEthernet0/0

    Check the subnet with your ISP for the correct IP allocation for your range of IP's


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