Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Cable Modem + Router + Pix

Dear All,

Here's my problem:

I have a cable ADSL modem supplied by my ISP.

The ethernet cable is connected to ethernet 0 in my cisco 2621.

Router Ethernet 1 is directly connected to ethernet 0 (outside) of my pix 506E

Pix's ethernet 1 (inside) is connected to my backbone switch 3550 over a dedicated port VLAN

The pix is configured with nat.

My ISP gave me 6 external internet addresses. (/48)

One is given to the cable modem (configured remotely by the ISP)

one is given to the (external) ethernet 0 of the router

one is given to outside of the pix.

The problem is how to configure the router's interfaces since I don't want to configure nat between its interfaces and the (internal) ethernet 1 connected to the pix should be an internet address like ethernet 0.

Any solution is highly appreciated.

Thank you in advance,


New Member

Re: Cable Modem + Router + Pix

Hi Samir,

I am little unclear about the whole setup. Can you please elaborate with respect to the ip addresses? Your ISP has given you 6 ip addresses one is assigned to the e0 of the router. What is the ip address you are using for e1 of the router?

for e.g


.1 .2 ? ? ?



New Member

Re: Cable Modem + Router + Pix

Hello Syed,

First thank you for your reply.

Here's what's working now:

modem---------------------router-----------------------------switch(3550)-------------LAN 16.18 22.1 21.0

What I want to do:


Please what ip addresses should I configure on ethernet interfaces of all devices taking the following in mind:

- router: Cisco 2621 12.2 with NM-8AM module (for dial in access)

- pix: 506E (6.22 image and 2.1 PDM)

- switch: 3550 with EI

- LAN: this is my DMZ (from DMZ to LAN there's ISA server - working fine)

- Internet IP @:

- I want to publish my pix internet address for VPN access

- Also I want to publish a web server which is in the DMZ (LAN here)

IP @ Recap:

ADSL Modem (to internet) :

Router :

FastEth0 (to ADSL modem)

FastEth1 (to switch)


Multiple VLANS

DMZ VLAN: (connected to router) and default route

Many thanks in advance.


CreatePlease login to create content