Cisco2621XM act as ethernet router?

[ddicky]

I have a dial-up modem for adsl connection and it only meant for single user and I wonder if I put in Cisco2621XM behind the adsl modem how should I configure the routing for enabling multiusers and doing NAT on the CIsco 2621XM

[tepatel]

I assume that you have adsl line connected to the isp provided adsl modem for one user only. You want to have that connection shared between more then one user using NAT.

First you need to some information like

1)Does that one user/PC getting dynamic ip address or static ip address?

2)Do you have installed any software on the PC to get access to internet?

3)How the adsl line is configured..like PPPoA, PPPoE, 1483 Bridging etc.

Based on the answers of above questions, you can configure 2621XM to get the ip address the way PC is getting and then do NAT over it.

OR

you can replace the adsl modem provided by isp with 2621XM and use WIC-1ADSL card to terminate adsl line there.

[ddicky]

Yes correct you are right,I'm using PPPoE,dynamic IP addresses for workstation and there is no software on the pc to access internet.As you explained how should I configure my Cisco2621XM to do NAT ,routing and act as a broadband router from the 2 Fastethernet 10/100 ports.

[#4]

tepatel is correct in stating that if you wish to use ONLY the 2621 and the DSL line and achieve NAT for host you must purchace a WIC and possibly a NM for the 2621 to achieve this.

As tepatel is a CCIE with Cisco he may not have mentioned another approach (no slam intended).

You may be able to achive your goals through the use of low-end, home-office, specific gear that permits NATing through a DHCP vendor provided IP address (singular). These are marketed as Cable/DSL routers through Asante, Linksys and others for $100 or so. These devices permit multiple internal devices with discreate internal IP addresses and services to access the internet through the one dynamic IP that your DSL/cable vendor is providing you.

The caveat here is that PAT (Port address translation) not true NAT (network address translation) is being used, and there are several services that WILL NOT WORK through PAT.

If you wish to be globally available, and have true IP connectivity from multiple host for multi-service, you're going to have to pay the ISP. If you wish to circumvent the limitations of the Dynamic client ONLY nature of your DSL connection this and several Dynamic DNS providers will allow you to do so.

Please note that by utilizing these workarounds to host commercial services your ISP, per your contract, may have legal reason to terminate your connection.