Which ethernet expansion card do I need?

Unanswered Question
Apr 11th, 2007

Hi all,

I have a Cisco 1720 router. The only expansion card I have in it right now is a WIC1DSUT1 card. I am trying to configure this router with a cable modem with Comcast service. Which ethernet expansion card do I need?


I have this problem too.
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desai.jaideep Thu, 04/12/2007 - 00:48


You can buy one WIC-ENET card.

The second thing you can do is connect both the ethernet from ComCast Modem and the router to a single switch. The configure dot1q encap on the fe of 1720.Give both the IPs and this will do for u.



nammysu88 Thu, 04/12/2007 - 06:35


Are you saying that I can get away with buying a WIC-ENET card if I just use a switch? If so...

Then I would plug the ethernet from the modem into the switch, the ehternet from another switch (that goes out to my network) into the switch, and then and ethernet cable from the swtich to the builtin ehthernet port on the router?

desai.jaideep Thu, 04/12/2007 - 19:42


Let me make myself clear.

You can plug the modem ethernet cable to a switch on port 1.Its ip is say Gw:

Then u plug the router's ethernet cable to the switch on port 2.

Then u plug your access switch to that switch on port 3.

Lets say that ur internal network is

Now on ur router ethernet do the following config:

int f0/0

no shut

int f0/0.1

encap dot1q 1 native

ip add

ip nat inside

int f0/0.2

encap dot1q 2

ipa dd

ip nat outside

ip nat inside source list 1 interface f0/0.2 overload

ip route

First try this.If it dosen't work for u, then there is no alternative other then going in for a WIC-1ENET card.




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