Ethernet network to Cisco 1720

[webnetwiz]

Hey, everyone.
I've got a fast ethernet switched LAN, and what I want to do is actually attach a Cisco 1720 (which I got for free) to this network, and use only the ethernet port on 1720 to create another network. Here's the question; Can I use only the Ethernet interface to do routing between 2 networks?

 

[jeter]

You should if you run a routing protocol rip, igrp, eigrp etc etc.
You should be able to arp out and see the networks.

I bet Wybnormal could set you in the right direction on this !!!! Jeter@LasVegas.com
J.Fisher CCNA

 

[wybnormal]

Sure.. I have a 2514 setup in my lab right now that on E1, there are two different subnets.. 192.168.50.x and 192.1.1.x I used secondary IP for it work.. tho' you could use subinterfaces on the ethernet port to the same effect. I dont remember which version of IOS you need for the subinterfaces..

serial--------router-E0----192.168.50.1-- NT domain
|----192.1.1.1-- Sparc20--linix

Just remember that the rules of broadcast traffic applies here. And that secondary interfaces are a bit strange at times with routed protocols. The subinterface would be the preferred way but this was quick and dirty for my needs at the time.

Keep in mind that while neither network can "see" the other since they are different subnets, they both share the same wire so any traffic issues will effect both networks.

This is just one way to play this game.. a little imagination can go a long ways to having "fun" ;-)

MikeS

MikeS
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[webnetwiz]

But what if i need the router to route between those 2 networks on the same physical ethernet interface?

For example, i want an internal network 10.10.10.0 to talk to 192.168.12.0, because the latter one has access to the internet.

How would I go about that?

 

[wybnormal]

Since they are *connected* networks.. the router will automaticely route between them. No different then if you used a dual port ethernet like a 2514 or 2611, 2621 and had two networks connect via each port. When you do a "show ip route" both networks will come up as C for connected. If you wanted to get to a network that is NOT connected, then you need a route in place via static or routing protocol, that points the way.

Example printout from command:

C 204.137.43.96 is directly connected, Ethernet0

I would be more worried about the firewall or gateway to the internet not knowing what your IP range is or having it blocked.

Honestly tho', I can not think of too many reasons why you would want to do this on a production network.

MikeS

"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[webnetwiz]

I need to connect a few users with Cisco VPN 3000 Client, and they will VPN to another network. However, the admin over there want them on the "inside" of our firewall. Hey, he provided all the equipment. All I have to do is connect and configure that router.