Virtual interfaces (ala eth0:1) on a Cisco 1720?

Factual Questions
1

I’m far more familiar with setting up Linux routers, and I know virtually no IOS, so I’d appreciate a little help here.

I’ve got to add a second subnet to a 1720. eth0… I mean, fastethernet0, is currently up and in production.

Can I set up a virtual interface in IOS with the same kind of notation I would for, say, Linux? Like, by naming it with a colon, eg fastethernet 0:1?

Here’s what I mean:

#config
#interface fastethernet 1:1
#ip address 2.2.2.1 255.255.255.0
#no shutdown
#^z

I’ve got a feeling that maybe I should use a / instead of a :, but like I said, I’m new to this. I just don’t want to touch anything until I’ve got a better idea of how I’m supposed to be doing this.

Thanks.

2

I’m no IOS guru by any stretch, but I’ll give you a bump in case you’re still hung up.

If you don’t really need another interface, but just need that interface to be in two (or more) networks, you can use more than one ip address command with “secondary” tacked on the end, like:

ip address 192.168.0.1 255.255.255.0
ip address 192.168.1.1 255.255.255.0 secondary

This has about the same effect as virtual interfaces in Linux. See here for more info.

If you are trying to do some fancy interface based routing or something, this may not be what you want. If that’s the case more details would be helpful.

3

If I remember correctly your example will work, but like you said use a / instead of a :. I am a CCNA, but haven’t used it in several years. You should be able to find an answer on the cisco website. I would look, but getting ready for work.

This is my second job where I was told I would be working with cisco equipment, but found out their idea of working with cisco equipment is turning it off and back on. If something else goes wrong we call someone else, but that is a rant for the pit.

-Otanx

4

Thanks folks. I eventually figured it out; it was indeed the ‘secondary’ argument that I needed.

For some reason, I also had to cycle the interface.

In Otanx’s example, the / is for slot/port notation for the higher-end boxes where you’ve got multiple ports.

Thanks again.