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Vlan advice

nero64
Occasional Contributor

Vlan advice

Sorry this is long but please read.

I just started configuring switches last week in place of my colleague who is ill in hospital and won't be back to early Jan. Anyway I'm learning quickly. Which is good because I'm studying for my CCNA.

I was given the task of setting up a Vlan on a 3550 switch for our training room. The thing was I had to pull the existing 2948G switch out and use its settings and put them on the new 3550. The old one used a Bridge group but I figured that I have its IP so I could work it out.

Anyway just to make sure I got the config from another 3550 switch, configured by my colleague, in the room which used Vlan 34. I noticed that all the ports were configured to use Vlan 1 which is the default but it uses the correct IP for Vlan 34, so you have the following:

Vlan 1 (10.96.34.135/25) --> all port interfaces. ie 34 is for Vlan 34 on our network.

So with the new 3550 I said ok I will just leave all the ports on the deafult Vlan 1 and assign it the IP 10.96.32.6/25 which is what the 2948G Bridge group 32 used.

Ok everything seemed fine. But I began thinking that both shouldn't be assigned to Vlan 1 so i tried to rechange the IP on vlan 1 for this second 3550 switch and create a Vlan 32 and assign the IP from above. I couldn't do it because it kept saying 10.96.32.0 is already assigned to vlan 1 even though I had changed the IP on Vlan 1 to somehing else.

Anyway in the end I just left it all to Vlan 1 and everything seems ok, but how can I remove the IP on Vlan 1 and set it up on the new Vlan 32. Or is ok to leave it on the defaults for both switches. I'm thinking that it doesn't matter because the IP's are different and Vlan 1 is just used locally by the switch not globally. Please someone give me some advice?

3 REPLIES
Thomas Bianco
Honored Contributor

Re: Vlan advice

you might want to dump the whole config to a file, read it through for references to VLAN 1 and change them to VLAN 34 (excepting the default entries), reload it and reboot.

the configurational interface isn't always complete, and sometimes a full flush are reload is best, esp when changing something like whole vlan ranges.

really, the ips for VLANs are just the switch interfaces on that VLAN, not really needed unless you need to configure the switch from that VLAN. some port (probably uplink, or router), or if those switches are layer 3 capible, a routing interface, needs to be on both vlans
There have been Innumerable people who have helped me. Of course, I've managed to piss most of them off.
Jeff Brown_15
Frequent Advisor

Re: Vlan advice

The problem is that the switch in question is a layer 3 switch. If you ran a "show ip route" you will see that 10.96.32.0 route is directly conected to VLAN1.

You need to go into "interface vlan 1" and set "no ip address 10.96.32.6 255.255.255.0".

After that you can set the IP on VLAN 32.
Thomas Bianco
Honored Contributor

Re: Vlan advice

jeff brown nailed what i danced around (but eventually missed).

Ps. this is a zero point post
There have been Innumerable people who have helped me. Of course, I've managed to piss most of them off.