Resubnetting and Vlan Questions

[66catalina]

First let me preface this by saying that I am still in the process of becoming familiar with Cisco equipment, I am trying to consume as much information as I can but I still need some assistance from people that are smarter than I am to ensure I don't find myself in a situation that I can't get out of.

I am running out of addresses on our network, a network that I just inherited. I need to resubnet the devices in our network but I would like to keep traffic from our old ip addresses / subnets going while I do this.

I am assuming that I need to create two address on our vlans, is this correct?

My network currently looks like this:

Vlan 1: 10.10.10.X / 255.255.255.0

Vlan 3: 10.10.3.X / 255.255.255.0

Vlan 10: 10.0.0.X / 255.255.255.0

Vlan 45: 192.168.45.X / 255.255.255.0

Vlan 50: 192.168.50.X / 255.255.255.0

I am running a Cisco 4506 Switch that points to a Cisco PIX firewall.

I would like to jump to another subnet, but I don't want to be hunted down in the street by my fellow employees for taking down the network. So, if I can add the second subnet and ip address scheme to the vlan, how would I go about properly doing this? Or if I can't, would someone have a sugestion on what I can do to resubnet, but keep the existing network running in the mean time?

Also, would anyone have any ideas on a suitable cisco produced replacement for the small 3550 switches we have?

Thanks for the help.

[Jon Marshall]

Neil

Do you want to readdress or simply add another subnet ?

Why not just add a new subnet or number of subnets eg on your 4500 -

4500(config)# vlan 60

4500(config)# int vlan 60

4500(config--if)# ip address x.x.x.x

etc. for new vlans/subnets. 

Or have i misunderstood what you want to do.

Replacement for 3550s - 3560 or 3750 switches.

Jon

[66catalina]

Jon,

Thanks for reply, and the suggestion on the 3550 Replacements.

I guess what I am wanting to do is to keep evey thing plugged in as it is, but migrate our subnet to a newer subnet with more address space. I am probably wrong on this assumption, but aren't vlans tied to specific ports? Is that correct?

If I create a new vlan with the address I want, will I face routing problems with my existing vlans?

[Jon Marshall]

Neil

Vlans are tied to specific ports in the sense that ports are assigned to vlans.

I just wanted to ask do you really want to readdress everything, which you can do, or do you simply want to add more subnets/vlans ?

If you created new vlans you shouldn't have routing problems on the 4500. If there are any other bits of your network that need to know about the new vlans/subnets you would need to propogate those routes either using statics or using a dynamic routing protocol. Depends on what you do already.

As for a complete readdress you can either -

1) stick the vlans you have and use secondary addressing on the existing vlan interfaces and then move the clients in the vlan to that new address range

or

2) simply create the new vlan together with it's subnet and then move the clients into that vlan. You would still need to readdress but there would also be an additional step of changing the ports into the new vlan.

Jon

[66catalina]

Jon,

  Excellent, option one is exactly what I am wanting to do. We use DHCP for our addresses on the client machines. But, as I am sure you have experienced we still have printers and other pieces of network equipment that use static addesses. Moving the addresses of the DHCP clients is simple enough, but I don't want to cut off access to our devices with static addresses yet until I can move through them all and make the necessary changes.

So, how would I do this? Do I have to use telnet to set this up? Or can I use the Cisco Network Assistant? If I have to use telnet, what commands would I use?

[Jon Marshall · Accepted solution]

Neil

Firstly you need to confirm you can use secondary addressing on the L3 SVIs. I'm not a big fan of using them but if that is the way you want to go, login to the 4500 and you could simply create new vlan at L2, a new L3 vlan interface (see previous post for example config) and then try adding a secondary address to the SVI.

If that works then you should be okay. Sorry, i don't have a 4500 to test with.

Never used CNA, only CLI. If you telnet into the switch you should be able to use the commands i supplied previously.

Jon

[66catalina]

Great! Thanks for the help. I will give it a go and keep my fingers crossed. Wish me luck.