Telnet Trouble on 2950

Mr Big

Why is it that when I create VLAN's on my switch, I loose my telnet session? It completely boots me off and doesn't allow me to telnet back in? When I 'shut' the vlan, I am able to telnet, when I 'no shut' I can't. Why? I have an IP assigned to the switch, which is what I use to telnet with, but I don't see why the VLAN would not let me access my switch?

EdTheLad

Why are you doing a no shutdown on the vlan interface, the 2950 you have i'm sure is the cheaper model which can run an enhanced image but cannot perform layer 3 switching.Your switch will only support one vlan interface configured with an ip address for management what other reason can you have to enable a second vlan interface?.All you need to do is create a vlan and assign ports to it, this will not disconnect your telnet session.

forbesl

Cisco. com, anyone?

Click Here...cisco.com is your friend

Check out paragraph #4 under "Create VLANs and Ports"

Mr Big

I have 2 VLAN's that will trunk to a router. I have assigned an ip address to each VLAN and after assigning the IP isn't it required to do a 'no shutdown' ?

EdTheLad

Mr Big wrote:

I have 2 VLAN's that will trunk to a router. I have assigned an ip address to each VLAN and after assigning the IP isn't it required to do a 'no shutdown' ?

Didnt you pass Bcmsn a couple of weeks ago? Sorry, but i'm surprised you dont know how to setup a trunk.Why are you asigning IP addresses to the vlans? Are you trying to route between the vlans? If so you need layer 3 capablility on your switch, your switch will only support layer 2.The basic 2950 will only support one layer 3 vlan for management,if you enable a second the first will disable and you will lose management.

Mr Big

ed_the_lad wrote:

Mr Big wrote:

I have 2 VLAN's that will trunk to a router. I have assigned an ip address to each VLAN and after assigning the IP isn't it required to do a 'no shutdown' ?

Didnt you pass Bcmsn a couple of weeks ago? Sorry, but i'm surprised you dont know how to setup a trunk.Why are you asigning IP addresses to the vlans? Are you trying to route between the vlans? If so you need layer 3 capablility on your switch, your switch will only support layer 2.The basic 2950 will only support one layer 3 vlan for management,if you enable a second the first will disable and you will lose management.

No, I have not taken the BCMSN, nor am I CCNA certified, I am learning Cisco as I go through references and this web site HOPING no one will ridicule me for my inexperience or ignorance...

The Layer 3 capibility will be through a 2811 router..."Router on a Stick" topology.

So yes, I am trying to route between VLANs...the question is...when I set up these 2 VLAN's with IP's and perform a no shut so I can trunk to the FA0/1 interface on the router...I loose my telnet session...I just want to know why.

EdTheLad

Ah similar name to MrD, wasnt trying to ridicule as i said i was surprised, anyway mistaken identity, dont be so sensitive .
Anyway, you dont need to set an ip address on the switch,its working as a layer2 device.You create a vlan "vlan 2", and assign ports to this vlan which effectively groups ports into a logical bundle.This vlan is trunked to a router which will be setup with the appropriate vlan id.The router subinterface will also have an ip address.This ip address is used as the default gateway for host devices connected to the ports assigned to the vlan.Each vlan will represent a subnet but this subnet ip address isnt setup on the switch.All devices connected to the ports of a vlan should be on the same ip subnet as each other and the subinterface on the router that acts as the default gateway.

Mr Big

No harm done

Wierd...so what is the purpose of assigning an IP to a VLAN? I picked up a "CCNA Portable Command Guide" from the bookstore and it shows a step by step on configuring VLAN's...one of them was assigning an IP and a no shut. I would think this would be required to communicate to the trunk port on the router where I created subinterfaces on.

djmd

Mr Big wrote:

No harm done

Wierd...so what is the purpose of assigning an IP to a VLAN? I picked up a "CCNA Portable Command Guide" from the bookstore and it shows a step by step on configuring VLAN's...one of them was assigning an IP and a no shut. I would think this would be required to communicate to the trunk port on the router where I created subinterfaces on.

I thought that the sole purpose of assigning an IP to a vlan on a switch was for administrative purposes..... gives the switch an IP you can telnet to from the outside.

Webmaster

djmd wrote:

assigning an IP to a vlan on a switch was for administrative purposes..... gives the switch an IP you can telnet to from the outside.

Right, see step Configuring an IP address for the switch:

www.techexams.net/techlabs/ccna/lab-switch-basics.shtml

Mr Big

Ah...I see now, my mind is so IP address driven I didn't think of it before. I thought you needed an IP for the VLAN to communicate with the router, I didn't know the Router and Switch communicate through Vlan NUMBER. Thanks for clearing it up guys!

Danman32

It's easy to confuse switching with routing. I originally got confused on an exam question regarding a VLAN'd network, forgetting that switches don't route, even between multiple vlans on the same switch.

Because switches don't route, if you have VLAN 1 with IP 192.168.0.1, and you have VLAN 2 with IP 192.168.1.1, and you have a PC connected to a port assigned to VLAN 2, if you want to telnet to the switch without a router, you have to have an IP on the PC within subnet 192.168.1.x. If you originally had that port assigned to VLAN 1 with the PC's IP in the subnet for VLAN 1, then when you changed the port to VLAN 2, you no longer can reach the original management address.