Cisco trunk port

[wilson2468]

As a lot of other people, I need to create a vlan trunk from 3com switch to Cisco 4503.

I have a subnet the switch is only routing to at the momment. I want to add the subnet on the switch as a VLAN and let the Vlan ip address be the defualt gatewway of the users on the 3Com.

At the moment , the users have a router on a stick that is passing traffic to the 4503 switch.

My questions are:

1. When creating the vlan on the cisco, can the only member of the vlan be the trunk port from the 3com?

I have done this and the vlan interface never comes up, it stays down/down.

2. If the only users at the other end of the trunk on the Cisco are in the same subnet (basically just uplinking the 3com to the Cisco), can't I just have the trunk carry the single VLAN?
Does that vlan have to be the native vlan?

3. If I creat a vlan 6 (example) and try to configure a single port as the trunk port, is there any danger of the switch traffing being taken down if everyone is in the default Vlan1?

 

[chipk]

Are you sure you need a trunk? Are you saying that you have a 3com switch with one, or multiple, vlans on it?

1. When creating vlans, the vlan will not change state to up until you put something in it (another host, port, etc.).

2. If you've only got one vlan on the 3com, just don't use a trunk at all, just make the uplink an access port.

3. I'm not sure I'm following what you're doing here. Trunks carry traffic from all vlans. If you have multiple trunks, be careful you're not creating a loop, and if you are, make sure you have your spanning-tree configured correctly. So, while creating another vlan won't take down another one, if you create multiple trunks, there could be unintended consequences - like spanning-tree shutting down a port.

 

[wilson2468]

We have 2 4502 switches and now they have multiple secondary interfaces in vlan 1

All port s are in vlan 1 so it is a flat network.

All other switches that uplink carry multiple subnets.

A couple of the switches only carry one subnet.

The goal is to have all uplinks have two trunks to the two different 4500 switches for redundancy.

So,

1. I need to create VLANs on the switches for each sunet to get away from flat network.

2. Make sure the users and servers can communicate once the vlans are created.

I am not sure of the configuration needed

 

[vipergg]

Just match the native vlans on each switch , if native is vlan 6 on the cisco make the 3com port native vlan 6 and set up the link as dot1q . When you create the layer3 SVI until you have a port in that vlan go active this layer 3 interface will not come active. On the 4500 you can put any port you want into that vlan to be part of that subnet , the nice advantage of a l2/3 switch. You can have as many vlans across the trunk as you want , when you intially create the trunk the 4500 will allow all vlans on the trunk and you would have to specifically disallow vlans if you want to .

 

[wilson2468]

Here is my config:

Created the additonal vlan (vlan2).
Set port one to be a member of both vlans.
On port one, vlanvl is untagged (native) and vlan2 is tagged (802.1Q).
All other vlan1 ports are untagged.
All other vlan2 ports are untagged.

Cisco 4503
Created the vlan and given it ip address.
Made it a trunk port.
Made vlan1 native vlan.
Allowed both vlans on the trunk.

It still will not trunk