2940, trunking

[Rutger Blom]

Hello,

We want to set up a trunk between a 2950 and a 2940 switch, but we are having problems getting it to work.

The VLAN information (database) is just not coming down to the 2940 switch. Native VLAN number is the same on both switches. Native VLAN is up on both switches. We tried to set the vtp mode to client on the 2940 but it keeps going back to transparant mode. Is this something new? Should vtp be transpararant on both sides?

Kind regards,

Rutger

[lgijssel]

Most probable cause is that the switch does not accept any change to vtp config (i.e. changing vtp domain) when in transparent mode.

Could also be that you omitted to terminate vtp configuration with "exit". (used ctrl-Z instead?)

Set the switch to vtp server first, then change the vtp domain and properly exit vtp config mode (with "exit"). Beware of the revision nr to prevent accidental erase of the 2950 vlan database.

Regards,

Leo

[Rutger Blom]

Changing to server doesn't work on the 2940 neither. It only wants to run in transparent mode.

When configuring vtp we do it via:

config t

vtp domain XXXX

vtp mode client/server

end

wr

[lgijssel]

The order in which the commands are given matters here. Rather try:

config t

vtp mode client/server

vtp domain XXXX

end

OR:

switch#vlan database

vtp mode client/server

vtp domain XXXX

exit

Leo

[pvezina]

The 2940 switch supports only 4 802.1Q VLANs and 4 Spanning-Tree instances. If the VTP information it receives contains more than 4 VLANs, it then switches to VTP transparent because of the mismatch. We had the same problem here. The only way to make it work is to leave the switch in VTP transparent, and manually define the VLANs you want to use on your switch (max of 4). Hope this helps.

[Rutger Blom]

But when defining more VLANs manually they can not be up at the same time. Only one VLAN can be up and the rest changes to administratively down.

I think if what you tell me is true this is a very strange switch Cisco brought onto the market.

Rutger

[ankurbhasin]

HI Rbml,

I think you can try Extended-Range VLAN

Check this link for more details

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat2940/12122ea2/2940scg/swvlan.htm#wp1394908

Also make sure you have the trunk properly configured between the 2 switches and then only all the vlans will be active. For extended vlans your switch should be in VTP transparent mode.

Regards,

Ankur

[pvezina]

You have to check between two different things here. VLAN interfaces are only a way to manage the switch. It is true that there can only be one VLAN interface "up" at any time. But the VLANs on the switch are a totally different thing, you define them using the "vlan database" exec command. Those VLANs are used to put ports in different broadcast domains. The limitation here is 4 VLANs at the same time for the 2940 switch. Hope this helps you.

[Rutger Blom]

Allright. So I should just create the "local" VLANs with the same id as the ones that would come via VTP and things should work?

We use one VLAN interface with an IP adress for management. This shouldn't be a problem?

Rutger