Switch Trunking Issue

[ScottishSmile]

I have one switch in place (Cisco Catalyst 3960-CX 16 port.) and I want to connect another switch to it via a trunk port. The second switch is an older catalyst 3960 24 port.

My Network uses VTP, and the trunk link has the native vlan set as 20.

I did the usual commands on both switch ports:

int ......

switchport mode trunk

switchport trunk allowed vlan all

switchport trunk encapulation dot1q

switchport trunk native vlan 20

no shut

Both switches are joined to VTP domain as a client

I found layer 2 to be working.

using "show interface ... trunk"   -  Dot1q and native vlan24 are both on the trunks. All vlans are allowed.

You can do "show CDP neighbor" and see each other.

Spanning tree shows a root port pointing to the active 3960-cx switch.

Layer 3 isn't working on the new switch. No dhcp for vlan 20, doesn't work if I set a static IP either.

Can't ping between the switches - I get a protocol not running error.

Also VTP isn't working. Revision number doesn't change no new vlans added.

Never seen this before. Anyone got any ideas?

[Leo Laohoo]

Check the VLAN database for the presence of VLAN 20.

[ScottishSmile]

I have created vlan 20 using the vlan database and configured it in interface mode.

It does NOT show up when you do "show vlan" .

#vlan database

#(database) vlan 20

(config)# int vlan 20

(config)# ip address dhcp

I also think this could be the issue. It's odd that I can see the native vlan 20 in the "show interfaces .... trunk" command and I can find the other switch by cdp.

[Leo Laohoo]

sh vlan-switch

[ScottishSmile]

Thanks for the help mate, I managed to figure out what SOME of the issues were:

1) Once VTP is enabled the catalyst switch needs you to move the vtp to server mode before making new vlans and then entering apply in vlan database. Best to move to a test vtp domain when doing this as your revision number increases.

switch(config)# vtp domain TEST4567

switch(config)# vtp mode server

switch# vlan database

switch(vlan)# vlan 20

switch(vlan20)# apply

switch(config)# vtp mode client

switch(config)# vtp domain [original domain]