Trunking help

[matttate1]

Hello everyone,

I have a problem getting a trunk port working between a 3750 stack and a 4507 chassis. The 4507 will form my new core but I am trying to configure it along side before testing and rollout but can't get it talking on my management VLAN. I have a VLAN setup as my management network on the 3750 but cannot get it to ping the new 4507, an excerpt from my config is below

interface Vlan21

description Native

ip address 10.50.0.129 255.255.255.128

end

I have also setup the 4507 with VLAN 21

interface Vlan21

ip address 10.50.0.131 255.255.255.128

no ip route-cache

end

VTP has been set to server on the 3750 and client on the 4507 but I still cannot ping the interfaces from each device

Port Config on the 3750

interface GigabitEthernet2/0/24

description Server Core LINK

switchport trunk encapsulation dot1q

switchport trunk native vlan 21

switchport mode trunk

end

Port Config on the 4507

interface GigabitEthernet1/48

switchport trunk native vlan 21

switchport mode trunk

end

Any help would be apprecaited

Thanks

Matt

[Parvesh Paliwal]

Hi Hardi,

This has nothing to do with routing - they are on same vlan and same subnet.

The only lack is they are missing L2 connectivity.

Dear Matt,

Can you check if the switches have CDP enabled, is there some mac-address being cached (sho mac-address) ?

[Hardi Ahmed]

Hi parvesh,

I think he has more than 2 vlans in each  devie, so I suggested to configure dynamic routing.

Hi Matt,

here some new steps:

1- apply the trunk configuration on a differet interface and from  both ends.

2- enable CDP on both devices.

3- use a different media UTP cable in this interconnection.

[matttate1]

Ok as suggested by devils advocate I have started again with the trunk config...

I have now also changed interfaces on both the 3750 and the 4507

CDP is enabled on both by going to config t - cdp run

I have also changed the cable

I am still getting nothing in CDP neighbours and cannot ping each side of the trunk.

I have logged a call with Cisco TAC via my SmartNet contract as well now.

This config should have been really simple!

[glen.grant]

   If you don't have cdp neighbors then that's a physical issue unless cdp has been turned off .  If you want  to try again on each side try.   If it doesn't come up check logs for error .  Before anything else plug the devices together and you could just make the ports access ports in vlan 21 and it should ping across .  Both sides must show connected and you should see cdp . If not your you might have an issue with your cables .

vtp domain XXXX   (must match)

interface x/x

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan  21

switchport mode dynamic desirable

In this case native vlan is 1 because none is specified.

[Parvesh Paliwal]

Even in case there are multiple vlans, it should work if both trunk interfaces carry the vlans.

Matti, share the complete config and interestingly the output from - sho mac-address.

[devils_advocate]

Agreed, we need to see complete configs as something doesnt add up

[Hardi Ahmed]

Hi Matt,

did you checked the local time on both siwtches? should in the same configuration.

[matttate1]

I wish I could post the configs but it is a secure environment so I can't. I have changed the physical cable, ports in both devices and still can't see anything on CDP neighbors which suggests that something else is going on! I will see what the TAC say but will post any feedback I get from them here in case it helps anyone else

[Hardi Ahmed]

Hi Matt,

try to connect the two switches through two access ports and from the two end, have a check if you have any traffic between the connected ports.

the connected ports and from the two devices have to assign to the same vlan.

[Panos Bouras]

Hi,

can you check all your security configuration like running services, access lists, port security etc. and make sure that they don't affect the communications.

If you can backup your running configurations and just for a test reset to factory default and then try to connect both switches.

[Joshua Senft]

I have to agree with Hardi that something is off here. Your original post showed your port configurations with the 'switchport trunk native vlan 21' command present however the ouput you posted for 'show int trunk' showed VLAN 1 as the native.

Try setting both switches to VTP transparent mode and see what happens.