Trunking not working

[aelharam]

Hi All,

I am setting up two 2960 cisco switches, set up two vlans (Vlan 1 (default)  Vlan 5). i configured gi1/0/1 to be a trunk port for both switches using :

en

conf t

int gi1/0/1 

switchport mode trunk

switchport trunk allowed vlan 1-1000

and i have done this on both switches however the trunk port is not working. i used a crossover cable in port 1 on both switches. when i do 

show int trunk

i dont get anything returned.

Can you please advice.

Many Thanks

Abdo

[Mark Malone]

Hi

you don't need a crossover the switches support mdix so a straight through will do fine 

are the vlans added at layer 2 on each switch in the ... show vlan and both trunk ports are up/up each side

try the straight through instead see if it makes a diff your config is fine once the vlans are in place at layer 2

[aelharam]

Thanks for the fast reply, and yes they are both layer 2 vlans, however can you clarifiy what you mean by "both trunk ports are up/up each side"

[Mark Malone]

Hi

that the physical interface are showing up/up on each switch , each port that's set as a trunk  , try a straight through it will prob come up  

show ip int brief
GigabitEthernet1/0/16  unassigned      YES unset  up                    up

[aelharam]

This is the results i get after typing sh ip int br:

GigabitEthernet1/0/1  unassigned      YES unset  administratively down                 down

[Mark Malone]

ok that the issue port is manually down , needs to be brought up , make sure both sides are up/up then , run same command again after the no shut on each interface , then show int trunk

(conf t)

int g1/0/1

no shut

[aelharam]

Ive run the above commands and now when i do:

sh ip int br

im getting:

GigabitEthernet1/0/1  unassigned      YES unset   down                 down

[Mark Malone]

so when its down /down and not up/down , that means you have a physical layer 1 issue which is either port is shut , the cable is faulty or its not connected at other end , unlikely the port is faulty

make sure both sides are not admin like that last output , the far end where g1/0/1 other end of the trunk is not admin down either

change the cable to straight through standard cat5 /6 cable

You wont see ay trunk info until the ports are up/up each side at interface

[aelharam]

i dont think it is a port issue because when i run 

conf t 

int gi1/0/1 

switchport mode access

switchport access vlan 5

ex

it works. However when i change it to a trunk port i does not work.

[Mark Malone]

physical switch port does not care when its access or set as trunk , it should come up physically either way once the cable is connected between the 2 switches

from both switches where the cable is connected between the ports and its set as trunk

can you post please the

sh run int x/x

and show int x/x

This will allow us to see if there something else causing it  

[aelharam]

Ive attached a screenshot, this is one of the switches

[Julio E. Moisa]

Hi

A switchport cannot be as trunk or access mode at the same time (it will not affect the port status), but as Mark mentioned you should replace the cable. 

[Mark Malone · Accepted solution]

ok its configured wrong and has gone into err-disabled mode as per the interface status

the reason is you set portfast which is only for access ports , when the switch bpdu came in it went error the port to stop a loop as it thought it was access port  , please remove everything but the below and you will need to bounce the port again , shut , then no shut each port , make sure each side just has the below  

int g1/0/1

switchport mode trunk

switchport trunk allowed vlan 1-1000

### A quick way to do it is ....(conft)default int g1/01

That will set it back to original no config just for the port rather than having to type no for each line

[aelharam]

Thank you very much, that has solved my issue.

[Mark Malone]

great , glad we could help