12-08-2007 04:29 PM - edited 03-05-2019 07:53 PM
I have two 2950 switches. I am trying to set up a trunk over fa0/1 on both switches. There are no lights on the ports when I connect a cross-over cable. Any suggestions would help. I used the following commands on my first switch (Texas):
en
config t
int fa0/1
switchport mode trunk
speed 100
duplex full
-------------
switch two (Arkansas)
en
config t
int fa0/1
switchport mode dynamic
speed 100
duplex full
----------
Texas#show int fa0/1 switchport
Name: Fa0/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Protected: false
Voice VLAN: none (Inactive)
Appliance trust: none
-------------
Arkansas#show int fa0/1 switchport
Name: Fa0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Protected: false
Voice VLAN: none (Inactive)
Appliance trust: none
------------------------
Arkansas#sho int fa0/1 trunk
Port Mode Encapsulation Status Native vlan
Fa0/1 desirable 802.1q not-trunking 1
----------------
Texas#show int fa0/1 trunk
Port Mode Encapsulation Status Native vlan
Fa0/1 on 802.1q not-trunking 1
12-08-2007 05:00 PM
You can't have one side forced on (switchport mode trunk) and the other side "switchport mode dynamic desirable . Just make both sides " switchport mode dynamic desirable" which is the default setting anyway on these switches . If its truly a Xover cable and the ports are administratively enabled then you should get a link light otherwise check or replace the cable. These switches do not have mdix so you must use a xover .
12-09-2007 01:10 AM
Hi Glen
You can have "switchport mode trunk" on one side and "switchport mode dynamic desirable" on the other side and it will form a trunk because DTP will negotiate a trunk. If you look at the output of both interfaces and it says
Negotiation of Trunking: On
If you had
switchport mode trunk
switchport nonegotiate
then yes it would not work.
Jon
12-08-2007 08:46 PM
use a crossover cable, and set both ports to:
switchport mode trunk
that should work for you.
-brad
(please rate the post if this helps!)
12-09-2007 02:20 AM
Hi
could you check the both ports being "no shut".
As you can see on both ports you have "Operational Mode: down". This could be because of the cable or because one or both ports are in shutdown state.
12-09-2007 05:05 AM
John is correct about using "on" , though most cisco docs I have seen recomend using desirable - desirable on each end . I have seen problems where trunks are forced on and one end says its trunking and the trunk is not actually working .
12-09-2007 06:20 AM
glen,
yeah, i see the d/d config on a lot of cisco website configs as well.
where have you run into a problem? What type of switches? IOS? or CatOS? i'll lab it up and post the debugs.
i've been setting my 2950 trunks to "trunk" instead of desirable and havent had an issue. i know there used to be an issue (years ago) with doing trunk/trunk on older CatOS switches, but I haven't run into that in a long time.
-brad
(please rate the post if this helps!)
12-09-2007 10:38 AM
Thanks for everyone's response. It turns out the cable was the problem. It was not a Xcable as advertised.
Thanks
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: