Trunking commands on Catalyst 2950 ver 12.1

[networker99]

I have a Cisco 2950 with a trunk link which reads as follows.

interface FastEthernet0/4

switchport mode trunk

switchport nonegotiate

speed 100

duplex full

I have 2 questions, firstly why does the encapsulation method not show? and secondly when I try to place the same configuration on a 3560 I have to specify the encapsulation method before it will let me configure the port as a trunk.. and when I show the running config is shows encapsulation method in the running config unlike the 2950.. why the difference? and what am I missing? and is there any functionality difference?

Thanks in Advance!

[Leo Laohoo]

firstly why does the encapsulation method not show?

Because the 2950 (along with the 2940, 2955 and 2960) support only Dot1Q.

3560 I have to specify the encapsulation method before it will let me configure the port as a trunk

3560 and the rest of the 3XX0 series switches will support both Dot1Q and ISL.

In both switches, enter the command "sh interface capabilities" and look under "Trunk encap. type:".

[networker99]

Thanks, one last question.. why does the native VLAN not show under the running config on

the 2950?

[Reza Sharifi]

That is because vlan 1 is the default vlan.  If you change the native vlan 1 to a different number, it will then show up in the config

have  a look at below config from a 2950 switch  I have changed vlan 1 to native 20

Current configuration : 129 bytes
!
interface FastEthernet0/25
switchport trunk native vlan 20
switchport mode trunk
no ip address
spanning-tree portfast
end

Management-Switch(config-if)#

HTH

Reza

[jughosh]

Adding to the above, the best commands to view native Vlan will be "show interface interface-number swithcport" and "show interfaces trunk".......