Vlans misses in switch trunk port

[shivathapa]

I see in some cisco switches that vlans in trunk port misses frequently.what must be the reason behind this??

[greg.washburn]

Can you provide more information?

For example:

If you are referring to something like:

show run int fa 0/1 giving the following output:

interface fastethernet 0/1

switchport mode trunk

vs

interface fastethernet 0/1

switchport mode trunk

switchport trunk allowed vlan 1,25,200

or are you referring to something like show vtp status or show spanning-tree output.

[greg.washburn]

Can you provide more information?

For example:

If you are referring to something like:

show run int fa 0/1 giving the following output:

interface fastethernet 0/1

switchport mode trunk

vs

interface fastethernet 0/1

switchport mode trunk

switchport trunk allowed vlan 1,25,200

or are you referring to something like show vtp status or show spanning-tree output.

[shivathapa]

Thanx for ur reply,

i have tried sh run int faX/y and also tried sh int fax/y switchport

After i manually add vlan,then it starts to work.Its happening to some switch trunk port only .

its cisco 2950 24 port switch.