I have trunk port between two swithes, bot are in same vtp domain, and I cannot put switchport trunk allowed vlan command on port. After commande there is no this command in config, and when I look at port with sh int x/x trunk, also nothing changed
don't add the vlan, allow it only if it is the 1st one and only one on the trunk. after that u can use the "add "
Switch(config-if)#switchport trunk allowed vlan 99