when we create vlan and port assign in vlan , we give a command switchport mode access.
switchport mode access
switchport access vlan 10
if we not give switchport mode access then what happend.
pls anyone clear to me ?.
1) "switchport mode access" in a layer 2 physical interface command and no matter it is 2950 or 3550 switch if you configure any physical interface and you want the interface to work as an access link and not a trunk link you will configure this command.
Even if you have layer 3 switch like 3550 you will create a vlan interface which is layer 3 interface for routing purpose but to bind any physical port to that layer 3 interface you need to have same vlan at layer 2 configured on some physical port so you use this command on layer 2 physical interface only.
2) If you want your link to work only as an access link and not a trunk link you have to use this command.
Now what happen if you do not use this command. Suppose you have another networkdevice which supports trunking connected to this interface but you want this interface to work only as an access link for single vlan what happens on cisco switch is like all the physical layer 2 interfaces are in dynamic desirable mode and they will try to form a trunk if the device conneted to this supports trunking and want to form a trunk. But if you configure "switchport mode access" command this interface will unconditionally form an access link working for only one vlan.
If you do not cofnigure this command it is not necessary that it will form a trunk it will TRY to form a trunk if the remote device is configured for trunking and supports trunking.