10-25-2009 11:57 AM - edited 03-06-2019 08:17 AM
Hi,
It may sound very basic. But most of Engineers in my surrounding unable to clarify this. I tried in real switches also but not able to find the reason
Trunk and access VLANs in the same Port
INT FA 0/0
SWITCH MODE TRUNK
SWITCH ACCESS VLAN 100
SWITCH TRUNK ENCAPSULATION 802.1Q
Here what is the meaning and purose of giving SWITCH ACCESS VLAN 100 command in the TRUNK link. I think it is no way going to limit the number to allowed VLANs etc.
Please share your ideas.
sairam
10-25-2009 12:28 PM
Switchport access vlan 100 is doing nothing in that config and does not need to be there . The state of the port is determined by the switchport mode trunk command . If you wanted it as access then you would use switchport mode access. You can also use switchport mode dynamic desirable which means if the far end is auto or desirable it will become a trunk if it is not then it would be a access port , the vlan determined by the switchport access vlan Xx " command . In the command that you show all vlans are allowed on the trunk . to restrict the vlans across the trunk you need "switchport trunk allowed vlan xx,xx,xx , where xx is the vlans you want across the trunk.
10-25-2009 04:15 PM
Sairam,
Agree with Glen 100%.
Another misconception is assuming Vlan 100 serves are the native vlan on the command above. On the trunking mode, the native vlan is declared with the 'switchport trunk native vlan' command and based on the output above, the native vlan is '1'.
Regards
Edison.
10-26-2009 03:27 PM
Looks like a bit of old config that hasn't been removed. It's serving no purpose.
10-27-2009 05:53 PM
Sairam,
When you configure a switchport as trunk,it can carry a tagged packet and untagged packet simultaneously.If the switch receives a untagged packet on trunk port,it forwards it to native or VLAN 1 of the switch. If you want to change this to Vlan 100,then use command #switchport trunk native vlan 100.
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