configure vlan

[MinhVu07669]

What is the difference between "switchport trunk allowed" and "switchport trunk native" commands?

[balaji.bandi · Accepted solution]

high level :

switchport trunk native - Native VLAN is an 802.1Q concept: frames belonging to native VLAN are sent untagged. (if you do not mention default is VLAN1)

switchport trunk allowed XX ( this prevents other VLAN passing over trunk) - so it will be Limited to that VLANs only.

hope this makes sense?

[pmckenzie]

Good question

the command "switchport trunk allowed" indicates to the switch which VLANS are allowed to be received, transmitted and also which VLANs can be blocked. (all VLANs allowed by default)

eg VLANS 1-10 and 12 are blocked by first statement, second statement allows VLAN 7

switchport trunk allowed vlan remove 1-10,12

switchport trunk allowed vlan add 7

the command "switchport trunk native" simply means that the switch will not tag that VLAN. All VLANs are still allowed but will be tagged using 802.1Q protocol. Each switch upon receipt of the Frame will unpack it, look at tag and be able to categorize which VLAN that Frame belongs to. If Frame doesn't have tag Switch will categorize it as Native. (both connected switches need to have same native VLAN defined.