switchport mode trunk vs switchport trunk allowed vlan all

[Magesh Kumar]

If switchport mode trunk command allows multiple vlan on same interface, then what is the need of switchport trunk allowed vlan all command?

[balaji.bandi]

Switchport mode trunk - allows all the VLAN

switchport trunk allowed vlan XX ( means only allowed VLAN in the list) ALL means again all the VLANs

[Magesh Kumar]

Hi Balaji,

So you mean both are doing same function, Right?  Then why we need two separate command for same function?

With Regards,

Magesh Kumar G

[Martin L]

those options (add, remove, all, etc) are sort tricky a bit. I had same issues.

true, switchport mode trunk allows all vlans by default. but if u make some changes, vlans list of allowed vlan x is displayed,

so, switchport trunk allowed vlan all command can be use after any previous manual manipulation to go back quickly to default settings, aka allowing all vlans

Regards, ML
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[Captain HoOmi · Accepted solution]

You don't have to configure switchport trunk allowed vlan all. By default a trunk interface trust all VLANs, but if you have changed it manually to only allow specific VLAN(s) then you can change it back to all VLANs by this command