native vlan

[carl_townshend]

Hi all, can anyone tell me why we have native vlans, and what we would use them for

[Martin Parry]

Hi Carl

In a dot1q environment, all traffic that is not tagged with a vlan id is placed in the native vlan. for instance things like cdp, and network control traffic.

[royalblues]

The native VLAN is a term used with interfaces that are configured as VLAN trunks.

When a switch port is configured as a trunk, it tags frames with the appropriate VLAN number.

Frames from all VLANs are carried across the trunk link containing the 802.1Q or ISL tag, except for frames belonging to native vlan.

By default, frames from vlan1 belong to native VLAN, and are carried across the trunk untagged.

Have a look at this link

http://krypton.fhda.edu/~mmurphy/cnet-54c/references/NativeVLAN-CCNA3.pdf

HTH, rate if it does

Narayan

[smothuku]

Hi carl ,

Significance of Native VLAN

When you use an IEEE 802.1Q trunk port, all frames are tagged except those on the VLAN configured as the "native VLAN" for the port. Frames on the native VLAN are always transmitted untagged and are normally received untagged. Therefore, when an AP is connected to the switchport, the native VLAN configured on the AP must match the native VLAN configured on the switchport.

Note: If there is a mismatch in the native VLANs, the frames are dropped.

check out below link

http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_example09186a00801d0815.shtml

Thanks,

Satish

[carl_townshend]

is it possible to get the switch to drop untagged frames ?