# S-VLAN Subinterface with an Untagged C-VLAN ID Overview

In previous releases, you could configure an S-VLAN subinterface with a C-VLAN ID in the range 0–4095 or with the any (5001) keyword for the VLAN ID. The single- tagged frames with a valid S-VLAN ID or untagged frames were ignored for the subinterface. You can now configure an S-VLAN subinterface with a C-VLAN ID, the anyUntagged (5003) keyword , when the C-VLAN is configured inside S-VLAN as part of a pseudowire. As a result, both customer-tagged and untagged frames can be transported inside a prescribed S-VLAN-tag over a single pseudowire.

Observe the following guidelines when you configure an S-VLAN subinterface with any untagged VLAN, for which the C-VLAN ID 0 is reserved.

- Only Ethertype 0x8100 is supported on an S-VLAN subinterface that is configured with the anyUntagged C-VLAN ID. If you attempt to configure Ethertype 0x9100 and 0x8a88 on this S-VLAN subinterface, an error message is displayed.
- The default Ethertype of an S-VLAN subinterface that is configured with the anyUntagged C-VLAN id is set to 0x8100. For other VLAN subinterfaces, it is set to 0x9100.
- You cannot configure an S-VLAN subinterface with an S-VLAN ID value and the C-VLAN ID as anyUntagged if its Ethertype is 0x8100 and if any VLAN subinterface on the same major VLAN is configured with a VLAN ID value. Similarly, you cannot configure a VLAN subinterface with a VLAN ID value if any S-VLAN subinterface on the same major VLAN is configured with the same S-VLAN ID value, C-VLAN ID as anyUntagged, and Ethertype as 0x8100. If you attempt these procedures, an error message is displayed.
- If you attempt to configure the Ethertype as 0x8100 on an S-VLAN subinterface, which is configured with a valid S-VLAN ID value and C-VLAN ID as anyUntagged, and if any VLAN subinterface is previously configured with a VLAN ID value on the same major VLAN, an error message is displayed.

#### Related Documentation

- Examples: Configuring S-VLAN Subinterface with an Untagged C-VLAN ID
- svlan id