Switchport: Data VLAN and Voice VLAN set the same. Issue?

[brandon02852]

Is there any issue with the config of this switchport?  I noticed that "switchport access vlan" and "switchport voice vlan" both point to the same vlan.  This port goes to an Avaya C-LAN card for VoIP

interface FastEthernet2/0/47

  switchport access vlan 241

  switchport mode access

  switchport voice vlan 241

  speed 100

  duplex full

  srr-queue bandwidth share 10 10 60 20

  priority-queue out

  mls qos trust dscp

  auto qos voip trust

  spanning-tree portfast

  spanning tree bpduguard enable

end

[Richard Burts]

There are some advantages that you get when there are separate vlans for voice and for data, such as being able to isolate the voice traffic from the bursty performance of the data traffic, or perhaps being able to establish different QOS behaviors for voice and for data. Obviously you lose these possibilities when the data vlan and voice vlan are the same. Whether that is important depends on things in your environment about which we have no visibility. As long as there is some device on the vlan which the data devices can recognize and use as their default gateway then data should work, and the voice data should be able to get to Avaya so I would think it is possible for this config to work.

HTH

Rick

[Joseph W. Doherty]

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Posting

I suspect the port would accept either tagged or untagged frames for VLAN 241.  As both frame kinds (tagged and untagged) go to the same VLAN, if the frames are untagged you lose L2 CoS (which shouldn't be a problem, as you trust DSCP), but if you don't need the VLAN tag you "waste" the space for it.

I'm unsure whether egress frames, on this port, would go out tagged or untagged.

I.e. assuming the devices works with this config, I don't see any major issues with it, other than the "huh?" reaction when looked at.

As Rick mentioned, you can run data and VoIP hosts on the same LAN, but there are advantages to run them on their own VLANs, one major one, is keeping data host broadcasts from hitting VoIP hosts.