QOS with 802.1p

[Christoph Zach]

Hello

We have two locations, connected via a wireless RF bridge.
At location A we have an 5308XL Switch.
At location B we have an 2626 Switch.
On both locations we have defined two seperate VLANS for VOIP, at location A VLANID 16, and at location B VLANID 35.
The interconection between these Switches is in VLAN1, and both Ports are tagged members of vlan1
The ports where the packet enters the switch, where the ip phones are connected to the Switch are untagged members of vlan16 or vlan 35.

I have set up QOS like this
site A: vlan 16 qos priority 5
site B: vlan 35 qos priority 5

When a packet enteres the Switch at site A it will be tagged with vlan ID 16, then enters the vlan 1, traffel to site B via the wireless bridge and enters vlan 35.

My Question: is the 802.1p priority preserved when the packet travels through different vlans or not.

Or must we set up qos between different vlans with TOS DSCP ?

[Matt Hobbs]

I'm fairly certain that the 802.1p priority is preserved when travelling through different VLANs as long as the switch to switch links are all tagged. I'll double check this tomorrow just to make sure.

Is there a reason though that you want each site to have it's own voice VLAN? If possible I would use just the one voice VLAN, keeping it tagged between the two sites. I would do the same for any other VLANs on the 2626 and let the 5300 do the routing (if the bandwidth between the 2 is sufficient). At minimum though I would seriously consider not routing that voice VLAN.

This will help avoid any routing issues that may occur. The 2626 routing performance can suffer if the host route table limit of 128 is reached - http://www.hp.com/rnd/support/faqs/2650_6108.htm#question181 - after which it will start routing in software and you will start getting performance complaints.

[Christoph Zach]

hello matt

Because we have to locations, 700 meters distance, and these two locations ar connected via a wireless bridge with 24 MBit Bandwith.

When i have 1 Vlan for this 2 Locations, Broadcasts goes through the relative slow Link.
This wireless link will be used for voip and data traffic

We will have a maximum of 20 Routing entries, never will reach the maximum of 128 routing entries

another questions:
must the ports where the voip telefons are connected to the switch are tagged members of the voip Vlan or is it ok when this ports ar e untagged members of the voip VLan.


bye, ch

[Matt Hobbs]

must the ports where the voip telefons are connected to the switch are tagged members of the voip Vlan or is it ok when this ports ar e untagged members of the voip VLan.

For the ports where the VOIP phones are connected, it's okay to leave them untagged as your VLAN QoS Priority setting will insert the tag for you.

For VOIP phones that have a built in switch port for a PC, in that case you would want the voice VLAN tagged, and the data VLAN untagged for the PC.

[Matt Hobbs]

Hi Christoph,

I've confirmed that the 802.1p priority is preserved when the packet travels through to a different VLAN as long as the switch to switch links ports are tagged.

Matt

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