how to configure switchport connected to pbx for qos

[Athiqur Rahman]

Hi,

I  am trying to figure out how to setup quality  of service on my network.  At the moment i have computers connected to  the PC port of my IP phone  and the IP phone connected to the switch.

I want the PC to stay on the default native VLAN and the phone to go on the VLAN 10

I am using SNOM300 and SNOM360. I will configure the on the phone the VLAN ID and the priority.

From my research, there are two ways that I can go about this on the port that is connected to the phone I can

switchport voice vlan vlan-id

or

switchport voice vlan dot1p

and then I will have to execute the command

mls qos trust cos

my   question is which command do i use to configure the ports, and am I on   the right track? Also, this is how I configure the ports that the IP   phones are connected to, how do I configure the port that my Asterisk   PBX server is connected to?

Thanks

[Shashank Singh]

Hi,

Yes the configuration is right. But configure "mls qos" globally on the switch to enable qos. Follwinf is sample config:

switch(conf)# mls qos

switch(conf)#int gi0/1

switch(conf-int)# switchport mode access

switch(conf-int)# switchport access vlan 1

switch(conf-int)#switchport voice vlan 2

switch(conf-int)#mls qos trust cos

In case you have a cisco IP phone, following is the best practice:

switch(conf)#int gi0/1

switch(conf-int)# switchport mode access

switch(conf-int)# switchport access vlan 1

switch(conf-int)#switchport voice vlan 2

switch(conf-int)#auto qos voip trust

Cheers,

Shashank

Please rate if this helped answer your question

[Athiqur Rahman]

Thanks Sashshank. One more thing, we are able to to dictate that the prioity of the traffic coming into the switch from the phone. This is easily done on the phone by configuring the VLAN ID and priority. But is there a way of dictating the priority of the PC traffic coming into the switch? Can we say that any traffic that coming into the switchport from VLAN 1 should be a priorty of 3? I do not know  what priority will the switch will place on the packets received from the PC.

Thanks

[Shashank Singh · Accepted solution]

Hi Athiqur,

If the packets from the PC are already marked with a higher priority, you can configure " switchport priority extend trust" on the port which will just trust the priority of the PC packets. You can find out the marking of the PC packets through a wireshark capture.

If the PC traffic is not marked (mostly cos 0), you can configure, you can override the CoS value set by the PC attached to the Cisco IP phone and use the configured port priority instead. This feature is called port-based re-classification. The switchport priority extend cos <0-7> interface command is issued to achieve this.

Hope this helps,

Shashank

P.S. Please rate helpful post.

[Athiqur Rahman]

Sashshank, The big trick that has been missed here is that I am using Snom phones, not Cisco, so there is no CDP. From what I have researched, if there is no CDP then I can not do the " switchport voice vlan XXX " command. I will have use trunk ports instead? Could you give me some pointers on how this could be setup?

[sean_evershed]

I had a similar challenge to provide QoS for non Cisco phones on Cisco switches.

You need to find out what TCP and UDP port numbers the Snom phones use. Then write an ACL to mark the packets based on these port numbers.

Make sure that you capture all relavent ports. If you miss one or more then this will impact on voice quality.

[Athiqur Rahman]

The Snom300/360 I am using has the capablity to send out packets from the phone with tagged vlan and priority and leave the pc packets untagged. Does this make things easier to configure? Can i still use switchport voice vlan xx ?

[Shashank Singh · Accepted solution]

Hi Athiqur,

Yes in that case you can  use the switchport voice vlan command on the switch interface.

Cheers,

Shashank

P.S.Please rate helpful posts.

[Athiqur Rahman]

I am almost there, just on last thing.

How do i configure the port that my PBX is connected to? I am using a trixbox Asterisk PBX.

Do I just configure the port as an access port on the same VLAN as the ports that I can configured as switchport voice vlan xxx ?

[Shashank Singh]

Hi Athiqur,

"switchport access vlan #" is needed if you are planning to connect a PC to the IP phone and you wish to keep th PC data in a separate vlan.

If you do not intend to connect a PC to the phone, you can omit "switchport access vlan #" command.

Did this answer your question? If so, please mark it Answered!

Cheers,

Shashank

[bradfordjboyle]

Did you ever get a response on this?

I have a samsung system that's plugged into a cisco 2960.  I have set it has a "PC" or switchport mode access on vlan 100 to match my VoIP phones, however, I don't think it's prioritizing traffic.

I essentially want to take my PBX VoIP Server, plug it into my cisco 2960, and have the traffic tagged and prioritized as if it's a VoIP phone on VLAN 100.