6248P VOIP And Trunk Issue

Here are some points to keep in mind when enabling Voice VLAN.

• Voice VLAN is enabled on a per port basis. A port can participate in one Voice VLAN at a given instance of time.
• For the Voice VLAN to be operational on the port so that the connected IP phone can correctly communicate on the Voice VLAN:
  • Voice VLAN should be configured on the interface.
  • LLDP-MED needs to be operational on the port.
  • Configured Voice VLAN should be one of the active VLANs from the dot1q database.
  • The port should be authorized and link is active.
  • The port should not be part of a Guest VLAN or LAG interface.
• Voice VLAN becomes non-operational if the Voice VLAN ID is deleted from the dot1q database.

• Voice VLAN uses LLDP-MED to pass on the VLAN ID, 802.1p Priority, and DSCP values to the IP phone.
• The Voice VLAN operates in two modes – trusted mode and untrusted mode. The default mode is trusted mode.

• In untrusted mode, the CoS value is not trusted for 802.1p or 802.1q tagged traffic, and all untagged traffic is forwarded with CoS value of 0.
• In trusted mode, the CoS values of the 802.1p or 802.1q tagged traffic are forwarded based on the embedded priority info.
• All untagged traffic except the Voice VLAN traffic (if untagged) is associated to the default priority of the port.
• When Voice VLAN is enabled on a port, then the port is configured as an edge port (dot1s configuration) and when Voice VLAN is disabled, then the edge port remains configured.
• Voice VLAN can be enabled on a port only if it is configured as “General”.

And here is an example of what the port configuration would look like for the phone connection.

console(config)# interface ethernet 1/g10

console(config-if)# spanning-tree portfast

console(config-if)# switchport mode general

console(config-if)# switchport general pvid 1

console(config-if)# switchport general allowed vlan add 1

console(config-if)# switchport general allowed vlan add 101 tagged

console(config-if)# lldp transmit-mgmt

console(config-if)# lldp notification

console(config-if)# lldp med

console(config-if)# lldp med confignotification

console(config-if)# lldp med transmit-tlv inventory

console(config-if)# voice vlan 101

console(config-if)# voice vlan auth disable

For your switch to switch connection the configuration would be:

console(config)# interface ethernet 1/e47

console(config-if)# switchport mode trunk

console(config-if)# switchport trunk allowed vlan add 101

If that is not allowing traffic to traverse the connection, you can try General mode.

console(config)# interface ethernet 1/e7

console(config-if)# switchport mode general

console(config-if)# switchport general allowed vlan add 101 tagged

Let us know if this helps out.

That's awesome - I am not in the office today but back in on Tuesday so will attempt the change then. and will let you know. many thanks for giving the whole config!!

Hi,  I tested this today and it partly worked.  However the Cisco 800 is managed by the phone company and does give a DHCP range of 172.20.132.x when plugged into the old switch however when plugging into the dell switch i pickup my dhcp range for the computers which the server is dishing out.

Yes that's correct. Model phone is Cisco SPA504G.  I have spoken to the hosted phone provider and they don't support this with Dell switches so I may have to leave it!

Hi,

That worked perfectly - thanks very much for all your help and quick assistance!!!

Good to hear, thanks for the update.