I am having difficulty setting up the voice vlan on a 6248 switch. I've read the user guide, cli guide, config guide, a white paper and google but I'm still having an issue. I'm from a CISCO background so I'm not sure if it's a switch issue or an expectation issue on my part. The voice vlan is vlan 500, int 1/g37 has a Polycom IP Phone on it. On a CISCO 3750 switch the phone has been working as expected for months. We've just purchased our first Dell switches so I'm still getting used to the differences between CISCO and Dell.
The relevant swtich configuraiton I have is:
interface vlan 500
interface ethernet 1/g37
switchport voice detect auto
switchport mode general
lldp med confignotification
voice vlan 500
The main issue is with the operation of the phone and I have confirmed with by mirroring the port and watching the data with Wireshark.
1. The phone boots and sends some advertising packets
2. The phone get's a VLAN 500 dhcp address and boots as I would expect and as it does on the CISCO switch. Great!!
3. After about 30 seconds I see a DHCP release, a DHCP discover etc and the phone get a new IP address for our default VLAN 1 and reboots.
4. The phone boots and appears to work OK
5. I see packet flow and can make\receive calls bit it's with the default vlan address, not the vlan 500 address.
I can't understand why it would restart this way. Is it a phone issue or a switch config issue? This phone works fine as is on the CISCO switch on the voice VLAN. The phone does this restart every time - I must have done 40 odd restarts while trying to resolve this issue. Every time it's two restarts - the first one on vlan 500, the next on the default vlan.
As the phone is not using the voice vlan, I can only assume the traffic is not being prioritised as I would want. Do I need to not use vlan 500 and use voice vlan dot1q instead?
I've been on this for a week now - any pointer would be greatly appreciated,
Solved! Go to Solution.
I done some more traces concentrating on the ISDP (CPD) and LLDP packets. I can see the switch sending the LLDP multicast packets including the network policy. In the network policy I can the VLAN settings
When the phone sends its LLDP multicasts, I can also see the network policy and the PDU shows the network polciy is unknown. So it looks like the phone it not getting the LLDP MED policy from the switch.
Is there a compatibility issue perhaps between the LLDP MED on the switch and on the phone? Is there something else I need to do so the phone gets the policy
I provided this same answer in the Dell Techcenter Post that you provided on the same subject.
It looks like it may be an incompatibility with the phone and the switch. I did a search for LLDP thru this Polycom 450 IP phone User Guide and it has no mention of the feature.
You might give this example a try on the switch or use your example and leave the LLDP options out.
console(config-if-Gi1/0/10)#switchport mode general
console(config-if-Gi1/0/10)#voice vlan 25
Hope this helps,
Keep us updated if you can.
I did have a setup as you suggested but it didn't work.
The phones are working now. Turns out I had to turn LLDP off completely for the phone ports and ISDP works a treat.
Turns our what was happenning was:
1. The phone would get its initial config via ISDP and boot correctly on the voice vlan
2. The switch would advertise LLDP MED, the phone would update it's settings incorrectly (not get the VLAN info from the LLDP MED packet) and restart and VLAN 1 - hence the change in IP address
I have 3 phones successfully working of the switch now.