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Solved
Voice VLAN command - LLDP seems to stop working
I have a strange issue with the voice vlan command that I'm trying to isolate between our switches and Shoretel phones, but it seems there's no debug options for LLDP on this switch.
We use the...
FWIW this issue seems to be fixed. Originally the config was
interface 1/0/1
voice vlan 10
switchport mode access
switchport access vlan 20
But the switch would randomly stop passing the tagged VLAN traffic. I changed the config to:
interface 1/0/1
voice vlan 10
switchport mode trunk
switchport trunk native vlan 20
switchport trunk allowed vlan 10,20
I haven't had a single DHCP failure/VLAN tag drop since moving to this config.
This behavior seems to only occur on the M4300 series - the M4100 actually rejects switchport mode access as a valid option when using voice VLAN (I have those access ports configured in general mode but I'll be updating them later for the sake of consistency). Maybe it would be nice in future updates to prompt users to use a trunk config when enabling voice VLAN on switchports so they don't spend their time flailing about like I did (this problem lasted for like, seven or eight months!). :)
To be clear, it wasn't LLDP failing to maintain the voice VLAN tag, it was the switch refusing to pass tagged traffic and the phone dropping the VLAN tag after DHCP repeatedly failed (which is normal Mitel/Shoretel behavior).
If anyone else googles this problem hopefully they find this post. :) :womanvery-happy:
To follow up on this, the issue is happening again. It's actually happening on two separate switches.
The normal sequence of events I expect to happen:
Phone receives POE, and boots:
<13> Mar 1 10:36:07 M4300-52-POE+ TRAPMGR[PoE Req]: traputil.c(795) 403575 %% PoE: 3/0/20 power down
<13> Mar 1 10:36:10 M4300-52-POE+ TRAPMGR[PoE Req]: traputil.c(795) 403577 %% PoE: 3/0/20 power up
Link comes up:
<13> Mar 1 10:41:17 M4300-52-POE+ TRAPMGR[trapTask]: traputil.c(753) 403660 %% Link Down: 3/0/20
<13> Mar 1 10:41:22 M4300-52-POE+ TRAPMGR[trapTask]: traputil.c(753) 403665 %% Link Up: 3/0/20
<13> Mar 1 10:41:42 M4300-52-POE+ TRAPMGR[lldpTask]: traputil.c(795) 403671 %% LLDP-MED Topology Change Detected: ChassisIDSubtype: 5, ChassisID: 0.0.0.0, DeviceClass: 3, Interface: 3/0/20
<13> Mar 1 10:42:15 M4300-52-POE+ TRAPMGR[lldpTask]: traputil.c(795) 403671 %% LLDP-MED Topology Change Detected: ChassisIDSubtype: 5, ChassisID: [Phone receives IP from DHCP], DeviceClass: 3, Interface: 3/0/20
And I can see the output:
(M4300-52G-POE+) #show lldp remote-device all | include 3/0/20
3/0/20 283 [Phone IP] 00:10:49:xx:xx:xx Serial Number: ...
That isn't happening in this case. The POE and link come up fine, but no LLDP information is exchanged between the phone and the switch. The fact that a reboot fixes this, and that this only happens with our M4300s, leads me to think it might be an issue with a) the switch firmware itself, or b) stacking the switches somehow contributes to this issue (I have yet to see the issue manifest in a non-stacked switch, like in our lab).
If there are any other log entries or outputs I can pull to help narrow down the issue, I'd appreciate it. I am running out of ideas and, quite frankly, this is a pretty disruptive problem to have.
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