IP phones and Catalyst 3750

[getamessay]

Dear All,

I have one-way audio issues with IP phones 7962G connected to a catalyst 3750. The problem is calling between two IP phones one the same switch and same VLAN. 

The scaniors are as follows:

1. Both IP phones on the same switch and same VLAN. The called phone rings but there is only one-way audio.

2. Both IP phones on the same switch but different VLANs. No problem at all.

3. Each IP phone on different swicthes but on the same VLAN. No problem at all.

I have also done wireshark capture and see ARP request sent by one of the phones but unanswered.

Catalyst 3750

IOs version:  3750-ipbasek9-mz.122-55.SE3.bin

Port Settings:

interface FastEthernet1/0/8

switchport mode access

switchport voice vlan 81

ip arp inspection limit rate 100

mls qos trust device cisco-phone

spanning-tree portfast

spanning-tree bpduguard enable

spanning-tree guard root

service-policy input IPPHONE+PC

ip verify source port-security

Thank you in advance.

[paolo bevilacqua]

Remove "msl qos", service-policy, arp inspectio, and ip verify commands and try again.

[getamessay]

Dear Paolo,

I have tried what you suggested with plain default config and I still have the issue. Strangly it sometimes works even with the config I posted. I think the problem could be related to ARP bordcast. Either the switch is not sending ARP brodcast or the called phone is not responding for the ARP request.

Thanks

[keanej · Accepted solution]

I run loads of phones on this type of switch, without problem.

Try this config just for troubleshooting.

NB - you are using vlan 1 for your datatraffic - is that intentional ??

conf t

!

default int fast 1/0/8

!

interface FastEthernet1/0/8

shut

switchport mode access

switchport access vlan 1

switchport voice vlan 81

spanning-tree portfast

no shut

The purpose of this test is findout if its a port config problem.

[getamessay]

Dear Keanej,

No I don't use VLAN 1 as data VLAN. It was a type when I posted the config.  The port is configured for dynamic VLAN with VMPS support as follows:

switchport access vlan dynamic

[paolo bevilacqua]

I've seen this before...

can you please try removing all and any qos config from the switch ?

Or have you resolved already ?

[getamessay]

I did as you requested. It works the first time and then after a while I had same problem. Can I modify ARP or CAM timeout in Cat 3750?

Another observation: If I set the data VLAN to static on the port or connect a PC to the IP Phone, it is working.

[paolo bevilacqua]

So it seems related to dynamic VLAN, is that a absolute need for you?

Or try update IOS.

[getamessay]

I thought it was IOS issue and I updated it the latest version. As for dynamic VLAN, yes we need it. We run VMPS for data part.

[paolo bevilacqua]

Then if you're sure config is right, your only resolution is a TAC case.