Hello All,
I have been troubleshooting an issues with Alcatel IP Phones for weeks now and it appears that the issue happens when the calls are made between the wireless phones the majority of the time. What's strange is that the one way audio happens for 30 secs and then everything works fine. I have done numerous packet captures ... details of the last test I did are below and the capture is attached ... it appears that the WLC is not responding to ARP Request sent by the phone that is experiencing the one way audio.
The issue that I am having is that this problem doesn't happen all the time. I have tested 4 IP Phones and I can have the issue happen with 2 of them while the other 2 phones work fine so that makes it appear to me that it's not an issues with the WLC because why would it respond to some ARP Requests and not others? This is the point that I am pondering so any help would be greatly appreciated! Again this the network is all Cisco (5508 WLCs with 3502i and 1142 APs; all Cisco Switches). I am not experiencing any issues with any other clients or vendors except the Alcatel IP Phones ... their engineers have asked me if I can turn off Proxy ARP on the WLC's and I told them that I don't believe I can with the 7.x code so now they have asked me if there is any reason why a WLC wouldn't respond to an ARP Request. I couldn't find any reason why it would but I don't have any basis to say that when the packet captures show the latter. At first I thought it was the P2P setting in the WLAN so I double checked and the P2P setting on the WLAN and it is disabled on all the WLCs. At this point I am not sure what to do or tell the vendor.
Here are the details of the phones under test:
8128 No1 Ext 6015 00:01:3e:3c:2d:05 10.170.240.252
8128 No2 Ext 6013 00:01:3e:3c:2d:85 10.170.241.57
AP BSSID 6C:50:4d:2b:67:3f
Packet capture file test_3_dmp.dmp (capture taken for both phones involved in the test calls)
- Call from 6015 to 6013. No audio from 6013 to 6015
- Frame 11865 First ARP request , from Phone 6013 , for mac of Phone 6015. Frame has a destination of Broadcast. Frame is ACKed by AP. There is no response. Timestamp is 9:19:34.
- Frames 12139, 12383, 12650, ...........24589, 24817. Other ARP requests for mac of Phone 6015. Frames have a destination of broadcast. Frames are ACKed by AP.
- Frame 24946 ARP request , from Phone 6015 , for mac of Phone 6013. To DS. Frame is ACKed by AP. Timestamp 9:20:05
- Frame 25068 ARP request , from Phone 6015 , for mac of Phone 6013. From DS. Frame is ACKed by Phone 6013. Timestamp 9:20:05
- Frame 25080 First RTP packet from Phone 6013 to 6015. Timestamp 9:20:05.
- Frame 25355 ARP Response from Phone 6013 to ARP request from 6015. To DS. Frame is ACKed by AP. Timestamp 9:20:05
- Frame 25447 ARP Response from Phone 6013 to ARP request from 6015. From DS. Frame is ACKed by Phone 6015. Timestamp 9:20:05
So for the period 9:19:34 to 9:20:05 The phone that no audio can be heard from, is repeatedly sending ARP requests for the mac address of Phone 2. A period of 30 seconds. Then at 9:20:05 , Phone 1 sends an ARP request to Phone 2. This ARP request contains the mac address and IP address of Phone 1. So now Phone 2 knows how to reach Phone 1 , despite not getting a response to its numerous ARP requests , and it starts sending RTP packets to Phone 1. At this point there is bidirectional audio.
Debug 00013e3c2d85 (capture taken from the debug from the controller)
Only Phone 2 was captured; however we see the same behaviour. i.e. Many ARP Request packets from Phone 1 for 30 seconds. no RTP, then a ARP request from Phone 2, then the RTP starts.
Again any suggestions would be greatly appreciated!!!!
Thanks,
Malwan
