First post - but I wonder if someone can help me troubleshoot a VoIP issue with EX-4300 switches and a Mitel phone system.

Quick overview of configuration Mitel PBX (VM) hosted at datacentre, main office has a L2 link of 500Mbps, supports 400 handsets with no issue & ~20 concurrent teleworkers, all OK

Branch office - 2 x SRX240 firewalls in active/passive cluster 2 x EX4300 switches in a virtual chassis 2 x handsets (Mitel 5360) 2 x Polycoms in SIP mode 30Mbps link to ISP IPsec VPN to datacentre, through which the voice SIP/Mitel routes Total bandwidth utilisation is low, not a contention issue Separate VLANs for voice, data, server, wifi

Issue When making a call from a handset in the branch office to another handset in the main office (direct UDP traffic), the audio drops at ~3-5 minutes for around 20 seconds, then returns. The same happens with the Polycoms using SIP I configured the handsets to use Teleworker mode, and get the same result

I configured port mirroring for one of the handsets and ran a capture. Regular conversation shows 1-2 UDP packets in both directions, but when the silence occurs I see only the local handset transmitting UDP packets, nothing coming from the remote end.

Then I configured the port mirror on the uplink between the switch and the firewalls and ran a capture, again normal conversation shows 1 or 2 packets in both directions until the silence - but then, I see packets coming from the remote handset being repeated, but nothing locally going back out.

So it appears the packets are being lost in the switch. We can't set full CoS end to end due to the L3 link at the branch office, and I have set the voice ports for expedited forwarding and verified this in the interface queues.

Can anyone shed any light on where else to start digging? I'm kind of new to Junos so also trying to learn this at the same time...

Thanks