Home » Kerio User Forums » Kerio Operator » Dropped calls over VPN (Calls dropping over vpn connection)

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I'm experiencing a lot of dropped calls in my system. It seems similar to what other users have experienced on this forum, but I haven't seen any resolutions. We have a multi-site set up with VPN connections between sites and it's only calls between these sites that are dropping.

Here is the warning I see in the logs when this happens.

[04/Feb/2015 16:48:28] asterisk[2293]: WARNING[2463]: chan_sip.c:3841 in retrans_pkt: Retransmission timeout reached on transmission 0487baf7130fe7c4206a2cce1ff5c5ba<_at_> for seqno 102 (Critical Request)

It is a bit random so capturing packets during one of these calls has been difficult, but I will keep trying.

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According to some past cases that I've had a look at, this may be caused by one of the following:

a) an invalid public IP address configured in Operator
b) extensions not marked as behind NAT when they are and should be marked as such
c) a device on the route is discarding the SIP packets

One suggestion that appeared to resolve the issue in another case was to focus on the Firewall rather than Operator and make sure that:

a) packets coming from Operator have a static public IP address
b) packets leave the firewall using one interface (there is no load balancing active, etc.)
c) the firewall is not dropping some packets

[Updated on: Thu, 05 February 2015 18:35]

Ken Snyder

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Thanks. I'll take a look at each suggestion. The public IP is definitely valid and static, but I'll check the individual extension settings and firewall.
Filip Jenicek (Kerio)

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assuming the sites are interconnected via VPN and the phones are in one network and can reach Operator, the extensions should not be marked as behind NAT.

It sounds to me more like that the VPN is dropping some packets. I think our best shot is the packet dump. You can limit it to port 5060 and leave it running for some time. It shouldn't be that space demanding then.

ICT and Me

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And is there a VoIP QoS/Reserve Bandwidth defined on the VPN tunnels.
I can imagine if there is also data traffic on the VPN tunnels and no QoS/Reserve Bandwidth the data push on full and there is no bandwidth left for VoIP traffic.

ICT and Me
Carlo Turk
The Netherlands
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