Calls being dropped

Can anyone help me with this warning message:

Warning [6000]:Chan_sip.c:1949 retrans_pkt: maximum retries exceeded on transmission …

This message is followed with

Warning [6000]:Chan_sip.c:1973 retrans_pkt: Hang up call … no reply to our critical packet.

The receiving call gets terminated prematurely.

Thanks

Rgds,
Philip

Seems to be that packets are transmitted to incorrect destination or something is blocking them. May be NAT problem.

Use ‘sip set debug’ in CLI and see what messages are generated during call.

I have the same problem
In my office everything was ok, but when I put it in my customer’s office, this message appears.

chan_sip.c: Maximum retries exceeded on transmission …

read and follow my post above.

is the box behind NAT?

It wasn’t behind a nat, after changing to v.21 everything is ok.