On 10 February 2015 at 09:02, jg <webaccounts...@jgoettgens.de> wrote:
> > >> >> I get an occasional similar problem, we have Mikrotik firewalls and from >> tcpdump monitoring on the asterisk boxes I can see that the firewall >> (unbidden) has changed the IAX port. Usually a firewall reset and sometimes >> PBX reset combination fixes it. >> >> Its odd as its only one direction, occurs rarely and with no obvious >> driver. So IAX is happy in one direction but not the other. And I can see >> packets in the unhappy point arriving on the wrong port. >> >> I couldn't fix it without kicking the router/firewall so I would say its >> a router problem in the Destination NAT process. >> >> Cheers Duncan >> >> >>> Port is changed when NAT is applied from LAN to WAN. >>> While UDP session is maintained as ESTABLISHED, that port should not >>> change. >>> >>> If your peer changes constantly of session port could be UDP session >>> is too short in NAT table on routers. >>> You can try setting qualify=1000 (which is in ms. Default is 2000), >>> and see if peer keeps same port. >>> >>> Regards. >>> >>> voip-info.org also has an entry about general NAT related issues, > which could be relevant here > > I do not seem to have problems with Netgear firewalls, but other firewalls > show this effect. So far it happened only on a single side, such that calls > work from the other side. I already checked the open ports with > nc/ncat/netcat as UDP sender and receiver on the other end. The ports are > open, even when the arbitrary ports are used by Asterisk. > > I'll need to read a bit more and evaluate my pcap traces and possibly ask > the router vendors. > > Thank you for your efforts. > > jg > > > > > Some firewalls have a 'consistent NAT' option that needs to be enabled, otherwise you get the symptoms described. -- Ishfaq Malik Department: VOIP Support Company: Packnet Limited t: +44 (0)845 004 4994 f: +44 (0)161 660 9825 e: i...@pack-net.co.uk w: http://www.pack-net.co.uk Registered Address: PACKNET LIMITED, Duplex 2, Ducie House 37 Ducie Street Manchester, M1 2JW COMPANY REG NO. 04920552
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