On Tue, Nov 12, 2013 at 6:05 PM, Hiers, David <David.Hiers at adp.com> wrote:
Maybe someone is spoofing your SBC IP address?
I can't see what useful info would be gained from such spoofing, but enough of these could DOS you pretty hard.
I would suggest capturing packets towards the devices experiencing it, behind the NAT device, using Wireshark ----- I would wonder first if either the NAT/ACL isn't working as designed; or traffic is coming from a SIP ALG / inside the NAT; spoofing the SBC's source IP seems terribly unlikely. I think it's more likely, there's an unexpected way the Polycom is being contacted, such as a proxy service on a router. Then there is that matter of; "Does your NAT device verify the foreign IP address of reverse traffic like a full stateful firewall would, or does it just check the destination port number on an incoming packet, and immediately translate to internal IP based on the destination port number and forward to the internal device?" In the latter case, the internal device might be contacted on port 5060 from other internet hosts scanning the ephemeral port range; if that 5060 from the internal device has recently been used as a source port from the Polycom contacting the SBC. So a full packet capture from the network with the handsets, could give you a better idea, of what you are seeing.
David
-- -JH