I'm currently attempting to implement DMVPN between a 2621(12.3(26)) and a 3640(12.4(23); head-end) over the Internet. I'm currently seeing an issue when the 2621 initiates the ISAKMP SA, the 3640 receives the correct packet, but the wrong sport is indicated.
received packet from X.X.X.X dport 500 sport 1 Global (R) MM_SA_SETUP
sending packet to X.X.X.X my_port 500 peer_port 1 (R) MM_SA_SETUP
The 2621 is specifying a dport of 500 with a sport of 500 in the debug output. The 3640 continues with the next few steps of the ISAKMP negotiation, but sends the reply back to the 2621 on port 1 instead of port 500.
Has anyone seen this and/or can assist with this? I've looked around a bit and I've not found another similar instance of this issue. Any assistance is appreciated. Thank you.