ISAKMP on UDP port 500? : sysadmin
FVS336g V1 -UDP PORT 500 - NETGEAR Communities re: fvs336g v1 -udp port 500 It's the end of 2014 and I just upgraded our NETGEAR ProSafe™ Gigabit 8 Port VPN Firewall FVS318G to the latest firmware which makes connection more robust. Though, we now have the same issue i.e. UDP 500 forward ot possible due to being used by VPN IKE. Configure Windows Firewall - SQL Server | Microsoft Docs Dec 13, 2019 sockets - udp client sending ICMP "port unreachable" when i see that it is the only possible explanation, but I don't see how that could be, because I explicitly accept the source port. also I accept all established/related states, which should implicitly cover this case too (iptables remembers IP/Port pairs for stateless "connections" like UDP). – nonchip Jul 13 '14 at 7:07 How to Find Open and Blocked TCP/UDP Ports
Oct 10, 2018
Feed Detail UDP port 500 is the ISAKMP port for establishing PHASE 1 of IPSEC tunnnel. VPN-GW1-----nat rtr-----natrtr-----VPNGW2. If two vpn routers are behind a nat device or either one of them, then you will need to do NAT traversal which uses port 4500 to successfully establish the complete IPEC tunnel over NAT devices.
Dec 13, 2019
How to set up VPN server with port forwarding? | Official