A lot of people just have a -j DROP to drop all unwanted traffic or traffic not explicitly allowed but there is a better solution if you want real and proper logging:
Here is another example of more advanced iptables rules.
Take an example iptables rules file
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -i eth1 -p icmp -j ACCEPT........
Sep 12 18:16:25 vps pluto[7299]: ERROR: asynchronous network error report on eth0 (sport=500) for message to 192.5.6.2 port 20640, complainant 192.5.6.2: Connection refused [errno 111, origin ICMP type 3 code 3 (not authenticated)]
Some say changing the "leftprotoport=17/%any" will fix this but I have not found this to be the case.
Essentially it means at least one end is blocking the ipsec packets. Sometimes the %any allows an alt........
That is pinging to the gateway IP on the same switch, the same IP is pingable externally without any problems which makes me think the switch is fine.
64 bytes from 55.55.55.55: icmp_seq=4 ttl=255 time=1.07 ms
64 bytes from 55.55.55.55: icmp_seq=1 ttl=255 time=3536 ms
64 bytes from 55.55.55.55: icmp_seq=2 ttl=255 time=2536 ms
64 bytes from 55.55.55.55: icmp_seq=3 ttl=255 time=1536 ms
64 bytes from 55.55.55.55: icmp_seq=8 ttl=255 time=1.20 ms
64 by........