Can't connect between droplets using public IP
I’m randomly having problems connecting between droplets via the public IP. I can connect to all droplets from my local machine (ping, SSH, etc) but between SOME droplets I cannot connect when using the public IP. Private IP seems unaffected:
[root@docker-2 ~]# ping 184.108.40.206 PING 220.127.116.11 (18.104.22.168) 56(84) bytes of data. From 22.214.171.124 icmp_seq=1 Destination Host Unreachable
(126.96.36.199 is the public IP for another node, which I can ping and SSH to from my local machine directly using this IP)
But I can ping the same machine using it’s private IP:
[root@docker-2 ~]# ping 10.130.73.188 PING 10.130.73.188 (10.130.73.188) 56(84) bytes of data. 64 bytes from 10.130.73.188: icmp_seq=1 ttl=64 time=1.72 ms
(10.130.73.188 is the private IP of 188.8.131.52)
This droplet is able to ping other servers over the internet, e.g.
[root@docker-2 ~]# ping 184.108.40.206 PING 220.127.116.11 (18.104.22.168) 56(84) bytes of data. 64 bytes from 22.214.171.124: icmp_seq=1 ttl=60 time=0.922 ms
There are no DO firewalls applied to any servers. All servers are Centos 7 with no firewalld and no custom networking rules applied, aside from those set up by Docker.
This seems to be random, since if I kill the droplet and reconfigure it, it sometimes starts to work. All droplets are configured by ansible and should be identical, yet some exhibit this problem and some do not.
Here’s a tracepath result from the same droplet, showing first another droplet I can’t reach and 2nd a droplet that I can reach. All 3 are in the same datacenter and all configured identically:
[root@docker-2 ~]# tracepath 126.96.36.199 1?: [LOCALHOST] pmtu 1500 1: 188.8.131.52 5.782ms 1: 184.108.40.206 8.442ms 2: 220.127.116.11 0.553ms 3: no reply 4: no reply 5: no reply
[root@docker-2 ~]# tracepath 18.104.22.168 1?: [LOCALHOST] pmtu 1500 1: 22.214.171.124 17.165ms 1: 126.96.36.199 3.751ms 2: 188.8.131.52 0.519ms 3: 184.108.40.206 0.432ms 4: 220.127.116.11 0.835ms reached Resume: pmtu 1500 hops 4 back 4
Please help. I’m new to DO and surprised how long it takes to get a support ticket answered so I’m trying here.