I'm trying to setup a CentOS 7 DNS server in a VPN. I can't get devices from the VPN subnet (different subnet) to ping servers. I can get pings to work between servers (same subnet)
When I run tcpdump -nvi eth1 icmp I can see the following:
When 10.4.1.21 pings 10.4.1.2:
10:26:58.348366 IP (tos 0x0, ttl 64, id 20006, offset 0, flags [DF], proto ICMP (1), length 84)
10.4.1.21 > 10.4.1.2: ICMP echo request, id 17034, seq 1, length 64
10:26:58.348438 IP (tos 0x0, ttl 64, id 39037, offset 0, flags [none], proto ICMP (1), length 84)
10.4.1.2 > 10.4.1.21: ICMP echo reply, id 17034, seq 1, length 64
10:26:59.348266 IP (tos 0x0, ttl 64, id 20913, offset 0, flags [DF], proto ICMP (1), length 84)
10.4.1.21 > 10.4.1.2: ICMP echo request, id 17034, seq 2, length 64
10:26:59.348325 IP (tos 0x0, ttl 64, id 39998, offset 0, flags [none], proto ICMP (1), length 84)
10.4.1.2 > 10.4.1.21: ICMP echo reply, id 17034, seq 2, length 64
10:27:00.348248 IP (tos 0x0, ttl 64, id 21633, offset 0, flags [DF], proto ICMP (1), length 84)
10.4.1.21 > 10.4.1.2: ICMP echo request, id 17034, seq 3, length 64
10:27:00.348306 IP (tos 0x0, ttl 64, id 40058, offset 0, flags [none], proto ICMP (1), length 84)
10.4.1.2 > 10.4.1.21: ICMP echo reply, id 17034, seq 3, length 64
However, when 10.10.79.34 pings 10.4.1.2, all I see are requests but no replies
10:32:12.225281 IP (tos 0x0, ttl 127, id 3592, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 78, length 40
10:32:17.250644 IP (tos 0x0, ttl 127, id 3593, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 79, length 40
10:32:22.129885 IP (tos 0x0, ttl 127, id 3594, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 80, length 40
10:32:27.389271 IP (tos 0x0, ttl 127, id 3595, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 81, length 40
10:32:32.149386 IP (tos 0x0, ttl 127, id 3596, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 82, length 40
10:32:37.269775 IP (tos 0x0, ttl 127, id 3597, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 83, length 40
10:32:42.157175 IP (tos 0x0, ttl 127, id 3598, offset 0, flags [none], proto ICMP (1), length 60)
10.10.79.34 > 10.4.1.2: ICMP echo request, id 1, seq 84, length 40
It seems to me that the CentOS server is swallowing the requests. I can't find anything in the logs to help so far. I've got the firewall turned off.
The laptop at 10.10.79.34 is able to ping the gateway at 10.4.1.1.
