Ping: sendto: no buffer space available

[decibel83]

Hi.
I'm having a strange problem on my pfSense system.
I configured the LAN and the WAN interface, and the cable are working without any problems.
The LAN network is working good, but the WAN network not.
If I ping the default gateway or an external host I obtain the following error:

[root@fw]/root(2): ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available

[root@fw]/root(3): ping 123.123.123.89
PING 123.123.123.89 (123.123.123.123): 56 data bytes
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available

If I try to ping another host on the WAN network, all work good:

[root@fw.radiodolomiti.local]/root(4): ping 123.123.123.90
PING 123.123.123.90(213.21.190.90): 56 data bytes
64 bytes from 123.123.123.90: icmp_seq=0 ttl=64 time=0.113 ms
64 bytes from 123.123.123.90: icmp_seq=1 ttl=64 time=0.107 ms
64 bytes from 123.123.123.90: icmp_seq=2 ttl=64 time=0.110 ms
64 bytes from 123.123.123.90: icmp_seq=3 ttl=64 time=0.111 ms

The network on the WAN interface is 123.123.123.88/255.255.255.248.
The Internet connection is not working, of course.

Could you help to understand and solve this problem, please?

Thank you very much!
Bye.

[jimp]

Usually that indicates that it can't send traffic there. Either because it doesn't have permission (blocked by firewall rules) or perhaps because it doesn't have a default route going that way.