Azure Load Balancer Health Prob 22 Creating Log "Did not receive identification string

Question

We have Azure Load Balancer which needs to be redirect traffic any of the Healthy IPTABLE Servers (Total 2 IPTABLE Servers). From IPTABLE server traffic will be forwarded to Other Production Servers (Which are not accessible Directly).

We have configured port 22 as health probe on Azure Load Balancer. Because of this we are getting logs created like following on Production Servers.

2019-04-27T05:52:29.443677-05:00 azneqodrt001 sshd[35446]: Did not receive identification string from 10.16.10.12

Alternatively, We have created custom port 5500 using nc command. Again we have reconfigured Load Balancer health probe with port 5500 (on IPTABLE Servers) instead of 22. But it was worked only for few minutes. Later it stopped working.

Can anyone suggest any alternative for this kind of situation.

Answer 1

Two alternatives:

• whatever useful are "IPTABLE" servers serving besides port 22, try to healthcheck that useful service; for example if they are translating (doing NAT) a port like 80 to some other port, then check port 80; it's not so good to check 22 if the customer needs 80

• if you need to have that fake healthcheck port, use nc -k -l 5500; the -k will make it stay for more than one connection; best would be to set up a systemd unit, so it could autostart it as well as restart on failure