Server showing as down in Host groups but the Check_mk service is green

[PrachiKatakwar]

Hi Team,
We are using Checkmk Raw Edition 2.1.0p5 on a physical server.
In the host groups, the server is in down state, so I ran the connection tests and yes, the ping is not reachable from the checkmk server and so the host is in down state.

My concern is then the Check_MK service for that host should be red but it’s showing as green …why??

BR
//Prachi

[r.sander (Robert Sander)]

The host check is separate from the agent query and usually done by ICMP (ping).

[PrachiKatakwar]

Hi ,
On further troubleshooting, I could see on the agent port 6556 is listening but on Ipv6

, is this the reason the connection test is failing?

Also, from the checkmk server, if I check the connectivity to the agent its perfectly fine

Somewhere I am not understanding that why the connection test is failing , the only thing that comes into my mind is IPV6…

BR
//Prachi

[r.sander (Robert Sander)]

There is a difference between TCP Port 6556 and ICMP (ping requests).

[PrachiKatakwar]

Hi ,
Ok, that means apart from TCP 6556 port to be opened from source server (checkmk) to agents, do we need some other ports also to be opened from source to destination for ICMP ping request?

BR
//Prachi

[paulr282 (Paul Rost)]

ICMP does not use a specific port. You need to check your firewall and/or the destination system if it answers on a ping.

[PrachiKatakwar]

ok, well I disabled the firewall both on source (checkmk) and destination(agent) but still from checkmk I am unable to ping the destination , that means there is some firewall between them which blocking the ICMP /ping request.

BR
//Prachi

[PrachiKatakwar]

Hi,

Thank you so much. We can close this, its resolved.

Solution: Apart from opening port TCP 6556 from source (checkmk server) to destination(agents), we also need to check the ping works from source to destination otherwise the host will appear as down.
You need to contact your network team if there is any blockage/firewall between source and destination if the ping doesn’t work.

BR
//Prachi

[Marcuslayne (marcus)]

I know this is closed. I am also running the RAW version. I had this happen to me. I just SSH’d into the checkmk server and ran the ping command to the target host. Starting pinging from the checkmk application almost right away.