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Type:
Incident report
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Resolution: Won't fix
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Priority:
Critical
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None
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Affects Version/s: 2.4.5
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Component/s: Proxy (P)
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None
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Environment:Debian 7
Hello,
two days ago we updated our Zabbix Server and Proxys on Debian 7 from Zabbix 2.2.8 to Zabbix 2.4.5. Everything works fine and as expected. But I noticed one strange thing that drives me crazy.
Since I updated to 2.4.5 new hosts I add, or old hosts which got a new IP from me, can't get monitored anymore. They all switch to: "Zabbix agent on FQDN is unreachable for 5 minutes"
I checked everything twice. I can ping them. Port 10050 is reachable via telnet test. Der Service Agent is up, running and listening. But the Server simply won't talk to the agent. Finally I started TCPDUMP on the zabbix proxy, and I found out, that the server never tries to contact the agent.
192.168.23.126 - Zabbix Proxy
192.168.23.18 - A Windows Server
00:21:30.918806 IP 192.168.23.18.49783 > 192.168.23.126.10051: Flags [.], ack 1, win 2053, length 0 00:21:30.918834 IP 192.168.23.18.49783 > 192.168.23.126.10051: Flags [P.], seq 1:6, ack 1, win 2053, length 5 00:21:30.918841 IP 192.168.23.126.10051 > 192.168.23.18.49783: Flags [.], ack 6, win 457, length 0 00:21:30.918980 IP 192.168.23.18.49783 > 192.168.23.126.10051: Flags [P.], seq 6:104, ack 1, win 2053, length 98 00:21:30.919007 IP 192.168.23.126.10051 > 192.168.23.18.49783: Flags [.], ack 104, win 457, length 0 00:21:30.919553 IP 192.168.23.126.10051 > 192.168.23.18.49783: Flags [P.], seq 1:6, ack 104, win 457, length 5 00:21:30.919582 IP 192.168.23.126.10051 > 192.168.23.18.49783: Flags [FP.], seq 6:50, ack 104, win 457, length 44 00:21:30.919891 IP 192.168.23.18.49783 > 192.168.23.126.10051: Flags [.], ack 51, win 2052, length 0 00:21:30.919906 IP 192.168.23.18.49783 > 192.168.23.126.10051: Flags [F.], seq 104, ack 51, win 2052, length 0 00:21:30.919914 IP 192.168.23.126.10051 > 192.168.23.18.49783: Flags [.], ack 105, win 457, length 0
As you see, the traffic comes from the agent, which is looking for active checks. But never the proxy which tries to fetch agent data.
If I TCPDUMP some "old" host which I did not change since the update, I see alot of traffic into the other direction:
00:28:40.009008 IP 192.168.23.126.33133 > 192.168.23.10.10050: Flags [.], ack 1, win 457, options [nop,nop,TS val 1220126714 ecr 51375085], length 0 00:28:40.009382 IP 192.168.23.126.33133 > 192.168.23.10.10050: Flags [P.], seq 1:22, ack 1, win 457, options [nop,nop,TS val 1220126714 ecr 51375085], length 21 00:28:40.010007 IP 192.168.23.10.10050 > 192.168.23.126.33133: Flags [P.], seq 1:6, ack 22, win 260, options [nop,nop,TS val 51375085 ecr 1220126714], length 5 00:28:40.010031 IP 192.168.23.10.10050 > 192.168.23.126.33133: Flags [FP.], seq 6:15, ack 22, win 260, options [nop,nop,TS val 51375085 ecr 1220126714], length 9 00:28:40.010048 IP 192.168.23.126.33133 > 192.168.23.10.10050: Flags [.], ack 6, win 457, options [nop,nop,TS val 1220126714 ecr 51375085], length 0 00:28:40.010067 IP 192.168.23.126.33133 > 192.168.23.10.10050: Flags [F.], seq 22, ack 16, win 457, options [nop,nop,TS val 1220126714 ecr 51375085], length 0 00:28:40.010203 IP 192.168.23.10.10050 > 192.168.23.126.33133: Flags [.], ack 23, win 260, options [nop,nop,TS val 51375086 ecr 1220126714], length 0
Seems like a major bug to me?