Ubuntu OS connectivity issue with port 5666 in Nagios

[tssnagiosadmin]

Hello Nagios,

Please assist. We have two servers running in Ubuntu OS. However, we are having issue in monitoring with port 5666 connectivity issue in Nagios. Currently, theses two servers are not pin-gable. IP address and hostname are already in /etc/hosts. We also attached the screenshot for the errors encountered.

[root@sgisgnagtstrm01 vmadmin]# cat /etc/hosts | grep -i azisgezrxcpq02
10.10.20.12 azisgezrxcpq02
[root@sgisgnagtstrm01 vmadmin]# cat /etc/hosts | grep -i azisgezrxcpq01
10.10.20.11 azisgezrxcpq01
[root@sgisgnagtstrm01 vmadmin]# ping azisgezrxcpq02
PING azisgezrxcpq02 (10.10.20.12) 56(84) bytes of data.
^C
--- azisgezrxcpq02 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

[root@sgisgnagtstrm01 vmadmin]# ping azisgezrxcpq01
PING azisgezrxcpq01 (10.10.20.11) 56(84) bytes of data.
^C
--- azisgezrxcpq01 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms



Regards,
TSS MNL

[mbellerue]

Can you ping the Ubuntu servers from anywhere else on the network? Is ufw running on the Ubuntu systems (systemctl status ufw)?

[tssnagiosadmin]

Hello mbellerue,

Thank you for the quick response.

I tried to ping the Ubuntu servers from a different server but it is unreachable. In this case, we'll also check with our network team.

For ufw, I tried to run it on both Ubuntu servers, and this is the output I got.

azisgezrxcpq01

vmadmin@azisgezrxcpq01:/etc$ ps -ef | grep ufw
vmadmin 77660 72325 0 17:57 pts/19 00:00:00 grep --color=auto ufw
vmadmin@azisgezrxcpq01:/etc$ systemctl status ufw
● ufw.service - Uncomplicated firewall
Loaded: loaded (/lib/systemd/system/ufw.service; enabled; vendor preset: enabled)
Active: active (exited) since Wed 2019-09-11 00:44:18 UTC; 1 months 12 days ago
Docs: man:ufw(8)
Main PID: 549 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 19660)
CGroup: /system.slice/ufw.service

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.


azisgezrxcpq02

root@azisgezrxcpq02:/etc# ps -ef | grep ufw
root 101841 108114 0 17:59 pts/17 00:00:00 grep --color=auto ufw
root@azisgezrxcpq02:/etc# systemctl status ufw
● ufw.service - Uncomplicated firewall
Loaded: loaded (/lib/systemd/system/ufw.service; enabled; vendor preset: enabled)
Active: active (exited) since Thu 2019-09-12 08:43:58 UTC; 1 months 10 days ago
Docs: man:ufw(8)
Main PID: 526 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 19660)
CGroup: /system.slice/ufw.service

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

Regards,
TSS MNL

[mbellerue]

Okay, we'll wait to hear back. If you're talking to your networking team, you might also just make sure that you will be able to access the servers via TCP port 5666 from your Nagios server.

[tssnagiosadmin]

Hello mbellerue,

From network side, it was running fine. We are now able to ping Nagios from Ubuntu servers.

Code: Select all

 root@azisgezrxcpq01:/home/vmadmin# ping 10.10.13.7
PING 10.10.13.7 (10.10.13.7) 56(84) bytes of data.
64 bytes from 10.10.13.7: icmp_seq=1 ttl=63 time=1.69 ms
64 bytes from 10.10.13.7: icmp_seq=2 ttl=63 time=1.75 ms
^C
--- 10.10.13.7 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 1.696/1.724/1.753/0.050 ms

However, when we tried to do ping Ubuntu servers from Nagios, we got connection error.

Code: Select all

[root@sgisgnagtstrm01 vmadmin]# ping azisgezrxcpq01
PING azisgezrxcpq01 (10.10.20.11) 56(84) bytes of data.
^C
--- azisgezrxcpq01 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2000ms

[root@sgisgnagtstrm01 vmadmin]# ping 10.10.20.11
PING 10.10.20.11 (10.10.20.11) 56(84) bytes of data.
^C
--- 10.10.20.11 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 999ms

We also run a telnet from Nagios to Ubuntu servers using port 5666 but still error in connection.

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[root@sgisgnagtstrm01 vmadmin]# telnet 10.10.20.11 5666
Trying 10.10.20.11...
telnet: connect to address 10.10.20.11: Connection refused
[root@sgisgnagtstrm01 vmadmin]#

[lmiltchev]

Can you run the following command on both Ubuntu machines and show the output?

Code: Select all

ufw status

Have you tried temporarily disabling the firewall to see if you will be able to ping these boxes from the Nagios XI server?

Code: Select all

ufw disable

[tssnagiosadmin]

I just run the command for "ufw status" and this was the output.

azisgezrxcpq01

Code: Select all

root@azisgezrxcpq01:/home/vmadmin# ufw status
Status: inactive

azisgezrxcpq02

Code: Select all

root@azisgezrxcpq02:/home/vmadmin# ufw status
Status: inactive

Prior in running the "ufw status" the firewall was already disabled. Also, I tried to run the "ufw disable" command and run a telnet from Nagios XI server to Ubuntu, still got the error.

[lmiltchev]

This has to be either a networking issue or a firewall issue. Can you show us the network settings from the Ubuntu machines? On Ubuntu 18, there should be a xxx.yml file in /etc/netplan directory. Also, run:

Code: Select all

ip addr

on the Nagios XI server, and on both Ubuntu machines, and show the output.

Do you have another firewall between the Nagios XI server, and Ubuntu boxes (or another device) that could be blocking the connection?

[tssnagiosadmin]

These are the network setting of Ubuntu servers:

azisgezrxcpq01

root@azisgezrxcpq01:/etc/netplan# cat 50-cloud-init.yaml
# This file is generated from information provided by
# the datasource. Changes to it will not persist across an instance.
# To disable cloud-init's network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
ethernets:
eth0:
dhcp4: true
match:
macaddress: 00:0d:3a:a0:c9:f5
set-name: eth0
version: 2

azisgezrxcpq02

root@azisgezrxcpq02:/etc/netplan# cat 50-cloud-init.yaml
# This file is generated from information provided by
# the datasource. Changes to it will not persist across an instance.
# To disable cloud-init's network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
ethernets:
eth0:
dhcp4: true
match:
macaddress: 00:0d:3a:08:86:cc
set-name: eth0
version: 2

Do you have another firewall between the Nagios XI server, and Ubuntu boxes (or another device) that could be blocking the connection?

- None.

Please see attachment for the ip addr result.

[scottwilkerson]

You showed a cloud-init configuration, are these running in a clout? If so, they usually have a firewall and you need to specifically allow ports/protocols to be allowed in security groups for the instance.