Howto created by
fmangeant at Cacti
This HowTo will explain how to use SSH tunnels to graph a Unix server that isn't directly reachable by your Cacti server :
In this example, the Cacti server can reach the Gateway, which can reach the target server.
On Gateway, create a "cactiuser" user :
# useradd -d /home/cactiuser -m cactiuser
Then you have to generate SSH keys (without passphrase) :
# su - cactiuser $ ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/cactiuser/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/cactiuser/.ssh/id_rsa. Your public key has been saved in /home/cactiuser/.ssh/id_rsa.pub. The key fingerprint is: 40:f6:91:a1:2d:d1:46:d4:76:e3:d8:c6:3f:c2:cf:f2 [email protected] ```console The public key of the "cactiuser" user has then to be authorized as an input key : ```console $ cd $HOME/.ssh $ cp -p id_rsa.pub authorized_keys
Finally, create the SSH tunnel :
# su - cactiuser -c "ssh -f -N -g -L 192.168.0.2:10000:192.168.1.2:161 [email protected]"
This SSH tunnel will forward all packets sent to 192.168.0.2 on TCP port 10000, to 192.168.1.2 on port TCP 161.
The options that are used are the following :
-f : requests SSH to go to background just before command execution -N : do not execute a remote command -g : allows remote hosts to connect to local forwarded ports -L : specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side.
You can add this command to
/etc/rc.local, so it will be executed at boot time.
By default, the Net-SNMP agent listens on UDP port 161; we'll modify its configuration to listen on TCP port 161.
To do so, use that in
snmpd.conf on the target server :
agentaddress tcp:161 rocommunity mycommunity
For a more detailed configuration of snmpd.conf, follow the Net-SNMP guide in the manual
From the Gateway host, run this command :
$ snmpwalk -v 1 -c mycommunity tcp:192.168.1.2 sysname SNMPv2-MIB::sysName.0 = STRING: target_server
From the Cacti server, run this command :
$ snmpwalk -v 1 -c mycommunity tcp:192.168.0.2:10000 sysname SNMPv2-MIB::sysName.0 = STRING: target_server
If everything works fine, your host is then ready to be added to Cacti.
If not, review your network configuration (firewall rules, especially).
In Cacti, create a new device like that :
Voila ! Your target server is graphed by Cacti :)