= SNMP Hands - On =

=== Goals ===
- Install and learn to use the SNMP commands
- Install vendor specific MIBs and use those with the SNMP commands

=== Notes ===
- For below hands-on we will be using Ubuntu 20.04 version.
- If you are installing snmp client (manager) tools on a remote server/computer you will need to connect the server through a SSH connection.

== Installing SNMP Client (Manager) tools ==

Connect to the server which will be used as the NMS (Network Management Station) and Open the Terminal program.

Update your software package repository
{{{
$ sudo apt-get update
}}}
This might take a few moments if everyone in class is doing this at the same moment.

Install the net-snmp tools:
{{{
$ sudo apt-get install snmp
$ sudo apt-get install snmp-mibs-downloader
}}}
The second of the two commands downloads the standard IETF and IANA SNMP MIBs which are not included by default.

Now, edit the file /etc/snmp/snmp.conf:
{{{
$ sudo vi /etc/snmp/snmp.conf
}}}

Note: Here we are using '''vi''' editor. You can use any text editor you are familiar with

Change this line:
{{{
mibs :
}}}

so that it looks like:
{{{
# mibs :
}}}

(You are "commenting out" the empty mibs statement, which was telling the snmp* tools not to automatically load the mibs in the /usr/share/mibs/ directory)

=== User specific SNMP configurations ===
Now, in your home directory make a .snmp directory with file snmp.conf inside it, make it readable only be you, and add the credentials to it:
{{{
$ cd
$ mkdir .snmp
$ chmod 700 .snmp/
$ vi .snmp/snmp.conf
}}}


Put the following contents in the file:
{{{

defVersion 3

# SNMP v3 Configurations
defSecurityLevel authNoPriv
defSecurityName admin
defAuthPassphrase <class passowrd>
defAuthType SHA

# SNMP v2c default community string
defCommunity <class passowrd>

}}}

== Configuration of SNMP Agent on Routers and Switches ==

==== Cisco ====

connect to your router and go to configure mode.
{{{
Router> enable

Router# configure terminal
}}}
Now we need to add an Access Control List rule for SNMP access, turn on SNMP, assign a read-only SNMP community string as well as a SNMPv3 group and user and tell the router to maintain SNMP information across reboots. To do this we do:
{{{
Router(config)# access-list 99 permit 192.248.6.0 255.255.255.0
Router(config)# snmp-server community <class passowrd> ro 99
Router(config)# snmp-server group ReadGroup v3 auth access 99
Router(config)# snmp-server user admin ReadGroup v3 auth sha <Class Password>
Router(config)# snmp-server ifindex persist
Now let's exit and save this new configuration to the routers permanent config.

Router(config)# exit
Router# write memory            
Router# exit       
}}}              

==== HP ====
Connect to the Router and go to config mode
{{{
<Router> system-view
}}}

Add the following configurations
{{{
[Router]acl number 2000
[Router-acl-basic-2000]rule 0 permit source 192.248.6.0 0.0.0.255
[Router]snmp-agent
[Router]snmp-agent community read <class passowrd>
[Router]snmp-agent sys-info version all
[Router]snmp-agent group v3 ReadGroup authentication acl 2000
[Router]snmp-agent usm-user v3 admin ReadGroup authentication-mode sha <class passowrd>
}}}

== Testing SNMP ==
Now we have both a SNMP Manager and SNMP Agent. To check that your SNMP installation works, run the snmpstatus command on the SNMP Manager host.

{{{
$ snmpstatus <IP_ADDRESS> 
}}}
Note that you just used was the SNMPv3 because we set the default version as SNMPv3. Try again, adding "-v2c" as a parameter. Notice that the command automatically uses the community string in the snmp.conf file instead of the v3 user credentials. Try "-v1".

To use the SNMP v2 or v1 we can add an option as below. Which will override the settings in the configuration file(/.snmp/snmp.conf).

snmpstatus -v2c <IP_ADDRESS> 
snmpstatus -v1 <IP_ADDRESS> 

Again we didn't want set Community string as it was set in the manager configuration file.

For the Router,
{{{
#snmpstatus <Router IP>
}}}

For the Switch,
{{{
#snmpstatus <Switch IP>
}}}

== Configuration of SNMP Agent on a Linux server ==

We also need to monitor the servers and workstations. Here we do this by installing and configuring a SNMP agent on a server.

Install the SNMP agent (daemon) on your host

{{{
$ sudo apt install snmpd
$ sudo apt install libsnmp-dev
}}}

Before making any changes to configurations files of a new installation it is a good practice to backup the original configuration.

{{{
$ cd /etc/snmp
$ sudo mv snmpd.conf snmpd.conf.orig
$ sudo nano snmpd.conf
}}}

Now enter the below configurations,

{{{
#  Listen for connections on all interfaces (both IPv4 *and* IPv6)
agentAddress udp:161,udp6:[::1]:161

# For SNMPv2: Configure Read-Only community and restrict who can connect
rocommunity <class passowrd>  192.248.6.0/24
rocommunity <class passowrd>  127.0.0.1

# Information about this host
sysLocation    LEARN Workshop
sysContact     sysadm@ws.ac.lk

# Which OSI layers are active in this host
# (Application + End-to-End layers)
sysServices    72

# Include proprietary dskTable MIB (in addition to hrStorageTable)
includeAllDisks  10%
}}}
Now save and exit from the editor.

Now we will add the same SNMPv3 user to your PC. We need to stop snmpd before adding the user, and restart it to read the above changes as well as the new user:
{{{
$ sudo service snmpd stop
$ sudo net-snmp-create-v3-user -a SHA -A <class password> admin
$ sudo service snmpd start
}}}

Check that snmpd is working:
{{{
$ snmpstatus localhost
}}}

Test your neighbors
{{{
$ snmpstatus <Neighbor IP Address>
}}}