SNMP

Simple Network Management Protocol (SNMP)

• Dedicated monitoring and management
• Read-Only mode for monitoring
• Read/Write mode for administration
  • As we query the device, we do this on a regular interval, this is called polling,, what this gives us over time is a baseline, so we know when things become weird.
• SNMPv3 offers encryption and authentication
• UDP 161 for management
• UDP 162 for notifications (TRAP)
  • SET is reaching out to the device to make a change
  • GET is when I say "Hey router, how is your CPU doing?"
  • TRAP - unsolicited notification
    • CPU levels at 82%, triggers TRAP when a threshold is met.

SNMP Components

• SNMP Client
• SNMP Server
• SNMP Management Information Base
  • Server is NMS - Network Management Station
    • SolarWinds is a good example of this.
  • SNMP clients could be swithces, routers, APs
    • When a servers talks to the client and sends a query, it needs to references its OID
      • A unique identifier for different things that you can ask for. That all live inside of this Management Information Base.
• SNMP Object ID
• "Polling"
• Community String
  • Is simply a password for SNMP
    • There is what we call the Public, and the Private
    • Public is Read Only (RO)
    • Private is Read Write (RW)
  • By default network devices have SNMP enable and their community string is set as public
  • Useful for verifying authorized devices in a network.

SNMP Read Only example

• Tell the NMS who the router is
  • Specify IP, Key, RO or RW on the router
  • Specify IP, Key, RO or RW on the server
    • We call this a community string
• Store results in a Data Base

SNMP Read Write example

• You can make changes
• Admin logins to NMS and it can push the changes to the device, maybe is a router
  • In this case we need the RW community string.