How do I enable SNMP on a Cisco 2620 for bandwidh monitoring?

Posted on 2004-04-15
Last Modified: 2012-06-27

I'd like to use PRTG to monitor bandwidth on several segments. I need to enable SNMP on my Cisco 2620 routers. I can log into the router but don't know to much about what to do next. I do on the other hand, know enough to be dangerous. I have an idea of what to do but I'm afraid I'll mess something up in the process. Also, will I have any trouble monitoring the traffic of 192.168.x.x if I'm on the 192.168.y.y segment?


Question by:Norris04
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LVL 27

Accepted Solution

pseudocyber earned 125 total points
ID: 10833827
In global exec mode, enter config mode by typing "config t".

In config mode, configure SNMP paramaters by typing: "snmp-server" followed by a space and parameters.

Router#config t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#snmp-server ?
  chassis-id        String to uniquely identify this chassis
  community         Enable SNMP; set community string and access privs
  contact           Text for mib object sysContact
  enable            Enable SNMP Traps or Informs
  engineID          Configure a local or remote SNMPv3 engineID
  group             Define a User Security Model group
  host              Specify hosts to receive SNMP notifications
  ifindex           Enable ifindex persistence
  inform            Configure SNMP Informs options
  location          Text for mib object sysLocation
  manager           Modify SNMP manager parameters
  packetsize        Largest SNMP packet size
  queue-length      Message queue length for each TRAP host
  system-shutdown   Enable use of the SNMP reload command
  tftp-server-list  Limit TFTP servers used via SNMP
  trap              SNMP trap options
  trap-source       Assign an interface for the source address of all traps
  trap-timeout      Set timeout for TRAP message retransmissions
  user              Define a user who can access the SNMP engine
  view              Define an SNMPv2 MIB view

LVL 79

Assisted Solution

lrmoore earned 125 total points
ID: 10833984
To expand on what pseudocyber posted...

all you really need is a Read-Only community string and snmp enabled. This is accomplished with just one line:

snmp-server community <string> RO

Replace <string> with whatever you like. Treat snmp communities as passwords and use strong password practices. i.e.

snmp-server community Go0DPa$$Word! RO

No problems reading the snmp statistics from any other subnet with this config.


Author Comment

ID: 10841914
OK, It looks like the command was accepted, but my monitoring package will not connect with the router. When I do a sh snmp I get:

26 SNMP packets input
    0 Bad SNMP version errors
    26 Unknown community name
    0 Illegal operation for community name supplied
    0 Encoding errors
    0 Number of requested variables
    0 Number of altered variables
    0 Get-request PDUs
    0 Get-next PDUs
    0 Set-request PDUs
0 SNMP packets output
    0 Too big errors (Maximum packet size 4096)
    0 No such name errors
    0 Bad values errors
    0 General errors
    0 Response PDUs
    0 Trap PDUs

SNMP logging: disabled

Does this indicate that snmp is enabled? If not, what command should I give to show the snmp status.



LVL 27

Expert Comment

ID: 10841947
The error looks like they're not agreeing on the community string.  I would set it for something simple until you get it working, and then change it to be more secure.
LVL 79

Expert Comment

ID: 10842197
>  26 Unknown community name

Looks like your PRTG package is trying to use something like "public" as the community string. Whever you see "public" in the PRTG config files, replace that with your Go0DPa$$Word!

"public" is typically the well-knnown default read-only community string and the first thing that anyone would try. "private" is the default read-write community string for most equipment.

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