SNMP packet size

[fazmibakar]

Hi Guys,

Anyone know the size of the SNMP packet? how to know the SNMP packet size?

thank you

[daniel.dib]

It will depend on how much information is being sent. It's not a fixed size. The only certain part is that there is an UDP header. If you want to see the packet you need to perform a capture. Is there any specific reason why you want to know the packet size?

Daniel Dib
CCIE #37149

[fazmibakar]

actually i want to enable SNMP for access switches about 100 unit. this is for NMS (non cisco). is it the SNMP packet will affect the network performance?

[sathvik k v]

Hi

Default packet size is 1500. This can be changed using snmp-server packetsize command. Have taken some text from the below mentioned URL please refer.

http://www.cisco.com/en/US/docs/ios/netmgmt/command/reference/nm_20.html#wp1012810

snmp-server packetsize

To establish control over the largest Simple Network Management Protocol (SNMP) packet size permitted when the SNMP server is receiving a request or generating a reply, use the snmp-server packetsize command in global configuration mode. To restore the default value, use the no form of this command.

snmp-server packetsize byte-count

no snmp-server packetsize

Syntax Description

byte-count

Integer from 484 to 8192. The default is 1500.

Command Default

Packet size is not configured.

Regards,

Sathvik K V

[daniel.dib]

That command sets the maximum size though. It doesn't say anything about minimum or average size.

Daniel Dib
CCIE #37149

[daniel.dib]

It depends on the bandwidth available in the network. Only once have I ran into SNMP putting stress on the network but that was a very low bandwidth network with 64 kbit/s links and so on.

Daniel Dib
CCIE #37149

[Richard Burts]

I agree with Daniel that rarely is the load imposed on the network by SNMP going to have noticeable impact. It is really not important what is the packet size and is more important how much information is being sent. And the major factor that determines this is how your NMS server is configured. Let us consider a somewhat extreme example in which the NMS is polling all devices every 10 seconds and is requesting all interface status, all memory status, contents of the entire routing table, and a copy of the configuration (all this information for every poll to every device every 10 seconds). If your NMS is configured in a more reasonable way then the load on the network will be reduced.

HTH

Rick

[Joseph W. Doherty]

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Posting

actually i want to enable SNMP for access switches about 100 unit. this is for NMS (non cisco). is it the SNMP packet will affect the network performance?

It might - it depends (i.e. how often you poll the device and what data you poll for).  (Also, SNMP polling can add to the device's CPU loading.)

[fazmibakar]

thank you for the replies. it give me ome ideas regarding the SNMP configuration.

[_|brt.drml|_]

A very late question.

If you do set the SNMP packet size?

Will you chop up the reply? So you generate a steady stream of reply and GET?

Or is it better to shape it with a QoS policy?