A question about SNMP Configuration

[Mitrixsen]

Hello, everyone!

I have a few questions in regards to basic SNMP configuration commands on Cisco IOS. So if I understand this correctly, the moment I issue the snmp-server community text ro/rw command, I'll be able to retrieve information from this device and also SET specific configuration parameters on it? Because I originally thought you also have to issue the snmp-server host x.x.x.x command. 

I've also issued the following commands to configure SNMPv2 on a router.

snmp-server community 123 RO
snmp-server community 1234 RW
snmp-server host 192.168.170.13 version 2c 123
snmp-server host 192.168.170.13 version 2c 1234

I've specified version 2c yet I can still manage the device using a simple SNMP application even when I set the version on it to 1. How?

Thank you in advance for your help.

Kind regards,
David

[M02@rt37]

Hello @Mitrixsen,

You're rigth.

the snmp-szrver community command with the ro/rw option allows you to control the level of access for SNMP managers using that particular community string. SNMP managers using the community string set as read-write have the ability to both retrieve information and modify specific configurations on the device using SNMP SET requests.

On the other hand, snmp-server host a.b.c.d command is used to specify the SNMP managers that are allowed to communicate with the device using SNMP. It defines the hosts that can send SNMP queries or receive SNMP traps from the device.

Do you ensure that the SNMP manager is configured to use SNMPv2c explicitly ? If an SNMP manager supports both SNMPv1 and SNMPv2c and you've configured SNMPv2c in your device, the SNMP manager can use either version based on its configuration or capabilities. If the manager is configured to use SNMPv1, it can still manage the device even though you've specified SNMPv2c in the device configuration.

[Joseph W. Doherty]

"I've specified version 2c yet I can still manage the device using a simple SNMP application even when I set the version on it to 1. How?"

Not 100% sure without reviewing SNMP different version features but in general (for version variants of many things) often backward compatibly is supported across versions.  I.e. given version 2x and version 1x, the 2x version can likely can work with the 1x version by not using 2x specific feature, but, of course, 1x would not be able to communicate/support 2x features.