Network Management

SNMP discovery with @ postfix after community string in Orion Platform

When performing discovery, there are SNMP authentication traps or failures that indicates that Orion is trying to communicate with the SNMP Agent using @ postfix after the SNMP community strings. This behavior is also observed during standard UDT polling. This article addresses it.

First published date

11/2/2018 2:15 AM

Last published date

8/3/2022 9:42 AM

Overview

This article explains authentication errors where the community string is appending with @ at the end of the string when performing network discovery. For example, public@1.

Product section

Network Performance Monitor

Cause

N/A

Resolution

  • This behavior is expected as designed by Cisco and no changes are required to be performed.
  • Bridge MIB was designed with no support for VLANs, thus it is just a table of records without a column such as VLAN ID.
  • As a workaround, Cisco invented a technique that allows you to pass the additional context information to the agent by appending @context to the community string.
  • This is used to pass VLAN ID, so the agent is able to return VLAN-specific information that is held within the Bridge MIB.
  • Topology in Orion uses two versions of pollers: One which appends @VLANID at the back of the community string, and another which does not.
  • During discovery, Orion first tries to use the @VLANID postfix and if it fails, it will fall back to using the poller without the @VLANID.
  • During standard UDT polling, UDT polls the same MIBs as above and it is common to see the same behavior as during the discovery.