Question

A service provider NOC monitors an IOS XR router using SNMPv3 with authPriv. After the router's chassis is RMA'd and replaced, the monitoring server can no longer poll the device even though the SNMPv3 username, authentication password, and privacy password on the server are unchanged and match the router's configuration. The router shows the v3 user is still configured. What is the most likely cause of the authentication failure?

Accepted Answer

The router's SNMP engineID changed with the new chassis, invalidating the localized authentication and privacy keys cached on the NMS

Answer

SNMPv3 authPriv requires the community string to be reconfigured after any hardware replacement

Answer

The new chassis defaults to SNMPv2c, which cannot interoperate with an SNMPv3 authPriv NMS

Answer

The privacy protocol automatically downgrades from AES to DES on a replacement chassis, causing a cipher mismatch