Cisco ASR 9000 IOS XR Show Commands: IM, SYSDB and uIDB

2026年9月2日 LOG admin

When a Cisco ASR 9000 router running IOS XR misbehaves - interfaces stuck in the wrong state, sysDB verification failures, or memory alarms - the first escalation step is a family of support-level show commands that inspect the interface manager (IM), the system database (SYSDB), the micro-interface descriptor blocks (uIDB) and the watchdog thresholds. This article walks through the Advanced System Command Reference chapter on troubleshooting commands and explains what each command actually shows.

show im database - Interface Manager State

RP/0/RSP0/CPU0:router# show im database verbose interface null 0

The interface manager (IM) is the IOS XR process that owns interface state. show im database dumps what IM believes about an interface - flags, MTU, encapsulation, owner views, state transitions and checkpoint data. Options like brief, summary, ifhandle and view filter the database, and every query takes a location argument in rack/slot/module notation because IM runs per-node.

show imds interface brief - Distribution Checks

RP/0/RSP0/CPU0:router# show imds interface brief location 0/0/CPU0

IMDS is the interface manager distribution server. The brief output shows interface state, encapsulation, MTU and the ifhandle for every interface, which makes it fast to spot an interface whose state or MTU is not what the config says it should be.

show sysdb connections and Verification Traces

RP/0/RSP0/CPU0:router# show sysdb connections
RP/0/RSP0/CPU0:router# show sysdb trace verification location 0/RP0/CPU0

SYSDB is the configuration and operational database at the heart of IOS XR. show sysdb connections lists which processes hold client connections to the database, while the trace verification commands display recent database transactions and confirm whether configuration changes were verified and accepted on the local or shared plane.

show uidb data and show uidb index

Every IOS XR interface is represented by a micro-interface descriptor block (uIDB). When interface resources run out or handles look corrupt, these commands show the index data (show uidb data), the trace log of uIDB events (show uidb trace) and the handle-to-interface mapping (show uidb index) per location. uIDB exhaustion is a classic root cause of "interface created but never comes up" on large routers.

watchdog threshold memory

RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# watchdog threshold memory location 0/RP0/CPU0 minor 30 severe 20 critical 10

Watchdog alarms fire when memory availability drops below the minor/severe/critical percentages (defaults 20/10/5). The example above raises the thresholds on the RP to catch memory pressure earlier. Use show watchdog and show memory summary to correlate the configured thresholds with live memory usage.

Caution on Support Commands

Commands in this module carry the cisco-support task ID and are normally used with Cisco TAC: several can affect performance or system behavior if misused. Run them read-only first and check task-group permissions with your AAA administrator before changing anything.