Automatic Interface Shutdown in IOS XR

[Aleksandar Vidakovic]

• References

This document is an early notification of a behaviour change that will be introduced in IOS XR release 6.5.

IOS XR configuration principles relevant for this article are:

1. On router platforms all interfaces must be by default in shutdown state.
2. Only explicit configuration is permanent.

Due to principle #1, interface auto-shutdown is applied on interfaces without any configuration. However, due to principle #2, this auto-shutdown is not saved by the config manager. Otherwise the consistency of commit rollback may be disrupted.

This table illustrates the typical sequence of events that illustrates the difference between the old and new behaviour:

Actions	Result: Current (Old) Behaviour	Result: New Behaviour
New LC is inserted Every interface on the LC is in admin down due to auto-config User applies some configuration to any of these interface (for example interface description) Router or LC is reloaded	Interface is up after LC boot even if "no shut" was never configured	Interfaces remain down after LC boot. Explicit "shut / no shut" configuration is required to control the interface state.

Starting With IOS XR release 6.5.1, the main principles still remain. The auto-config is now saved into a file
named "<last_commit_ID+1>.snd_shut_<req-id>_<node-id>". Upon rollback this file is consulted and configuration is merged.

 References 

CSCvd14888: Interface shutdown config disappear after the router reload for CiscoXR running 6.1.2.