Ssh; Stateful Srp Switchover (High Availability) - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - RELEASE NOTES 2010-11-09 Release Note

SSH

Stateful SRP Switchover (High Availability)

Copyright © 2010, Juniper Networks, Inc.
If the SRP module restarts when SSH is configured in a VR other than default, SSH

can sometimes become disabled. This happens if SSH attempts to bind with a VR
before the VR comes back up after the restart. In this event, a warning message is
generated to alert you to the fact that SSH is disabled in that VR. You must manually
re-enable SSH either by accessing the console VTY or creating a Telnet session to
the router.
Additional processing is required to maintain and mirror the necessary state

information that enables subscriber sessions to stay up across an SRP failover. As a
result, the performance of other control plane functions is reduced. Specifically, call
setup rates are lower than in previous releases.
Informational Note:
Rapid call setup rates are most important following an outage
that causes all subscribers to drop, because many of the dropped subscribers will
immediately attempt to reconnect. This type of outage occurs far less frequently with
stateful SRP switchover.
We have ongoing development activities to characterize and improve call setup rates
in future releases.
Stateful SRP switchover remains inactive for 20 minutes after an initial cold-start or

cold-restart of the router. This delay enables the system to reach a stable
configuration before starting stateful SRP switchover.
If you want to override the 20-minute timer, turn high availability off by using the
mode file-system-synchronization command, and then on again by using the mode
high-availability command.
When IP tunnels are configured on a router enabled for stateful SRP switchover, and

the Service Module (SM) carrying these tunnels is reloaded, stateful SRP switchover
transitions to the pending state. Stateful SRP switchover remains in the pending
state for 10 minutes following the successful reloading of the SM. This amount of
time allows for IP tunnel relocation and for the tunnels to become operational again
on the SM. If an SRP switchover occurs while in the pending state, the router
performs a cold restart.
Work-around: None.
When you issue show commands as soon as the CLI is available after a stateful SRP

switchover, the commands can hang until the warm restart is completed.
After a stateful SRP switchover, each layer of the interface columns must

reconstruct its interfaces from the mirrored information. While the interfaces are
being reconstructed the SRP module cannot send or receive frames, including the
protocol frames that signal graceful restart behavior with OSPF and IS-IS peers. If
the configured hold time is too short, peers might mistakenly declare the adjacency
down during the time in which the graceful restart is taking place. [Defect ID 65132]
Work-around: Increase the hold time to provide sufficient time for interface
synchronization before the peers declare the adjacency down.
Release 11.3.0
Known Behavior 37