Cisco Cisco IOS Software Release 12.4(22)XR

Periodic accounting (not to be confused with the synchronization timer mentioned in the 

 section).

These timers are restarted on the standby when failover occurs, and the elapsed time is not synchronized 
to the standby. The effect will be to extend the timers beyond their original values by a time equal to the 
time that has already expired. This ensures that the user will not perceive a session failure on failover.

The following restrictions exist for the PDSN Session Redundancy Feature:

Limitation for Resource Revocation with SR Setup. 

Setting the revocation timestamp to “msec” (ip mobile foreign-service revocation timeout 5 
retransmit 4 timestamp msec) for PMIP flows with Session Redundancy is not permitted. 

The “msec” option puts the uptime in the timestamp field, and the uptime of the standby router is 
expected to be lower after switchover when the standby PDSN takes over as active (and when the 
PMIP flow was closed). Therefore, revocation on HA will be ignored because the identifier value in 
the revocation message is less than what is expected by HA.

The ip radius source interface command does not support virtual address (HSRP), and hence the 
IP address configured in Loopback interface to be used as source interface (NAS IP address) for 
reaching the AAA server in SR setup.

IP local pool recycle delay needs to be configured with a minimum delay of 30 (ip local pool 
pdsn-pool first_ip last_ip recycle delay 30). 

It is also advisable to have minimum of (calls per second * recycle delay) extra IPs than required as 
a buffer, so that sessions do not drop because of IP depletion.

The following sections identify information that is synchronized to the standby unit:

The control character mapping per used Asynchronous High-Level Data Link Control (AHDLC) channel 
is preserved. As the default is normally used, only those that are different are synchronized. The AHDLC 
channel number is not synchronized; an available channel will be selected independently on the standby.

The GRE Key is synchronized. The flags are synchronized as the sequence flag can be set on a per user 
basis.

The contents of the A11 messaging will be treated as described here.

Flags—Fixed and no synchronization is required.

Lifetime—Synchronized.

Home Address—No synchronization is required.

HA—No synchronization is required. This is the HSRP address of the R-P interface. This is used 
for proposing a PDSN IP address when clustering is configured. This will be the HSRP address of 
the proposed PDSN. It is only used prior to session establishment.

Care-of-Address—Synchronized. This is the PCF IP address for the R-P Session.