Cisco Router – Random Cell Delineation Messages cause IMA connections to bounce

 For new IMA installs, cell delineation can initially appear to be a telco issue.  However, Cisco has identified a bug that can cause the ATM interfaces to drop and show cell delineation messages in the log.  Regardless of the telco line status.


The fix for this is to upgrade to 12.4(20)T2 or higher.  If trouble continues normal line troubleshooting should be performed.



Resolved Caveats—Cisco IOS Release 12.4(20)

Cisco Bug Details:



Symptoms: The show logging command displays messages such as the following:

<date>: %ATM_AIM-5-CELL_ALARM_UP: Interface ATM<if ID> lost cell delineation. <date>:

%ATM_AIM-5-CELL_ALARM_DOWN: Interface ATM<if ID> regained cell delineation.

The link may go down and then recover automatically.

Conditions: This symptom is observed under ordinary operation. There is no apparent trigger. The physical line is known to be good.

Workaround: There is no workaround.




FYI - Cisco IMA commands


Show IMA interface : brief description of all IMA links and their up/down status


Show controllers t1 : shows error stats for T1 links