[c-nsp] Problem faced on E1-IMA cards

[Malik Naeem]

Hi

I am using Cisco 7206 VXR as Broadband Remote Access Server for the
termination of PPPoE sessions primarily. The IOS version is 12.2(15)T8
and the following modules are installed on it:

	Slot # 1: PA-A3-T3 (DS-3 port adapter)
	Slot # 2: PA-A3-OC3MM (OC-3 port adapter)
	Slot # 3: PA-IMA-E1 (8 port E1-IMA port adapter)
	Slot # 4: PA-IMA-E1 (8 port E1-IMA port adapter)
	Slot # 5: PA-8E1/120 (8 port Channelized E1 port adapter)
	Slot # 6: PA-MCX-8TE1

Out of the above modules installed, there is no traffic/load on the
OC-3(slot#2) and channelized E1 adapters(slot#6). I am facing problems
on the E1-IMA cards.

The E1-IMA card on slot#3 has 2 ima-groups (each IMA contains 2 E1s) and
from the rest of the ports two are occupied and and one is free. The
number of sub-interfaces on each IMA group is around 200 (one
sub-interface for each subscriber). Among the rest of the interfaces,
two interfaces have around 70 sub-interfaces each and one has 24
sub-interfaces. So, the total number of sub-interfaces on this slot is
approximately 600. The total number of sub-interfaces on Slot#4 is
approximately 300 (with two IMA-Groups each containing 2 E-1s and two
interfaces free).

We are facing a very strange problem that ATM interfaces on E1-IMA slots
start misbehaving without any particular interval. The ping response
gets very slow with almost 100% packet loss. We need to refresh all
interfaces on that particular Slot (including IMA-groups). After
refreshing, everything gets fine immediately. Sometimes this problem
gets so swear we need to reset the card by taking it out and then
re-inserting it solves the problem. This problem occurs more frequently
on the interface with less number of sub-interfaces (i.e.less load).

During such periods the CPU load is quite normal and there is no
indication which shows the reason for such behavior. The maximum number
of PPPoE sessions during peak times is around 450. Such mis-behavior has
no specific time, it even occurs when the traffic is least i.e. when
minimum number of users are connected.

Any suggestion would be highly appreciated.

Regards

--
Naeem-ud-Din
Operations Engineer
Dancom OnLine Services
Islamabad, Pakistan