Problems getting Cisco router and Motorola Nextlevel system to work together

I am having some difficulties involving using a Cisco 7200 router to terminate
ATM sessions from a motorola nextlevel IPTV system.

  The router is currently configured to use IRB which is a hybrid process.
The problems is that the IRB process is overloaded and is dropping traffic
faster than it can process it. I opened a case with Cisco TAC, and they
recommended using RBE instead of IRB.

  While I have been trying to plan migrating the system to RBE I discovered
that Motorola uses a concept called "dynamic pvc's" to assign the pvc's to
the CPE devices (a IPTV unit that has a data port). The device uses two
PVC's one for data and one for IPTV. The system dynamically assigns the PVCs
when the CPE devices connects. This looks like it would not work with RBE,
since the pvc can change before the dhcp lease expires.

  Having this router dropping traffic, has been causing severe problems for
end users and is causing an ongoing system outage. I am currently trying to
work with both Motorola and Cisco, however both vendors are blaming the
problem on the other vendor.

  I am not sure what to do. Motorola says their system only works with IRB
and Cisco says the router will not function with this size network using IRB.
Has anyone else arrived at a working solution using a Cisco 7200 router to
terminate a Motorola nextlevel system support approximately 2000-3000 end

  I would be extremely gratefull if anyone who has worked with this type of
system could help shed some light on this problem. Thank you in advance.

  The router is currently configured to use IRB which is a
hybrid process.
The problems is that the IRB process is overloaded and is
dropping traffic faster than it can process it.

Which NPE is in this router?

Basically, the 7200 has underpowered CPUs and if you force it to process
switch, then it handles a LOT LESS packets per second than you might
think. I expect that your config is forcing process switching rather
than fast switching.

The only three solutions are

A) run less traffic through the 7200 so that process switching can cope

B) stop using the feature that forces process switching

C) replace the 7200 with a 7300 which will probably not have CPU issues.
However, not knowing the specifics of what IRB is doing, I would advise
you to test a replacement platform before committing to it.

Oh well, maybe 4 solutions. If you are using a weak NPE such as NPE-200
you may be able to get some joy by upgrading to a more powerful one. For
instance an NPE-400 should handle roughly twice the load of an NPE-200.

--Michael Dillon

We should probably move this over to cisco-nsp.

I'd be interested to see a 'sh buffers' because if it's
process switching that much data I bet the buffers are thrashing.

I seem to remember working on something very similar to that
4 or 5 years ago when a customer has brigding over a bunch of
ATM PVC's and they told me it was some type of IPTV set top box.

We tuned the buffers really high so they didn't trim back and
it worked.

We also do some bridging under interrupt without process
switching too last time I checked so some more data would
be helpful.

Move it over to and we can help
more on the Cisco side if you want.


This router has a G-1 engine with 512 DRAM. I would stop using IRB, but it
appears that the way that motorola has implemented pvc's is very difficult to
work around. The Molorola middleware is dynamically assigning the pvc.
Yes... I have personly seen a CPE device change their vci after a period of
time. The device did not change ports or anything else but was provisioned
to a different vci after just sitting there. Thanks for the suggestions so

The buffers are overloading and dropping traffic. With a Cisco TAC case, the
tech had me increase the buffers so much it wasn't even funny. The only
problem was about and hour after we tried to tune the buffers, things got
very bad and I had clear them to default to stop a very ugly bigger outage.
This system does indeed involve IPTV set top boxes. I am unable to use RBE
since the PVC provisioning may change on the units and the VC would not match
what the dhcp lease was originally on. The way that this Motorola system
implements PVCs baffles me, it does not make any sense to me. They are
dynamically changing the vci assigning it out of a pool, just like DHCP does
with IPs. The circuits are not SVCs and the endpoint router is seeing things
change so this is not SPVCs either. I am trying to think of a way the change
this to work with RBE switching, but the dynamic PVCs are throwing a monkey
wrench into things. Thank for the help.