Compatibility problem PFC3CXL and DFC3C

[connect101]

Dear all,
We are facing a problem installing a WS-X6724-SFP with DFC3C on a 7606-s / RSP720-GE with
DFC3CXL, once the interface module is inserted it is immediately powered down by the router.
And we get the following warning message.
Module 2 DFC installed is incompatible with system operating mode. Power denied.
To enable Module 2 DFC, the system must be reset.
WARNING: Any system reset will change the system operating mode which can result
in degradation of system performance. To eliminate this from occurring,
remove Module 2 DFC or replace with a system compatible DFC.

We tried to reset the entire system and the specific slot without success.
We are using the IOS : c7600rsp72043-advipservicesk9-mz.12.2-33.SRD4

Does someone has already faced this problem ?
Any help is welcome.
Thanks in advance.

Regards.

[Giuseppe Larosa · Accepted solution]

Hello Connect101,

I strongly recommend you to get a DFC 3CXL for the new linecard.

We had very bad experiences with SUP720 3CXL:

the linecard was accepted but the DFC was not able to store the whole CEF table

as a result of this the system started to process switch part of traffic and then cpu went to 100% making the system not usable

probably for this reason in later codes and with newer supervisor RSP720 there is a check that does not allow to introduce a linecard with an inferior DFC on board.

the system is probably working in DFC3CXL mode and this can be a setting that is a default or has been set on the router

if it is not a default if you make show run | inc dfc you should find a command setting the switching mode

However, as stated above if the system is used for receiving BGP full tables that are in the order of more then 300,000 prefixes a DFC 3C is not enough to handle them and would cause serious issues.

if the system is not used for receiving one or more BGP full table you could try to see if it is possible to lower the switching mode but you need also a command for that it is not enough to reload the chassis

Hope to help

Giuseppe