[c-nsp] disabling dCEF per VIP on 7500? (fwd)

[Rafi Sadowksy]

## On 2004-08-13 08:21 +0300 Hank Nussbacher typed:

HN> 
HN> > A few years ago, some of our routers had VIP2-40s w/ only 32MB.  When they
HN> > ran out of DRAM (as soon as BGP got about halfway loaded), you'd get a
HN> > malloc failure in the syslog, but everything stayed up and it was relatively
HN> > benign.  These boxes had a mix of 40s and 50s.  dCEF would stay working on
HN> > the 50s and "sh cef linecard" displayed that the 40s were "disabled".
HN> 
HN> Exactly what happened to ours as well.  We had to upgrade the linecards
HN> from 128M to 256M in order to fix the problem.  'sho cef linecard' is your
HN> friend.   -Hank
HN> 
HN> > Am not positive, but when dCEF disables, router then defaults to what, fast
HN> > switching?  Some non-distributed CEF?  The load on the RSP was definitely
HN> > higher.  In fact, when all the 40s were replaced with 50s, there was a nice
HN> > drop in RSP CPU.
HN> >

 IIRC default config is punting from dCEF to CEF on the RSP
you may find "sh cef not-cef-switched" and "sh cef drop" useful to check
==
 Also you can see below dCEF completly frees the RP CPU 
(this is on a productions 7513)

 Each CYbus is carrying around 400 Mb/s and the RSP8 is almost 100% idle
(note that BGP table is small ~600 routes with 20 neighbors)

C7513 >sh contr cbus utilization

CY0Bus utilization for five seconds: 53%; one minute: 53%; five minutes: 53%
CY1Bus utilization for five seconds: 50%; one minute: 50%; five minutes: 50%


C7513>sh proc cpu s | exc 0.00%__0
CPU utilization for five seconds: 1%/0%; one minute: 0%; five minutes: 0%
 PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
 160     2915612    473791       6153  0.55%  0.06%  0.00%   0 BGP Scanner
  64     9064380 148095509         61  0.15%  0.07%  0.08%   0 IP Input
 156     9957124 127560525         78  0.07%  0.07%  0.07%   0 NTP
  54         536       554        967  0.07%  0.01%  0.01%   2 SSH Process


-- 
HTH,
	Rafi

P.S. when searching for dCEF related docs on CCO you way want to search
for "linecard" rather than "VIP" as of the GSR docs also 
apply(explicitly) to 75XX