[nsp] diagnosing dCEF

[Matt Ploessel]

  If you're running into problems where some packets aren't making it
through, regardless of protocol, and they all seem to be about 92 bytes,
you might talk to Cisco about it. ;) 

-Matt Ploessel

>See http://www.cisco.com/warp/public/707/cisco-sn-20030820-nachi.shtml
>>
>>The policy-routing solutions works great in small routers (26xx, 17xx)

>>and in 7200s. In 7500s it seems OK *UNLESS* dCEF is enabled, then it 
>>does what you saw. I'm assuming it's dropping 92-byte TCP packets as 
>>well as the ICMP echoes. You can see 1-packet flows of mail getting 
>>dropped.
>>
>>Notice that the workaround cannot be used on GSRs because it causes 
>>packets to be punted to the CPU... this is as bad a news as that it 
>>doesn't work right on dCEF because we use GSRs or 7500s with dCEF 
>>where the network is really busy.




> -----Original Message-----
> From: Michael Loftis [mailto:mloftis at wgops.com]
> Sent: Thursday, August 28, 2003 6:06 PM
> To: Kenny Stoltz; cisco-nsp at puck.nether.net
> Subject: Re: [nsp] diagnosing dCEF
> 
> 
> RTFM mostly......There are a number of limitations for CEF, plus on a
> distributed platform you have to act it on the sup as well as the 
> linecards, and possibly interfaces.  If you want to privately send me 
> onfigs (minus password/snmp community/etc statements please, 
> I don't even 
> want to get itno that possibility, and any anonymizing you 
> feel necessary) 
> I'll take a look and see if I can make some suggesstions.
> 
> --On Thursday, August 28, 2003 19:55 -0400 Kenny Stoltz
> <kenny at qx.net> 
> wrote:
> 
> > I have a 7500 that has "ip cef distributed" enabled, and
> even though
> > this is turned on show interfaces switching produces output like
> >
> > FastEthernet0/0/0 to MilkyWay Port F0/11
> >           Throttle count         23
> >         Drops         RP        242         SP          0
> >   SPD Flushes       Fast        246        SSE          0
> >   SPD Aggress       Fast          0
> >  SPD Priority     Inputs       4319      Drops          0
> >
> >      Protocol       Path    Pkts In   Chars In   Pkts Out  Chars Out
> >         Other    Process    1451192  163629338    3011580  180694800
> >             Cache misses          0
> >                     Fast          0          0          0          0
> >                Auton/SSE          0          0          0          0
> >            IP    Process  128741017 2182744165  179065024 3715162917
> >             Cache misses         44
> >                     Fast 3850192978 4238328313 4230800234 4157756173
> >                Auton/SSE          0          0          0          0
> >       DEC MOP    Process          0          0      50103    3857931
> >             Cache misses          0
> >                     Fast          0          0          0          0
> >                Auton/SSE          0          0          0          0
> >           ARP    Process   78977079  443698726    1396932   83815920
> >             Cache misses          0
> >                     Fast          0          0          0          0
> >                Auton/SSE          0          0          0          0
> >           CDP    Process     503521  194990679     502129  159675732
> >             Cache misses          0
> >                     Fast          0          0          0          0
> >                Auton/SSE          0          0          0          0
> >
> > What is the easiest way to diagnose why dCEF isn't switching any
> > packets and IP Process is switching such a massive amount 
> of packets?
> >
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> 
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