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

[Gert Doering]

Hi,

I've searched for a while in the documentation, but can't find anything
that does what I want - well, maybe it's not possible, but it's worth a
try asking here.

I have a 7507 with 12.0(27)S2 on it, and 5 VIPs in it.  Two are VIP2-50s
with 128Mb DRAM and "fastish" interfaces (POS-OC3, FE), the other 
three are VIP2-40's with 64 Mb DRAM and "slowish" interfaces (10Mbit 
Ethernet, 2Mbit G.703 or X.21).  

RSP4 with 256 Mb DRAM, full BGP tables.

Until recently, the box was running "plain CEF" (central CPU) and did
well.  Some CPU spikes here and there, but nothing critical, and no urgent
need to change anything.

Nevertheless I decided to go to distributed CEF, because it's supposed
to scale better in case of "many packets flowing" in parallel to "large
BGP updates".

Now the interesting part is: I want to have the box run dCEF on the 
VIP2-50s, but not on the VIP2-40s.

I know I can disable dCEF per-interface ("no ip route-cache distributed"),
but it's not disabling the actual FIB download onto the VIPs.

The VIP2-40s are very tight on memory right now:

VIP-Slot1>sh mem
               Head     Total(b)     Used(b)     Free(b)   Lowest(b) Largest(b)
Processor   60B57F20    55214304    53458740     1755564     1721604  1645500
      PCI   30000000     2097172     2041668       55504       55504    28468

... and I'm fairly sure that in a couple of months, their memory will
be full (this is with all interfaces on "no ip route-cache dist" already,
didn't make a difference in memory usage).

Documentation says something like "in that case, dCEF will just be 
disabled on the offending line card", but from experience, I assume that
it will result in funny things (CBUS complex, VIP2 restarts, or some
other nasty service interrupting surprise).  So I want to turn off 
dCEF for that whole line card *now*.

--> Is that possible?  Disable dCEF on one VIP purposely, and have it
running on the other ones?

gert

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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de