From: CKORENT@xxxxxxxxxxxxx
Date: Thu Sep 14 2000 - 12:43:09 GMT-3
The use of access-lists IS supported with fast-switching (at least with newer
IOS). Here's a good link that briefly explains the different switching methods
:
http://www.cisco.com/warp/public/63/tuning.html
One place to disable fast-switching is on slow links (64k and below). This
slows down packet processing
through the router which helps reduce the effect of switching from a
higher-speed interface (like ethernet) to
a slower-speed link (a form of buffering).
I remember something about disabling fast-switching on dial-backup interfaces
also. This has something to
do with the router continuing to use the dial-backup link even if the primary
becomes available again
because the dial-backup path is in the route-cache. This fixes itself after th
e
route-cache gets invalidated.
This may not be needed in newer versions of code.
Chris
Kevin Baumgartner <kbaumgar@cisco.com> on 09/13/2000 08:44:33 PM
Please respond to Kevin Baumgartner <kbaumgar@cisco.com>
To: "Price, Jamie" <jprice@isgteam.com>
cc: ccielab@groupstudy.com (bcc: Chris A Korent/USA/Pillsbury)
Subject: Re: ip route-cache
All this does is to allow enabling of fast switch
or by doing "no ip route-cache" to disable fast switch and
doing process switching.
The issue is that some features will not allow fast switching.
For example access-lists. The router need to look into each packet
to see if there is match on the access-list. So in this case fast switching
can't be used.
With fast switching it looks at the first packet and then
finds out what interface to send it to. Then all other packets who destination
is the same address will be fast switched out to the same interface and
will no have to look in the packet at all. This is much faster than
process switching.
Also a quick troubleshooting thing to try if
packets are not going out a interface is to turn
off fast switching. Especially if you are try some new
features and then don't work.
Kevin
At 08:05 PM 9/13/00 -0500, you wrote:
>Hi,
>
>Can anyone help me out here?
>
>I've been wondering about the aforementioned command. I realize, after lookin
g
at the docs that "ip route-cache" enables fast switch processing but I'm curiou
s
about the parameters and the ability to disable it.
>
>Can anyone provide me with some solid, factual, reasons as to why you would
want to turn fast switching off or turn autonomous switching on, etc? Also why
can you use it on a Vlan interface in a switch - this one sort of has me at the
moment?
>
>If this is something basic that I'm overlooking.......well....I was going to
apologize but we all have to take a trip back to the basics sometime dont
we.....so I wont :)
>
>Thanks
>
>Jamie
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