IP Filters? (fwd)

MegaZone (megazone@livingston.com)
Wed, 9 Jul 1997 02:51:36 -0700 (PDT)

Once upon a time Fernando da Silveira Montenegro shaped the electrons to say...
>What seems to be the general consensus on how many filtering rules one can
>configure on a PM2-30 without imposing a noticeable performance penalty
>for the dialup users: 10? 50? 100?

No way to say - it only slows things down when you need to go deep into a
filter, since it stops checking at the first match.

I could have 1000 lines, but if the packets never went past the 10th rule
the speed is the same as a 10 line filter. This is why ordering does matter
a GREAT deal. Also, a well ordered filter can have fewer rules. You may
be able to group multiple permit or deny rules into one block and make it
shorter.

>I know that using, for instance, an outbound ethernet filter is more
>efficient than many inbound serial ones, but then I leave users able to
>telnet to my PMs, and that's a no-no.

Why not use a combination - basic filters on the serial ports to block ports
like telnet, and then in and out filters on the ether to take care of that
side too?

-MZ

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