Subject: Re: [netatalk-admins] Why use small net ranges?
From: Bill Studenmund (skippy@macro.stanford.edu)
Date: Fri Oct 17 1997 - 12:50:26 EDT
On Fri, 17 Oct 1997, Patrik Schindler wrote:
> Hi, Bill,
>
> >Why do you have this setup? Do you really have 253*301 > 76,000
> >computers???
>
> Why should he not do this? I've here a netrange from 13-20 and only 5 Ethertalk devices. If there's no good reason (internic, government, top level admin or similar) for using as less as possible numbers, why may not everyone use as much as (s)he wants?
> I think it's is only a cosmetic question and in almost all cases not responsible for malfunctions.
I'm sorry. I meant to look up the multicast stuff last night, but forgot.
The main reason for keeping your net small is for kernel efficiency.
There's more overhead w/ more nets. Specifically the routing needs go up.
Also, I'm not sure if the multicasting needs go up (it's been a while
since I looked at that part of the code).
We've been at this thread so long, I've forgotten if this is Linux or BSD.
I know that the *BSD kernels use a tree, keyed on bits in the desired
node, to keep track of the routes. So for a range of 200-500, you'd have
the following routes:
200->207 8 nets
208->223 16
224->255 32
256->383 128
384->447 64
448->479 32
480->495 16
496->499 4
500->500 1
I don't see how that's nicer, if you don't have the computers to need the
space.
I'm not sure how Linux does it, but I've seen mention of "too many routes"
errors in Linux faq's, so I gather it's better to go sparingly with the
routes.
You're right that it will work with this large range, but I think the
general operation of things will be a little less efficient.
Take care,
Bill
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