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Date:      Wed, 28 Aug 1996 08:15:47 -0500 (CDT)
From:      ptroot@uswest.com (Paul T. Root)
To:        nickliu@netcom.com
Cc:        questions@freebsd.org
Subject:   Re: "Re: UTP to UTP Networking'"
Message-ID:  <199608281315.IAA20460@astro.acs.uswest.com>
In-Reply-To: <199608272038.PAA13185@horton.iaces.com> from "The Filter of proot@horton.iaces.com" at Aug 27, 96 03:38:24 pm

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In a previous message, The Filter of proot@horton.iaces.com said:
> 
>  > Your netmasks don't match your broadcast, and your broadcast should
>  > actually go to a subnet not a node.
>  > I'd do something like
>  > 
>  > ifconfig ed0 192.168.253.x broadcast 192.168.253.11 netmask 0xfffffffc
>  > 
>  > Broadcast will be automatically set via the netmask.
>  > 
>  > Paul.
>  > 
>  > 
>  
>  I know someone wise enough will stand up and be willing to teach me 
>  something.  Thanks, Paul.  
>  
>  In the address above, the broadcast address was set to 192.168.253.11, 
>  why 11 and not 10?  In lp0 (laplink interface), I do:

This is how subnetting works. I set the netmask to 255.255.255.252 ok. 
That leaves you 2 bits for your sub net. Your addresses are
9	- 00001001
10	- 00001010

and we'll throw in 8 and 11:
8	- 00001000
11	- 00001011

then the netmask 252
252	- 11111100

So with a 2 bit subnet you get 00, 01, 10 and 11. You generally don't
use 00, and 11 is broadcast (that's the same as 255 in an 8 bit subnet). 
So a broadcast wants to go to the broadcast subnet. 

252 is the subnet we use to put together point to point and Frame Relay
links.

>  ifconfig lp0 192.168.253.7 192.168.253.8
>  route add ...
>  
>  and
>  
>  ifconfig lp0 192.168.253.8 192.168.253.7
>  route add ...
>  
>  And it worked fine.  I know it would be just a simple knock-on-the-forehead 
>  hint to make me understand all that.  
>  
>  Please give me a punch instead of a knock.  Thanks.
>  
> 
> -- End of filtered message --
> 


-- 
Paul T. Root - USWEST !NTERPRISE Networking Service	ptroot@uswest.com

"Your friend dissected, yourself a mental vegetable; not a pleasant
prospect, is it, Captain?" -- Kang



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