[NTLUG:Discuss] IP super/sub-netting maddness

[Wayne Walker]

In theory, you could use 255.255.255.200 and 192.168.1.64.

BUT, why do you need to refer to those machines as a subnet?  For
firewall rules?

If so, just treat it as two 26 bit subnets.

192.168.1.64/26  255.255.255.192
192.168.1.128/26 255.255.255.192

Wayne

On Tue, Sep 19, 2006 at 02:18:06PM -0500, Richard Geoffrion wrote:
> Ok... I think I'm asking the impossible here because no matter how I 
> calculate it the bits don't line up...but here goes. 
> 
> Can you supernet multiple subnetted network ranges when they don't fall 
> on bit boundaries??
> 
> For instance, 
> 
> Networks 192.168.0.0 mask 255.255.255.0 and 192.168.1.0 mask 
> 255.255.255.0 can be referred to / supernetted  by changing the mask to 
> 255.255.254.0.  This gives 510 available hosts on the same network 
> instead of just 254.
> 
> 
> Now... what about a situation where I have a 125 ip address DHCP scope 
> on a 192.168.1.0/24 segment...and (in my infinite wisdom and foresight) 
> I started it at 60.  Yes... 60. Just pick a number...ANY number.  Throw 
> a dart -- WHOO HOO!  Triple 20!   The DHCP scope is 192.168.1.60-185.
> 
> Now that the DHCP scope is set.. let's put servers and other special 
> statics from 1-47 and printers from 224-254... YEAH!! Let's just trash 
> both /25 subnets with 'stuff' we can't move.
> 
> Now that we have all our static hosts and printers integrated... .how 
> about we firm up these ranges (which is where I got those numbers above) 
> and see if there is a way to reference the DHCP scope by network.  
> Hmmm... nope.. BUT.. if I modify the dhcp scope to 
> be...192.168.1.64-192....then the DHCP scope will fall on the ranges of 
> several subnets.
> 
> So...is it possible to supernet the subnets?  (I know it sounds 
> ridiculous...and unlikely...but if it's possible it would be a great 
> learning experience for me...not to mention making firewall rules 
> easier. :) )
> 
> Afterthought...  In the history of TCP/IP...has a subnet mask such 
> as........well...no...that'd be an invalid subnet mask.  hm... still... 
> has something like (11111111.11111111.11111111.1101xxxx) 255.255.255.200 
> ever been used?
> 
> -- 
> Richard
> Nope...I'm not smoking anything....
> (not to say I'm not crazy...just not smok'n)
> 
> 
> _______________________________________________
> http://www.ntlug.org/mailman/listinfo/discuss

-- 

Wayne Walker

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