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

[joseph beasley]

Don't mean to be pushy....   but here goes...

Odd and invalid.  Here are a few links.

http://www.freesoft.org/CIE/Course/Subnet/6.htm

http://www.pku.edu.cn/academic/research/computer-center/tc/html/TC0306.html

http://www.exabyte.net/lambert/subnet/subnet_masking_summary.htm

http://freespace.virgin.net/glynn.etherington/subnet_masks_and_ip_for_beginners.htm

--- Kenneth Loafman <kenneth at loafman.com> wrote:

> Just a nit, but it is odd, not invalid...
> 
> 255.255.255.200 == FFFFFFC8 or 1..11001000
> 
> which means you have 5 bits to play with, just not an adjacent 5
> bits,
> thus there are 32 possible IPs in the subnet, C8-CF, D8-DF, E8-EF,
> and
> F8-FF.  This fits the def of a submask, but would not be compatible
> with
> CIDR notation except as 4 distinct small subnets of 8 each.
> 
> I've seen this used for device subnets where redundant devices are
> subnetted.  Not spiffy, but valid.
> 
> ...Ken
> 
> joseph beasley wrote:
> > 255.255.255.200 is not a valid subnet mask.  255.255.255.192 or
> > 255.255.255.224.  Just follow the bits.
> > 
> > --- Wayne Walker <wwalker at bybent.com> wrote:
> > 
> >> 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
> >>
> >> www.unwiredbuyer.com - when you just can't be by the computer
> >>
> >> wwalker at bybent.com                    Do you use Linux?!
> >> http://www.bybent.com                 Get Counted! 
> >> http://counter.li.org/
> >> Perl - http://www.perl.org/           Perl User Groups -
> >> http://www.pm.org/
> >> Jabber:  wwalker at jabber.gnumber.com   AIM:     lwwalkerbybent
> >> IRC:     wwalker on freenode.net
> >>
> >> _______________________________________________
> >> http://www.ntlug.org/mailman/listinfo/discuss
> >>
> > 
> > 
> > Joe Beasley
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> 


Joe Beasley
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