Solved: Router/DHCP is handing out .255 address

nygenxny123 · ‎10-02-2008

This is our current configuration for our dhcp server/router.

ip dhcp pool ncore-pool

network 192.168.134.0 255.255.254.0

default-router 192.168.134.1

As you can see we are using a .254 subnet mask

However, one host was getting

192.168.134.255 as an assigned IP address.

Being that we are using a /23 mask. Wouldnt the host still be able to connect

to our network, as .255 is no longer

the broadcast address of the subnet?

she was unable to until i excluded

192.168.134.255 from the dhcp and

she was given another ip address

Richard Burts · ‎10-02-2008

Richard

From the perspective of the Cisco router using 192.168.134.0 with a /23 mask if legitimate and the user should have been able to connect and to access resources. But there are some devices (some OSes - and I think that it includes at least some versions of Windows) that see 192.168.x.x and automatically treat it as a /24 and do not recognize the supernet that you are attempting to use.

HTH

Rick

HTH

Rick

View solution in original post

Giuseppe Larosa · ‎10-02-2008

Hello Richard,

for network 192.168.134.0 255.255.254.0

the IP directed broadcast is:

192.168.135.255

/23 the ip directed broadcast address is the one with all 1 in the host portion

some other device was treating this address as an IP directed broadcast check on all devices in the path

What routing protocol are you using ?

Hope to help

Giuseppe

Richard Burts · ‎10-02-2008

Richard

From the perspective of the Cisco router using 192.168.134.0 with a /23 mask if legitimate and the user should have been able to connect and to access resources. But there are some devices (some OSes - and I think that it includes at least some versions of Windows) that see 192.168.x.x and automatically treat it as a /24 and do not recognize the supernet that you are attempting to use.

HTH

Rick

HTH

Rick

nygenxny123 · ‎10-02-2008

thx!

Richard Burts · ‎10-03-2008

Richard

I am glad that my response helped to resolve your question. Thank you for using the rating system to indicate that your question was resolved (and thanks for the rating). It makes the forum more useful when people can read a question and can know that there was a response that did resolve the question.

The forum is an excellent place to learn about Cisco networking. I encourage you to continue your participation in the forum.

HTH

Rick

HTH

Rick