Router/DHCP is handing out .255 address

Answered Question
Oct 2nd, 2008
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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

Correct Answer by Richard Burts about 8 years 7 months ago

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

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Giuseppe Larosa Thu, 10/02/2008 - 10:52
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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

Correct Answer
Richard Burts Thu, 10/02/2008 - 11:13
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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

Richard Burts Fri, 10/03/2008 - 03:27
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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

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