option hostname

Simon Hobson dhcp1 at thehobsons.co.uk
Fri Dec 19 10:03:02 UTC 2008

abhijit khadatare wrote:

>      i need to set up linux based isc-dhcp server gives ip based on 
>hostname only.

Search in the archives for Option 82, the process you'll need is very 
similar (but a bit messy).

>We have switch which insert its hostname in dhcp packet,
>so the scenerio is like this
>[switch_1]-------------------------[isc-dhcp server]------[switch_3]
>                                                     |
>                                           [switch_2]
>all client connected to switch_1 having hostname in their dhcp 
>packet get replaced by "switch_1"
>  since switch replaces hostname from client dhcp packet so there 
>might any problem occures?

Apart from all clients having the same hostname, so DNS updates will 
fail, and the server will try to give them the same IP address (but 
fail because there won't be a free lease).

>when we on debug mode msg . is "Unable to add forward map from 
>host_name.isc_dhcp to <> timed out"
>can any one suggest why this msg came?

Sorry, crystal ball isn't working at the moment, what does your config say ?
Also, learn how to turn off silly formatting mode (html) in your 
mailer, then it won't mangle :
>"Unable to add forward map from host_name.isc_dhcp to timed out"
>"Unable to add forward map from host_name.isc_dhcp to 
><> timed out"
If you can't see any difference in the two lines above, then it's 
also mangling what it shows you and you aren't seeing what everyone 
else does !

There are several reasons why the updates could fail. Is it trying 
the correct server (this is automagic if your DNS is configured 
correctly, or can be forced with s zone statement) ? Is the server 
configured to accept updates ? Is anything logged by your DNS server 
(this usually reveals the problem) ?

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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