multiple subnets
Simon Hobson
dhcp1 at thehobsons.co.uk
Wed Apr 2 15:10:16 UTC 2008
M U wrote:
>>>I'm using the ISC DHCP server V3.0.5 on Linux.
>>>I want to make the DHCP server work like below.
>>>
>>>1. One client(it behaves like a proxy) of 172.17.30.0/29 acess the
>>>DHCP server(172.17.101.1/24,ETH0)
>>>
>>>2.This client wants to get the ipaddress from DHCP server from the
>>>following range(10.30.0.1 10.30.255.254) to provide/distribute the
>>>ipaddress for the PC under this client.
>>>
>>>PC---+(172.17.30.0/29)proxy client ----> DHCP ser(172.17.101.1/24 ETH0)
>>> <--------------------------------
>>> 10.30.0.1 10.30.255.254
>>>
>>>
>>>Firstly, technically, is it possible to implement on the DHCP
>>>server like the above ?
>>>
>>>If possible, would you teach me how to configure or let me know
>>>the good free document or so ASAP ?
>>You need to make your proxy client a dhcp relay.
>>To do this, execute dhcrelay -i <interface facing clients> -i
>><interface facing server> <ip address of the dchp server>
>How should I configure the DHCP server ?
Step 1 - RTFM ! Start with the man pages for dhcpd, dhcpd-conf, and dhrelay.
Step 2 - if you still don't know, perhaps you could explain what you
want to achieve, because it's not clear from your question. The
reason for asking what you want to achieve, is that often people will
ask how to do a certain thing - when actually what they want isn't to
do that.
But a few pointers to get started with :
The simplest approach is that the relay agent should have an address
in the 10.30.0.0/16 subnet. It will probably work if it doesn't (ie
it only has an address in the 172.17.30.0/29 subnet), but then you
will need a shared network declaration.
You declare the 10.30.0.0/16 subnet, declare any subnet specific
options, and define a range of addresses to be given to clients. NB -
10.30.0.1 to 10.30.255.254 is not a practical range to be given out
(assuming a 16bit netmask as it leaves no usable address for a router.
Any ranges defined MUST contain only addresses which may be given out
to clients - ie addresses used by routers, statically defined clients
etc must NOT be included. This is different to the usual methodology
used when administering Windows DHCP servers.
You MUST declare a subnet for the 172.17.101.0/24 subnet but you do
not need to have any dynamically assigned ranges. The DHCP server
won't start otherwise.
You MUST have full routing between the 172.17.101.0/24 subnet and
10.30.0.0/16 subnet or the clients won't be able to renew their
leases.
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