[CentOS] DHCP static hosts and subnet configuration

Marcus Moeller mm at gcug.de
Sat Oct 18 07:59:09 UTC 2008

Dear John,
>> Subnet A (192.168.2.x) <-> DHCP Server with 2 NICs <-> Subnet B (
>> Clients on Subnet A should get a static IP from the host declaration.
>> Clients on Subnet B should obtain dynamic IP addresses from a range.
>> The two subnets are not physically connected but a CLIENT should be
>> able to connect to Subnet A or to Subnet B as well.

> This is what is confusing. If there *NOT* Physically Connected you will
> never CONNECT to them.

In this setup Subnet A is a private network and Subnet B is a network
for public Wifi access. If one got a notebook and his/her mac-address
is listed in Subnet A declaration he/she should be able to obtain an
IP. In some situations this machine may just want to access to public
wifi so he/she should also be able to connect to Subnet B as well.

ATM, the client will only get an IP address if there is a static host
declaration for it in both networks. Otherwise it would just be able
to connect to Subnet A and will never receive an IP from the dynamic
range of Subnet B.

In the near future Subnet A will be migrated to a Class A network, so
'subnetting' may be possible, but I don't think that this will change
the situation.

I also wonder if it's really necessary to run two instances of DHCP
with separate config files as dhcpd3 is able to detect the Subnets on
which it may deploy leases, depending on the NIC configuration.

Best Regards

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