DHCP configuration on RHEL6

Hua Zhong Wang wanghuaz at cn.ibm.com
Wed Apr 13 16:28:58 UTC 2011


We are working on a solution to manage large clusters, there will be
thousands of clients requesting dynamic IP address from dhcp server, and on
each client, there are several services that are working and heavily
depending on the dynamic ips.

We know that the dynamic ip addesses on each client generally will not be
changed, except the client is down for a long time and dhcp server re-use
the expired leases.

But once this happens, it will take lots of effort to reconfigure the
client based on the dynamic ip on the client.

So we are trying to find a way to gurantee the ip address on clients will
never be changed. Static ip address with a host declaration in lease file
or dhcpd.conf could help it. But this way needs us to firstly assign a
dynamic ip to the clients, and commnunite with the clients to get their mac
addresses, then write a host declaration with a new ip/mac into lease file
or dhcpd.conf.  And with this  configuration, properly we need to prepare
two ips to each client, one ip range for dynamic ips and another ip for
static.  Also it needs the clients to reset their adapters to switch from
dynamic ips to static ips.

This procedure is a little complicated expecially for managing a large
cluster, we are trying to simplify it, one proposal would be just to write
the dynamic ip that is inside the dynamic range into the lease file or
dhcpd.conf with a host declaration, to make the dynamic range to be static.
Several benifits: it doesn't need two ips per client, doesn't need to
assign new static ip by admin manually, and don't need to reset client's
adapters.  We got some message that dhcp server doesn't like users to do
so, so I would know the answer to the following question:

What exactly will happen if we put the dynamic ip which is in a dynamic ip
range to be static with fixed-address?  Is this way acceptable by dhcp
server and stable enough?

Best Regards,

Wang Huazhong(王华忠)

IBM CSTL HPC System Management Development
Tel: 86-10-82452279
Email: wanghuaz at cn.ibm.com
Address: Ring Building 28,ZhongGuanCun Software Park,No.8 Dong Bei Wang
West Road, Haidian District Beijing P.R.China 100193
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