A Question on Dynamic DHCP/DNS IP Lease Renew

David Li dlipubkey at gmail.com
Wed Sep 28 20:44:38 UTC 2016

We are using Dynamic DHCP/DNS with ISC DHCP and DNS server on Centos 7.
That is our DHCP server assigns an IP from a range based on the MAC address.
It will then update the DNS record with the IP and hostname.

For example:

Here are a few relevant lines from  /etc/dhcp/dhcpd.conf to assign IP
with hostname "node-1-1" to a server with MAC address

# Subnet and range
subnet netmask {

  option routers;


# host name and MAC
host node-1-1 {

  hardware ethernet   10:00:00:7a:a9:98;

  option host-name    "node-1-1";


This will result in a entry in the DNS entry like this:

node-1-1 A

TXT "003a7e20199e62a68504ff027bf35b1d78"

My question is: if the server is rebooted, will it come back and be
assigned the same IP again as long as its MAC stays the

I tested a few times and it seemed to be the case. Are there any
circumstances that a different IP will be assigned to the same server?



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