I have a set of ec2 instances (ubuntu trusty 14.04) that I have never done any special dhcp configuration with. It's on a VPC with the default dhcp options.
For some reason, roughly ever 25 minutes, I see this in my logs
(IP's and xid are scrubbed)
DHCPREQUEST of 172.16.1.111 on eth0 to 172.16.0.1 port 67 (xid=0x0000000c) DHCPACK of 172.16.1.111 from 172.16.0.1 bound to 172.16.1.111 -- renewal in 1693 seconds.
(The exact number of seconds changes between 1300 and 1700.)
Occasionally, like once every 10 days, this renewal will break DNS, and my running application will start giving errors like
getaddrinfo: Name or service not known. Once the renewal runs again in about 25 minutes, the problem is resolved. I have tested this by waiting for a failure and manually renewing the dhclient lease (
sudo dhclient -v -r eth0 then
sudo dhclient -v eth0), and seeing that fix the issue instantly.
I have 2 questions:
Why is the renewal time this strange ~25 minute number? I know that I can set this through a conf file, but this seems like it's a strange default.
Why does it sometimes break DNS resolution? This is the main issue here. My other sets of ec2 instances also have this short DHCP renewal time, but only this one set of instances has the issue where, occasionally, DNS breaks when DHCP is renewed.