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From Simon Waterhouse <>
Subject Problem with DHCP leases
Date Tue, 18 Feb 2014 16:49:17 GMT
I am having a few problems with DHCP leases from Virtual Router (CloudStack 4.2 / Basic Zone
/ XenServer) and wondered if this is a known problem.

Under normal circumstances everything is working fine, but occasionally  a running instance
does not get its assigned IP address via DHCP: tcpdump tells me the new instance is issuing
a DHCPDISCOVER and getting no response. Looking at the Dnsmasq logs on the VR it seems that
the DHCP server is declining to respond to the DHCPDISCOVER because the configured IP address
is leased to another MAC (this MAC is associated with the NIC of a long-since-dead instance).
Flushing the cache of existing leases in Dnsmasq by restarting the service seems to fix the
problem (for some definition of "fix").

As Dnsmasq appears to be configured in /etc/dhcphosts.txt to issue infinite leases can someone
tell me how leases get cleaned up if there is an abnormal termination of an instance such
that it cannot send a DHCPRELEASE on shutdown?


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