The goal of this page is to document little tips or tricks for working with UEC that don't fit other places.

Multiple DHCP Servers / MAC Filtering

The installation of a CloudController adds a dhcp server to the network. It is managed and will only respond to instances. However, if you have another dhcp server on your same network, it may also respond, which could wreak havoc.

Eucalyptus creates its instances with MAC addresses starting with d0:0d. This means that you can configure the other dhcp server on the network to ignore instance requests by filtering on that MAC address.

This can be accomplished in in various dhcp servers:

dnsmasq

dnsmasq, which is used by dd-wrt or other wrt projects, just need to have the following to the config added:

dhcp-host=d0:0d:*:*:*:*,ignore

dhcp3-server

You configuration need to define a class matching the Mac address prefix, then exclude the class from a pool. Example /etc/dhcpd.conf:

#this class prevents serving request from instances
class "ignoreclass" {
    match if (substring(hardware,1,2)=d0:0d);
}

subnet 192.168.0.0 netmask 255.255.255.0 {
    option domain-name-servers 192.168.0.1;
    #other options here
    pool{ 
        #this is where we deny attributing addresses
        deny members of "ignoreclass";
        #all other mac addresses will receive addresses from this range
        range 10.0.3.101 10.0.3.199;
    }
}