The ucast directive configures Heartbeat[1] to communicate over a UDP[2] unicast[3] communications link. The udpport[4] directive is used to configure which port is used for these unicast communications if the udpport directive is specified before the ucast directive, otherwise the default port will be used.
The general syntax of a ucast directive is:
ucast dev peer-ip-address
Where dev is the device to use when talking to the peer, and peer-ip-address is the IP address we will send packets to.
Although this is a unicast communication link, the UDP packets sent over this link is a multicast[5] protocol.
A sample ucast directive is shown below:
ucast eth0 10.10.10.133
This directive will cause us to send packets to 10.10.10.133 over interface eth0.
Note that ucast directives which go to the local machine are effectively ignored. This allows the ha.cf[6] directives on all machines to be identical.
| [1] | http://www.linux-ha.org/HeartbeatProgram |
| [2] | http://en.wikipedia.org/wiki/User_Datagram_Protocol |
| [3] | http://en.wikipedia.org/wiki/Unicast |
| [4] | http://www.linux-ha.org/ha.cf/UdpportDirective |
| [5] | http://en.wikipedia.org/wiki/Multicast |
| [6] | http://www.linux-ha.org/ha.cf |
This information provided courtesy of the Linux-HA project at http://linux-ha.org/