Heartbeat IPaddr resource agent

The IPaddr resource agent is used by Heartbeat to configure IPv4 ServiceAddresses. Most resource groups will contain at least one IPaddr or IPaddr2 resource.

The basic syntax of an IPaddr resource is

  IPaddr::ip-address[/netmask[/interface][/broadcast]]

This can be abbreviated simply to:

  ip-address[/netmask[/interface][/broadcast]]

So, the following forms of addressing are legal:

  address
  address/netmask
  address/netmask/broadcast
  address/netmask/interface
  address/netmask/interface/broadcast

By far the most common case is the simplest one:

  ip-address

In this form, appropriate defaults are taken as described below.

Default Interface

If the interface was omitted, we use the system routing tables to determine which interface would be used to route a packet to the given address. That is, IPaddr selects the preferred interface for sending packets to that subnet. If no such interface can be found, heartbeat will issue a message something like this:

ERROR: unable to find an interface for given-ip-address

Default netmask

If the CIDR netmask is omitted, we choose the netmask associated with the route to the subnet to which packets to the given IP address would be routed. That is, we simply look up the routing information for that address, and use it to compute the correct netmask (and other items as described below).

Default broadcast address

If the broadcast address was omitted, IPaddr defaults to the highest address in the subnet (the usual default).

Examples

  135.9.216.100
  135.9.216.100/24                  (implies a 255.255.255.0 netmask)
  135.9.216.100/24/135.9.216.255
  135.9.216.100/24/eth0
  135.9.216.100/24/eth0/135.9.216.255

Special Note

The interface mentioned above does not include an alias number. Heartbeat assigns them dynamically according to the available alias names.

IPaddr has a limit of around 100 aliases it can manage for any given interface.

See http://www.doom.net/docs/netmask.html for a table explaining CIDR address format and their relationship to life, the universe and everything.

See Also

ResourceAgent, HeartbeatResourceAgent, IPaddr2 resource agent, Linux Hacks article on our send_arp command

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