Section 3.5. Address binding

3.5. Address binding

One of the main functions of Radiator is to listen for UDP packets and TCP connections from other systems according to the Radiator configuration. The various Radiator clauses that can accept packets or connections from other systems all support the BindAddress parameter, which controls which IP addresses Radiator will listen on. IP packets sent to an IP address which is on the Radiator host, but which Radiator has not bound with BindAddress will not be received by Radiator.

The driver for this is that a single host may have multiple IP addresses, and those addresses may be IPv4, IPv6 and/or IPv6-over-IPv4. You may require Radiator to only honour requests directed to one of or a subset of the IP addresses for the host.

With BindAddress you can control which destination IP addresses Radiator will accept. You can specify one or more IPv4 or IPv6 addresses, including wildcard addresses, with the BindAddress parameter. The following forms may be used:

0.0.0.0 (the default) Any IPv4 address on the host
1.2.3.4 A specific IPv4 address on the host
:: Any IPv6 address on the host (and this may include any IPv4 address too, depending on how the host is configured)
2001:db8:148:100::31 A specific IPv6 address on the host

They may be combined in one BindAddress parameter like so:

BindAddress 0.0.0.0
BindAddress 192.87.30.31,2001:db8:148:100::31
BindAddress ::, 0.0.0.0

For more information about IPv6 support and IPv6 wildcard addresses, see Section 3.6. IPv6 support.

CAUTION

Wildcard addresses may require special attention. When a host is multihomed or uses alias IP addresses, the Radius replies from that host typically use the main address of the outgoing interface. In other words, requests sent to a certain address may be replied from a different address. You can work around this by configuring the addresses individually with BindAddress instead of using the wildcard address.