Document pseudo-interfaces.

diff --git a/client/dhclient.conf.5 b/client/dhclient.conf.5
index 13bd822897d9c9158309ded63056495f6997da0c..cde23f9b2370d616f9dc93ace1c502e385739945 100644 (file)
--- a/client/dhclient.conf.5
+++ b/client/dhclient.conf.5
@@ -449,6 +449,36 @@ parameters will then be used only for the interface that matches the
 specified name.   Interfaces for which there is no interface
 declaration will use the parameters declared outside of any interface
 declaration, or the default settings.
+.PP
+ \fBpseudo "\fIname\fR" "\fIreal-name\fB" { \fIdeclarations ... \fB }
+.PP
+Under some circumstances it can be useful to declare a pseudo-interface 
+and have the DHCP client acquire a configuration for that interface.
+Each interface that the DHCP client is supporting normally has a DHCP
+client state machine running on it to acquire and maintain its lease.
+A pseudo-interface is just another state machine running on the
+interface named \fIreal-name\fR, with its own lease and its own
+state.   If you use this feature, you must provide a client identifier
+for both the pseudo-interface and the actual interface, and the two
+identifiers must be different.   You must also provide a seperate
+client script for the pseudo-interface to do what you want with the IP
+address.   For example:
+.PP
+.nf
+       interface "ep0" {
+               send dhcp-client-identifier "my-client-ep0";
+       }
+       pseudo "secondary" "ep0" {
+               send dhcp-client-identifier "my-client-ep0-secondary";
+               script "/etc/dhclient-secondary";
+       }
+.fi
+.PP
+The client script for the pseudo-interface should not configure the
+interface up or down - essentially, all it needs to handle are the
+states where a lease has been acquired or renewed, and the states
+where a lease has expired.   See \fBdhclient-script(8)\fR for more
+information.
 .PP
  \fBmedia "\fImedia setup\fB"\fI [ \fB, "\fImedia setup\fB", \fI... ]\fB;\fR
 .PP