Option created with expression not send
W.J.M. Nelis
Wim.Nelis at nlr.nl
Thu Dec 23 13:23:28 UTC 2010
Hello,
for (Avaya) IP telephones, dhcpd passes the voice-vlan. If the option is
build using the syntax
option <Option> <Value> ;
it works like advertised. However, we need to move to multiple
voice-vlans, thus an assignment using the syntax
option <Option> = <Expression> ;
is used. The Option created in this way is not passed in the DHCPOFFER
or DHCPACK.
In more detail, using the following configuration in dhcpd.conf
option AvayaIpPhoneOpt242 code 242 = text ;
class "vendor-classes" {
match option vendor-class-identifier ;
}
subclass "vendor-classes" "ccp.avaya.com" {
option AvayaIpPhoneOpt242= "L2Q=1,L2QVLAN=81,VLANTEST=0" ;
}
does send the parameters in the DHCPOFFER and DHCPACK. However, with the
following configuration
option AvayaIpPhoneOpt242 code 242 = text ;
class "vendor-classes" {
match option vendor-class-identifier ;
}
subclass "vendor-classes" "ccp.avaya.com" {
set voice-vlan = <Expression> ;
log( info, concat("DHCPDEBUGA voice-vlan=",voice-vlan) ) ;
option AvayaIpPhoneOpt242 = concat( "L2Q=1,VLANTEST=0,L2QVLAN=",
voice-vlan ) ;
set temp = concat( "L2Q=1,VLANTEST=0,L2QVLAN=", voice-vlan ) ;
log( info, concat("DHCPDEBUGB opt.242=",temp) ) ;
}
does not work. This happens both in dhcpd version 3.1.3 and in dhcpd
version 4.2.0-P2. Using log-statements, it can be shown that variable
voice-vlan is set to the appropriate value, as well as the variable
temp. Using Wireshark, it can be shown that option 242 is not send to
the client, thus the value of the option is probably NULL.
What do we need to do to send a computed voice-vlan to a DHCP client?
Wim Nelis.
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