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4-8 41-001343-02 REV04 – 05.2014
Option 43 Redirection and Configuration Server (RCS) Bypass
DHCP Option 43 includes the ability to bypass contacting Aastra's Redirection and Configuration Server (RCS), in addi-
tion to the previous support of setting the configuration server to contact.
A sub-option code 3 uses a boolean value (true or false) that controls whether or not the phone should contact the RCS
after a factory default. If this value is set to false, the RCS is not contacted. If it is set to true or is missing, then the RCS is
contacted as per previous releases. This can be used in conjunction with the existing code 2 sub-option to set the con-
figuration server.
Configuring RCS Bypass via Option 43 on a Linux DHCP Server
The following example illustrates how to configure RCS bypass via Option 43 on a Linux DHCP server.
option space AastraIPPhone;
option AastraIPPhone.cfg-server-name code 02 = text;
option AastraIPPhone.contact-rcs code 03 = boolean;
Subnet 192.168.1.0 netmask 255.255.255.0 {
#The 6757i phones do not contact the RCS but use the defined FTP server for configuration
#files.
class "vendor-class-57i" {
match if option vendor-class-identifier="AastraIPPhone57i";
vendor-option-space AastraIPPhone;
option AastraIPPhone.cfg-server-name "ftp://username:password@10.10.10.1";
option AastraIPPhone.contact-rcs false;
}
#The 6757iCT phones do not contact the RCS.
class "vendor-class-57iCT" {
match if option vendor-class-identifier="AastraIPPhone57iCT";
vendor-option-space AastraIPPhone;
option AastraIPPhone.contact-rcs false;
Using Option 120 on the IP Phone
DHCP Option 120 (as referenced in RFC 3361) allows SIP clients to locate a local SIP server (i.e. outbound proxy server)
that can be used for all outbound SIP requests. Using the “use dhcp option 120” configuration parameter, administra-
tors can enable support for DHCP Option 120 on the IP phones. This is particularly useful when service providers require
the IP phones to use certain outbound proxy servers or Session Border Controllers (SBCs) based on geographical loca-
tion and have provisioned the outbound proxy by using DHCP Option 120. The parameter is disabled by default.
Considerations
The following considerations must be taken into account when enabling support for DHCP Option 120 on the IP phones:
• If the parameter is enabled and DHCP Option 120 contains a valid value, the IP phones will use the server IP/name
obtained via DHCP Option 120 as the outbound proxy for both the Global SIP and Line 1 profiles.
• If Line 2 is configured and the outbound proxy is not defined, the phone will use the outbound proxy located in the
Global SIP profile.