RADIUS Attribute Local-Loopback-Interface for L2TP

With this release, the RADIUS attribute Local-Loopback-Interface [26-3] is now supported for an L2TP LAC configured on an MX Series router. One can configure the Local-Loopback-Interface attribute on a RADIUS server to manage multiple LAC devices. This attribute is used as the LAC source address on an LNS tunnel for PPPoE subscribers tunneled over L2TP. When you use the Tunnel-Client-Endpoint attribute as the LAC source address, you must configure the Tunnel-Client-Endpoint attribute for each MX Series router that uses the same RADIUS server. Starting with this release, you can use the Local-Loopback-Interface attribute, which needs to be configured only once. When the LAC initiates an Access-Request message to RADIUS for authentication, RADIUS returns the Local-Loopback-Interface attribute in the Access-Accept message. This attribute contains the name of the loopback interface, either as a generic interface name such as "lo0" or as a specific name like "lo0.0." The MX Series router then uses the configured loopback interface IP address as the source address during tunnel negotiation with the LNS.