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    Equal-Access Mode Overview

    In equal-access mode, the router enables access to non-PPP users. Non-PPP equal access requires the use of the router’s DHCP local server and SRC software, which communicates with a RADIUS server.

    The DHCP local server performs the following functions in equal-access mode:

    • Communicates with SRC software.
    • Assigns an IP address that enables the subscriber to access services.

    Local Pool Selection and Address Allocation

    The DHCP local server selects a DHCP pool from which to allocate an address using a number of parameters in a certain predefined sequence. The router compares the parameters with the local DHCP pools in the order presented in Table 1. When the router finds a match, it selects a pool based on the match and does not examine other parameters.

    Table 1: Local Pool Selection in Equal-Access Mode


    How the DHCP Local Server Uses the Field

    Framed IP address

    The client’s entry can be configured with a framed IP address, which the DHCP local server can get from the SRC software (formerly the SDX software).

    If the router selects a pool using a framed IP address, the DHCP local server attempts to allocate the framed IP address from the pool. If the framed IP address is not available, then the server allocates the next available address in the pool to the client.

    Pool name

    Each DHCP local pool has a pool name. The client’s entry can also be configured with a pool name, which the DHCP local server can get from the SRC software. The SRC software must be configured to send RADIUS attributes to DHCP.

    Domain name

    You can use a domain name as the name of a DHCP local pool. If the client logs onto the SRC software and RADIUS authenticates the client using a domain name, the DHCP local server receives the domain name from the SRC software.

    If the client’s domain name does not match the name of the DHCP local pool, the router attempts to match the client’s domain name to the domain name field within the pool.


    A DHCP local pool is configured with a network address. A gateway IP address (giaddr), which indicates a client’s subnetwork, can be presented to the DHCP local server in the client’s DHCP request message. The giaddr field in the DHCP request message contains the IP address of a DHCP relay agent. The router attempts to match the giaddr address in the DHCP request message with the network address of a DHCP local pool.

    Received interface IP address

    The router uses the IP address of the interface on which the DHCP packet is being processed and attempts to match it with the network address of a DHCP local pool. If the interface address matches with the IP address configured in the DHCP local address pool on the router, that pool is used to delegate the address to the client.

    The Connection Process

    The following sequence describes how the subscriber connects to the network for the first time using equal-access mode. Figure 1 illustrates the process.

    1. The subscriber’s computer boots and issues a DHCP request.
    2. The DHCP local server uses the SRC client to issue a COPS request to retrieve address pool information.
    3. After standard DHCP negotiations, the DHCP local server supplies an IP address to the subscriber’s computer from a local address pool, as described in the previous section.

      The router maintains a host route that maps the IP address to the router’s interface associated with the subscriber’s computer.

    4. The subscriber’s computer retains the IP address until the subscriber turns off the computer.

      Note: If a DHCP client attempts to renew its address and the DHCP server receives the request on a different interface than the interface that the client originally used, the DHCP server sends a NAK message to the client, forcing the client to begin the DHCP connection process again.

      Figure 1: Non-PPP Equal Access via the Router

      Non-PPP Equal Access via the Router

    Published: 2014-08-20