Juniper JUNOSE 11.1.X - BROADBAND ACCESS CONFIGURATION GUIDE 6-4-2010, Configuration Manual

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The services provided by integrating the E Series router’s DHCP external server
application with SRC software are similar to those provided when the DHCP local
server is integrated with SRC software. The router’s DHCP external application is
used together with other features of the router to provide subscriber management.
For additional information, see “Configuring Subscriber Management” on page 583.
NOTE: To ensure that DHCP external server with DHCP relay proxy processes
unicast reply packets (such as renewal ACK and NAK packets), you must configure
DHCP external server with the IP address of the DHCP relay proxy’s giaddr. This
configuration ensures that DHCP external server processes renewal ACK packets,
which in turn enables the updating of client leases.
Figure 14 on page 524 shows a network that includes an external DHCP server and
the E Series router.
Figure 14: DHCP External Server
In Figure 14 on page 524, the subscriber requests an address from the DHCP server
through the E Series router. All communication between the subscriber and the DHCP
server is monitored by the E Series router. After the subscriber receives an IP address,
the subscriber is able to access the Internet and use the value-added services provided
by the E Series router and by the SAE software. For this to occur, the edge network
must be using a DHCP relay function.
When the subscriber requests an IP address from the DHCP server, the E Series
router performs the following actions:
■
Identifies the subscriber’s IP address, MAC address, giaddr, and client identifier
■
Extracts the lease time, creates a shadow lease, and starts its own lease timer
that is associated with the subscriber
The E Series router views the subscriber as active once the subscriber sends a packet.
The router then performs the following actions:
■
Processes the subscriber’s IP address by using a route map
■
Extracts the dynamic subscriber interface profile (optional)
■
Creates the subscriber’s dynamic subscriber interface
524 ■
DHCP External Server Overview
JUNOSe 11.1.x Broadband Access Configuration Guide