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JUNOSe 11.1.x Broadband Access Configuration Guide
Configuring DHCP Proxy Clients
DHCP proxy client support enables the router to obtain an IP address from a DHCP
server for a remote PPP client. Each virtual router (acting as a DHCP proxy client)
can query up to five DHCP servers.
For PPP users, the router acts as a DHCP client to obtain an address for the user.
This is referred to as DHCP proxy.
The process for PPP users is as follows:
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Dynamic IP addresses are leased to the remote host for a specific period of time,
which can range from minutes to days. At the halfway point in the lease period, the
proxy client requests an extension from the DHCP server on behalf of the remote
host. The lease is extended for a period specified in the acknowledgment (ACK)
message returned by the DHCP server typically equal to the original lease. If the
DHCP server returns a negative acknowledgment (NAK) message to the proxy client,
the proxy client notifies the server on the router that the extension has been denied.
The AAA server logs out the remote host and frees the IP address for reuse.
When a remote host disconnects, the AAA server notifies the proxy client that the
IP address is available for reuse. The proxy client informs the DHCP server, which
can now reassign that IP address.
For additional information on managing client bindings, see "Viewing and Deleting
DHCP Client Bindings" on page 466.
To configure a proxy client from Global Configuration mode:
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Configuring DHCP Proxy Clients
The remote user dials in, and the client requests RADIUS authentication.
The AAA server on the router sends a request to the DHCP proxy client on the
router for an IP address to be assigned to the remote user's host.
The proxy client assumes the role of DHCP client and sends a discovery message
to each DHCP server.
One or more of the DHCP servers responds with an offer message containing
an IP address.
The proxy client determines which offer to accept and sends a message to that
DHCP server requesting that IP address.
The DHCP server responds to the proxy client with an acknowledgment message.
The proxy client passes the IP address to the authentication, authorization, and
accounting (AAA) server on the router, and the AAA server returns the address
to PPP. PPP then assigns the address to the remote host. The new IP address is
included when the router next updates its routing table.
Specify the address of the DHCP server that will provide IP addresses for remote
hosts. You can specify a maximum of five DHCP servers.
host1(config)#ip dhcp-server 10.6.128.10
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Troubleshooting
