Answers:
A DHCP relay agent is a router or computer to be exact configured to listen for DHCP or BOOTP broadcast from DHCP clients and afterwards relay those messages to DHCP servers on different subnets.
DHCP clients use broadcasts from a DHCP server to immobilize a lease. Network routers do not elapse broadcasts, unless they are specifically configured to do so. his manner that a DHCP server can customarily provide IP address to clients which are located on alike subnet.
Many organization want to centralize their DHCP servers, as they find it easier to deal with. These organization must configure their lattice so that DHCP broadcasts will be passed from the client to the DHCP server. This can be done contained by any of the two ways: by configuring the routers which connect the subnets to forward DHCP broadcasts, or by configuring DHCP Relay Agents. The Routing and Remote Access Service underneath Microsoft Windows is competent to function as a DHCP relay agent.
DHCP Relay Agent vs. Dual DHCP Servers
To provide blemish tolerance, you should own at smallest two responders to DHCP client requests on every subnet.
If you own two or more subnets, you can use DHCP relay agents to provide eccentricity tolerance and to save regulation overhead at a minimum. For this, you should assign a DHCP server to respectively subnet, and next create non overlapping scopes for both subnets on both servers. Then you should deploy a DHCP relay agent on respectively subnet i.e. configured to forward packet, next to a slight bottleneck; to the DHCP sever contained by another subnet. This configuration will allow you to designate one DHCP server as the primary responder to DHCP requests, and to provide a backup route to another server if needed.
How a DHCP Relay Agent Works
The following steps describe how a DHCP relay agent works:
The DHCP client broadcasts a DHCPDISCOVER packet.
The DHCP relay agent on the client's subnet forwards the DHCPDISCOVER message to the DHCP server by using unicast.
The DHCP server uses unicast to convey a DHCPOFFER message to the DHCP relay agent.
The DHCP relay agent broadcasts the DHCPOFFER packet to the DHCP client's subnet.
The DHCP client broadcasts a DHCPREQUEST packet.
The DHCP relay agent on the client's subnet forwards the DHCPREQUEST message to the DHCP server by using unicast.
The DHCP server uses unicast to transport a DHCPACK message to the DHCP relay agent.
The DHCP relay agent broadcasts the DHCPACK to the DHCP client's subnet.
Using the Microsoft DHCP Server as a DHCP Relay Agent
Configuring a DHCP Relay Agent
Open Routing and Remote Access console.
Right click the server, and next click Configure and see Routing and Remote Access.
On the response page to Routing and Remote Access setup wizard page, click subsequent.
On the configuration page, select custom configuration, and afterwards click subsequent.
On the custom configuration page, select LAN routing, and next click subsequent.
On the completing Routing and Remote Access setup wizard page, click finish.
In Routing and Remote Access notice dialog box, click yes to start the service.
On the remote access/VPN server page, click finish.
In the option of console tree, expand the server, expand IP routing, and consequently select standard.
Right click common tab, and click the up to date routing protocol.
In the latest routing protocol page, click the DHCP Relay Agent and click Ok.
Configuring a DHCP Relay Agent near the IP address of the DHCP server
Open Routing and Remote Access console.
In the option of console tree, select DHCP relay agent.
Right click the DHCP relay agent, click properties.
On common tab, server address enclosed space, type IP address of the DHCP server that you craving to forward DHCP request to, click include, after click Ok.
Enabling the DHCP Relay Agent on a Interface of Router
Open Routing and Remote Access console.
In the option of console tree, select DHCP relay agent.
Right click the DHCP relay agent, click topical interface.
Select the interface on which you want to see the DHCP relay agent, and after click Ok.
In the properties dialog box of DHCP relay agent standard tab, product sure that relay DHCP packet is select.
Configure the boot threshold (seconds) and hop count threshold, if needed, and next click Ok
The Dynamic Host Configuration Protocol (DHCP) is a set of rules used by communications devices such as a computer, router or lattice adapter to allow the device to request and get an IP address from a server which have a chronicle of address available for assignment.
DHCP is a protocol used by network computers (clients) to acquire IP address and other parameter such as the non-attendance gateway, subnet curtain, and IP address of DNS servers from a DHCP server. The DHCP server ensure that adjectives IP address are creative, e.g., no IP address is assigned to a second client while the first client's assignment is valid (its lease have not expired). Thus IP address pool direction is done by the server and not by a human lattice administrator.
DHCP emerge as a standard protocol surrounded by October 1993. DHCP is a successor to the elder BOOTP protocol, whose lease be given for infinite time and did not support option. Due to the backward-compatibility of DHCP, drastically few networks verbs to use pure BOOTP. As of 2006, RFC 2131 (dated March 1997) provides the hottest DHCP definition. As of 2004, the up-to-the-minute non-standard of the protocol is RFC 3315 (dated July 2003), which describes DHCPv6 (DHCP contained by an IPv6 environment
DHCP is Dynamic Host Configuration Protocol.Its is utilized by some introduce yourself nodes to automatically retrieve their lattice configurations from a centralized server. ( One to One )
But a DHCP relay agent is a router or computer to be exact configured to listen for DHCP or BOOTP broadcast from DHCP clients and later relay those messages to DHCP servers on different subnets. ( One to Many)
Check these links for more detailed data
http://www.tech-faq.com/dhcp-relay-agent...
http://www.tech-faq.com/dhcp.shtml...
http://www.tcpipguide.com/free/t_dhcpmes...
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