Cabletron Systems CSX1200, CSX1000 manual Dhcp Configuration Elements, Dhcp Background Information

CONFIGURING ADVANCED IP ROUTING

DHCP Relay Agent

DHCP CONFIGURATION ELEMENTS

DHCP/BOOTP RELAY AGENT ENABLE/DISABLE FLAG

A global flag that indicates whether the system is relaying the DHCP/BOOTP BOOTREQUEST messages or not. The relay agent is disabled by default.

RELAY DESTINATION IP ADDRESSES

These are the IP addresses to which the system will relay BOOTREQUEST messages. For relay destinations which are broadcast/multicast IP addresses, the network interface to which the messages should be relayed also needs to be configured.

HOP COUNT THRESHOLD

This configuration element is used to limit the number of relay agents through which DHCP/ BOOTP BOOTREQUEST messages can travel. BOOTREQUEST messages with a hops field value greater than this value will be discarded. The valid range is between 0 and 16, and the default is 4.

DHCP BACKGROUND INFORMATION

The DHCP/BOOTP Relay Agent feature provides a solution to the dynamic IP address assignment problems in the ISDN WAN environment. Those IP host devices with the DHCP client software that are connected to a central LAN through ISDN remote bridges are now able to obtain their IP addresses from a DHCP server located on a central LAN.

The Dynamic Host Configuration Protocol (DHCP) provides configuration parameters to IP host devices. DHCP consists of two components: a protocol for delivering host-specific configuration parameters (name servers, time servers and many more) from a DHCP server to a host; and a mechanism for allocation of network addresses to hosts. Since remote devices are not always on a main network (a corporate LAN, Internet), and there are only limited IP addresses available, it is desirable to assign the IP addresses to those devices only when they are connected to the main network. DHCP can be used to accomplish this task; and the DHCP/BOOTP Relay Agent helps DHCP work over WAN environments.

For more detailed DHCP/BOOTP information, refer to the following specifications:

•RFC 1542: Clarifications and Extensions for the Bootstrap Protocol

•RFC 1541: Dynamic Host Configuration Protocol

•RFC 1534: Interoperation Between DHCP and BOOTP

•RFC 1533: DHCP Options and BOOTP Vendor Extensions DHCP/BOOTP Relay Agent processing is extensively discussed in RFC 1542.

DHCP/BOOTP RELAY AGENT ENVIRONMENTS

The following sections describe the different environments in which the DHCP/BOOTP Relay Agent may be used.

Workgroup Remote Access Switch 259