Cabletron Systems Cabletron CyberSWITCH CSX5500 User Manual

Also see for CyberSWITCH 5500: Quick start Manual

Contents

Central Site Remote Access Switch 309CONFIGURING A DVANCED IP ROUTINGDHCP Relay AgentDHCP C ONFIGURATION ELEMENTSDHCP/BOOTP R ELAY A GENT E NABLE /DISABLE F LAGA global flag that indicates whether the system is relaying the DHCP/BOOTP BOOTREQUESTmessages or not. The relay agent is disabled by default.R ELAY DESTINATION IP A DDRESSESThese are the IP addresses to which the system will relay BOOTREQUEST messages. For relaydestinations which are broadcast/multicast IP addresses, the network interface to which themessages should be relayed also needs to be configured.H OP C OUNT T HRESHOLDThis 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 valuegreater than this value will be discarded. The valid range is between 0 and 16, and the default is 4.DHCP B ACKGROUND INFORMATIONThe DHCP/BOOTP Relay Agent feature provides a solution to the dynamic IP address assignmentproblems in the ISDN WAN environment. Those IP host devices with the DHCP client softwarethat are connected to a central LAN through ISDN remote bridges are now able to obtain their IPaddresses from a DHCP server located on a central LAN.The Dynamic Host Configuration Protocol (DHCP) provides configuration parameters to IP hostdevices. DHCP consists of two components: a protocol for delivering host-specific configurationparameters (name servers, time servers and many more) from a DHCP server to a host; and amechanism for allocation of network addresses to hosts. Since remote devices are not always on amain network (a corporate LAN, Internet), and there are only limited IP addresses available, it isdesirable to assign the IP addresses to those devices only when they are connected to the mainnetwork. DHCP can be used to accomplish this task; and the DHCP/BOOTP Relay Agent helpsDHCP 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 ExtensionsDHCP/BOOTP Relay Agent processing is extensively discussed in RFC 1542.DHCP/BOOTP R ELAY A GENT E NVIRONMENTSThe following sections describe the different environments in which the DHCP/BOOTP RelayAgent may be used.