Enterasys Networks CSX6000 - Manual (Page 309)

Central Site Remote Access Switch 309
C ONFIGURING A DVANCED IP R OUTING
DHCP Relay Agent
DHCP C ONFIGURATION E LEMENTS
DHCP/BOOTP R ELAY A GENT E NABLE /D ISABLE F LAG
A global flag that indicates whether the system is relaying the DHCP/BOOTP BOOTREQUEST
messages or not. The relay agent is disabled by default.
R ELAY D ESTINATION IP A DDRESSES
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.
H OP C OUNT T HRESHOLD
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 B ACKGROUND I NFORMATION
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 R ELAY A GENT E NVIRONMENTS
The following sections describe the different environments in which the DHCP/BOOTP Relay
Agent may be used.