Cabletron Systems CSX1000, CSX1200 Bridge to Bridge Environment, Router to Bridge Environment

USER’S GUIDE

Bridge to Bridge Environment

CSX1200	Using bridging
	DHCP
	DHCP Server
Remote Bridge

DHCP Client DHCP Client

As shown in the picture above, when a remote LAN is connected with bridge devices, the DHCP server and clients communicate with each other as if they were on the same LAN. This is one example configuration of how DHCP can be used to accomplish the dynamic IP address assignment to the remote IP devices. (Note: This topology works without enabling any additional DHCP/BOOTP features.)

Router to Bridge Environment

Although the bridge to bridge environment is a simple way to deploy the dynamic IP address assignment using DHCP, it has some disadvantages. The major disadvantage is a broadcast storm. Since all remote LANs are connected through bridge devices, all broadcast traffic will be forwarded from one remote LAN to all the other LANs, and from a central LAN to all other remote LANs. This is especially undesirable in the environment where there are many remote LANs.

To solve this problem, IP routing should be turned on at the central site. Enabling routing at the central site will prevent the broadcast traffic from traveling all over the wide area network. Unfortunately, this also keeps DHCP messages from being exchanged, as they are transmitted in the broadcast packets. The DHCP Relay Agent resolves this situation, allowing only DHCP messages to be forwarded without letting all other broadcast traffic get through.

260 CyberSWITCH