3com 3031 Instruccion De Instalación

This chapter tells you the following:

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How Reliability is provided on 3Com Routers

Any software or hardware error in data communication may break a network 
connection and, thereby causing data transmission failure. To prevent network 
device or line fault from breaking data communication, v2.0 software on 3Com 
routers provides a backup center, Virtual Router Redundancy Protocol (VRRP) and 
hot backup technologies to ensure the availability of a backup scheme to 
guarantee smooth data communication, and to make the network more robust 
and reliable. 

The backup center provides perfect backup functions for the communication lines 
between routers. By specifying the main interface and its backup interfaces and 
adjusting such parameters as priority and switchover delay for various backup 
interfaces, the backup interfaces will replace the main interface when the latter 
fails so as to ensure the normal operation of the borne services and to improve the 
reliability of the communication lines to a great extent. In v2.0 software on 3Com 
routers, every physical interface, sub-interface or logical channel (such as a X.25 
virtual circuit) on an interface can serve as a main interface. Except Ethernet 
interfaces, every physical interface, virtual interface template or logical channel of 
an interface can serve as a backup interface for another interface or logical 
channel. 

VRRP improves the reliability of the external connections of a network and applies 
to the LANs (such as Ethernet) supporting multicast or broadcast. Several routers 
can form a backup group (also taken as a virtual router), acting as the centralized 
output gateway of local network, when the routers in the backup group are 
transparent to local network. A router in the backup group is engaged in packet 
forwarding, a standby router is ready for replacing the active router, and the other 
routers are in monitoring status. When the active router fails, it will be replaced by 
the standby router and a new router is selected from the monitoring routers as 
standby router. This makes it possible for a local host to continue its operation 
without any modification, thus improving communication reliability. 

VRP provides hot backup mechanism for high-end devices. A high-end device is 
usually configured with two MPUs, that is, a master MPU and a slave MPU. When 
the master board fails, the system automatically switches to the slave board for 
operation. In addition, hot backup can implement software upgrade without 
interrupting services to ensure the normal operation of the services.