3Com 4210 PWR - 6 Managing the Vlan; VLAN Overview

6
MANAGING THE VLAN
VLAN Overview To manage an Ethernet switch remotely through Telnet or the built-in Web server,
the switch need to be assigned an IP address, and make sure that a route exists
between the user and the switch. For the Switch 4210, only the management
VLAN interface can be assigned an IP address.
The management VLAN interface of a switch can obtain an IP address in one of
the following three ways:
■ Through the command used to configure IP address
■ Through BOOTP (In this case, the switch operates as a BOOTP client.)
■ Through dynamic host configuration protocol (DHCP) (In this case, the switch
operates as a DHCP client)
The three ways of obtaining an IP address cannot be configured at the same time.
That is, the latest IP address obtained causes the previously IP address to be
released. For example, if you assign an IP address to a VLAN interface by using the
corresponding commands and then apply for another IP address through BOOTP
(using the ip address bootp-alloc command), the former 0IP address will be
released, and the final IP address of the VLAN interface is the one obtained
through BOOTP.
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For details of DHCP, refer to the DHCP module.
Static Route A static route is configured manually by an administrator. You can make a network
with relatively simple topology to operate properly by simply configuring static
routes for it. Configuring and using static routes wisely helps to improve network
performance and can guarantee bandwidth for important applications.
The disadvantages of static route lie in that: When a fault occurs or the network
topology changes, static routes may become unreachable, which in turn results in
network failures. In this case, manual configurations are needed to recover the
network.
Default Route The switch uses the default route when it fails to find a matching entry in the
routing table:
■ If the destination address of a packet fails to match any entry in the routing
table, the switch uses the default route;
■ If no default route exists and the destination address of the packet is not in the
routing table, the packet is discarded, and an ICMP destination unreachable
message is returned to the source.
The default route can be configured through a static route and exists in the
routing table as a route destined to the network 0.0.0.0 (with the mask 0.0.0.0).