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366 C
HAPTER
16: IP R
OUTING
Figure 37 Routing Interfaces
To gain access to the module using TCP/IP or to manage the module
using the Simple Network Management Protocol (SNMP), set up an IP
interface to manage your system and at least one virtual LAN (VLAN). See
Chapter 14 for information about how to define a VLAN.
Routing Table With a routing table, a router or host determines how to send a packet
toward its ultimate destination. The routing table contains an entry for
every learned and locally defined network. The size of the routing table is
dynamic and can hold at least 25,600 entries; the actual number depends
upon what other protocols are being routed.
A router or host uses the routing table when the destination IP address of
the packet is not on a network or subnetwork to which it is directly
connected. The routing table provides the IP address of a router that can
forward the packet toward its destination.
The routing table consists of the following elements:
■
Destination IP address — The destination network, subnetwork, or
host.
■
Subnet mask — The subnet mask for the destination network.
■
Metric — A measure of the distance to the destination. In the Routing
Information Protocol (RIP), the metric is the number of hops through
routers.
L3
158.101.1.2
Network 1
158.101.1.1
158.101.2.2
Network 2
158.101.3.2
Network 3
158.101.2.1
158.101.3.1
Router
1
2
3
= Interface 1
= Interface 2
= Interface 3
1
2
3