Chapter 2 Ip Routing Protocol Overview; Introduction To Ip Route And Routing Table; Ip Route And Route Segment - H3C SecPath F1800-A Operation Manual

Operation Manual - Network and Routing Protocol
H3C SecPath F1800-A Firewall

Chapter 2 IP Routing Protocol Overview

2.1 Introduction to IP Route and Routing Table

2.1.1 IP Route and Route Segment

Routers are used for routing in the Internet. A router selects a proper route (through a
network) based on the destination address of its received packet and then forwards
the packet to the next router (the firewall). It works in this way hop by hop and the last
router in the route is responsible for sending the packet to the destination host.
For example, in
networks and 2 routers, that is, the hop count is 3 and 3 router segments have been
passed. It shows that, if a node is connected to another node through a network, there
will be a hop between these two nodes. They are thus deemed as adjacent in the
Internet. In the same principle, the adjacent routers refer to two routers connected to
the same network. The number of route segments between a router and hosts in the
same network is taken as zero. In
router does not care about which physical links constitute this route segment.
A
A A
C
Figure 2-1 About Hop
As the size of the network may differ greatly, the "length" of the router segments may
be different from each other. Therefore, for different networks, the number of route
segments multiplies a weighted coefficient to measure the actual length of the path.
If a router is regarded as a node and a route segment is regarded as a link in the
network, routing in the Internet is similar to routing in a simple network. Routing
Figure 2-1, from Host A to Host C, a packet should go through 3
Figure
R
Route Route
segment segment
R
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Chapter 2 IP Routing Protocol Overview
2-1, the bold arrows represent these hops. A
R
R
B
R