Chapter 1 Ip Routing Protocol Overview; Introduction To Ip Route And Routing Table; Ip Route And Route Segment - Huawei Quidway S3500 Series Operation Manual

Operation Manual - Routing Protocol
Quidway S3500 Series Ethernet Switches

Chapter 1 IP Routing Protocol Overview

Note:
When an Ethernet switch runs a routing protocol, it can perform the router functions.
Router that is referred to in the following and its icon represent a generalized router or
an Ethernet switch running routing protocols. To improve readability, this will not be
described in the other parts of the manual.

1.1 Introduction to IP Route and Routing Table

1.1.1 IP Route and Route Segment

Routers are implemented for route selection in the Internet. A router works in the
following way: It selects an appropriate path (through a network) according to the
destination address of its received packet and forwards the packet to the next router. It
works in this way hop by hop and the last router in the path is responsible for submitting
the packet to the destination host to complete the IP packet forwarding and the routing
across network segments.
In a network, the router regards a path for sending a packet as a logical route unit, and
calls it a Hop. For example, in the figure below, a packet sent from Host A to Host C, a
packet should go through 2 routers and the packet is transmitted through two hops and
router segments. Therefore, when a node is connected to another node through a
network, there is a hop between these two nodes and these two nodes are 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 counted as zero. In the following figure, the bold arrows
represent the hops. A router can be connected to any physical link that constitutes a
route segment for routing packets via the network.
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Chapter 1 IP Routing Protocol Overview