Route Selection Through The Routing Table - Huawei Quidway S3500 Series Operation Manual

Operation Manual - Routing Protocol
Quidway S3500 Series Ethernet Switches
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Figure 1-1 About hops
As the networks may have different sizes, the segment lengths connected between two
different pairs of routers are also different. The number of route segments multiplies a
weighted coefficient can serve as a weighted measurement for the actual length of the
signal transmission path.
If a router in a network is regarded as a node and a route segment in the Internet is
regarded as a link, message routing in the Internet works in a similar way as the
message routing in a conventional network. Message routed through the shortest route
may not always be the optimal way route. For example, routing through 3 LAN route
segments may be much faster than that through 2 WAN route segments.

1.1.2 Route Selection through the Routing Table

The key for a router to forward packets is the routing table. Each router saves a routing
table in its memory, and each entry of this table specifies the physical port of the router
through which the packet is sent to a subnet or a host. Therefore, it can reach the next
router in via a particular path or reach a destination host via directly connected network.
A routing table has the following key entries:
Destination address: It is used to identify the destination IP address or the
destination network of IP packet, which is 32 bits in length.
Network mask: It is made up of several consecutive "1"s, which can be expressed
either in the dotted decimal format or by the number of the consecutive "1" s in the
mask. Combining with the destination address, it is used to identify the network
address of the destination host or router. If the destination address is ANDed with
the network mask, you will get the address of the network segment where the
destination host or router is located. For example, if the destination address is
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Route Route
segment segment
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Chapter 1 IP Routing Protocol Overview
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