Shulou(Shulou.com)06/03 Report--

A brief introduction to the principle of forwarding data packets by level 3 routers

First, a brief description of the experimental environment

Both ​ routers are in the initial state, and Host A must communicate with Host B through gateways An and B.

Second, principle analysis

A hosa A broadcasts to A without knowing the MAC of the A gateway

Source ip:192.168.1.2

Source mac:00-11-12-21-11-11

Target ip:192.168.1.1

Target mac:ff-ff-ff-ff-ff-ff

The broadcast will be received by port e0 a will respond to the mac address and the hosta will send the ping packet to a

Two sources mac and IP modification

Source ip:10.1.1.1

Source mac:00-11-12-21-33-33

Target IP192.168.2.2

Target mac:ff-ff-ff-ff-ff-ff-ff

The broadcast packet will be received by the E1 port of B. Host has sent a ping packet.

Three-source ip mac change

Source ip 192.168.2.1

Source mac 00-11-12-21-55-55

Target IP192.168.2.2

Target mac:ff-ff-ff-ff-ff-ff-ff

HostB sees that the target is itself, give a response, give the mac address of its HostB to the HostBE0 port, and HostA will send the third ping packet to it.

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