there is a switch in the home router.

來源: kzch 於 2015-01-07 09:09:18 [] [博客] [舊帖] [給我悄悄話] 閱讀數 : (978 bytes)
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I totally understand your textbook explanation. But the reality is much more complicated. All home routers have a built-in switch. The switch is for layer 2 interconnects between the LAN1-4 and WAN port. Even the WAN port is on this switch, but configured as a seperate VLAN.

The following page has the diagram of a typical home broadband router.
http://www.dd-wrt.com/wiki/index.php/Default_Configuration_Overview

As you can see, the home router actually consists of 3 components, a layer 2 switch with 6 ports (LAN1-4 on vlan0, WAN on vlan1, and the internal vlan trunk port 5=eth0), and a layer 2 bridge br0 (between eth1 for WLAN and vlan0), and a layer 3 router between br0(vlan0+eth1) and vlan1,

Regardless, my original point was that, with a router or switch, any host cannot see packets that are not send/received by itself. Only hosts on a hub can see all packets going through the hub using wireshark.

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