Table of Contents
This appendix contains some extra information of items concerning wireless LAN that are not directly related to KWiFiManager.
At first glance, the MAC address in the field Access Point seems to
be wrong in Ad-hoc mode because it changes the first two digits of the MAC address
to02
. But actually, this is a hardcoded feature in
wireless LAN cards.
Usually a card is connected to a “real” access point. Then the correct MAC address is shown. If you change to Ad-hoc (or “Peer-to-peer”) mode, one of the computers must act as a server for the other computers. The first computer that enters a network will set itself as server. So, all other computers connecting to the same Ad-hoc network will see that first computer as network server. But since this computer is not a “real” server (that is, it is not a permanently available access point), clients should be aware that the network they are connecting to is not a permanent one. IEEE standards for MAC addresses have a place reserved for such (rare) occasions: MAC addresses that are not globally valid have a bit set to one that shows that these addresses are “locally administered”. This bit is the second bit in transmit order, and the seventh bit in logical order and will hence raise the number of the MAC's first digit block from 00 to 02.
You can compare this sort of address to the non-global IP addresses like“192.168.*.*.”
So, the implementors of wireless networking agreed to give these“virtual” network servers a MAC address that is within the “locally administered” scope. To keep this virtual MAC address unique, they used a little trick: they only changed the first segment of the MAC address of the wireless LAN card, and since the remaining segments are still unique in the world, they have a unique address to use as network server.
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