MAC addresses can be changed manually with the ifconfig command for tasks such as 'MAC Cloning' that may be required by DSL modems or interface bonding or similar. Furthermore ff:fe is inserted and fe80:: prepended. The name will change if the Ethernet card is replaced or the machine is cloned to new hardware. Convert MAC address to Link-local address or Link-local address to MAC address. Obviously this only works for machines on the same subnet. MAC addresses are unique identifiers assigned to network interface controllers (NICs) by the manufacturer. In fact, this conversion is a fundamental aspect of how data is transmitted over networks, whether it be on the internet or a local area network (LAN). Grep -v 'mac.local #DYN' /etc/hosts > /etc/hosts.new Spread the loveYes, MAC addresses can be converted to IP addresses. Of course it'll allocate it too as a side effect. The following command creates a link-local IPv6 address ( fe80:: prefix) from a MAC address: ipv6calc -action prefixmac2ipv6 -in prefix+mac -out ipv6addr fe80:: 00:21:5b:f7:25:1b. With outside help you can do the lookup on the DHCP server this DHCP client for example lets you query any MAC want. If you want to create a whole IPv6 address from a MAC (and a given prefix), you could use the excellent ipv6calc tool by Peter Bieringer. NOTE: this works even if they ignore PING packets because they can't ignore the ARP requests that are sent out first. There is even a special command for this arp-scan -localnet which forgets to do the PING. If you try to ping every (local) IP address your arp table arp -a will include all the MAC addresses and their assigned IPs. OTOH, if you really do want the IP address assigned to a particular MAC address the best you're going to do without outside help is to scan the subnet. ![]() everything is assigned an IP with dhcp but that IP never changes. That way you have the best of both worlds. The only way I've found to get around this is to make your DHCP server always assign a specific IP address to every device you have. This Mac Address to Binary allows you to easily convert an Mac address to its corresponding binary notation. Instead it makes the assumption that are aren't enough IP addresses available and preferentially reuses addresses. But it never uses this information to keep the same devices on stable IP addresses. This program records the Ethernet address of every device it has ever seen and the IP address that it assigned to it. I think you're running into what I believe is a serious mis-feature of the isc-dhcp server.
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