DHCP, or Dynamic Host Control Protocol, is the service used to hand out IP addresses and other network settings by network appliances and servers. The DHCP Server built into macOS Server 5.4 on High Sierra is similar to the DHCP service that was included in Server 10.2 and 10.2 and from the good ‘ole Panther days. It’s pretty simple to use and transparent, just as DHCP services should be. To install the service, open the Server app and then click on the Show button beside Advanced in the server sidebar. Then click on DHCP. At the DHCP screen, you’ll see two tabs: Settings, used for managing the service and Clients, used…
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More Information About DHCP Leases in OS X
You can obtain a pretty decent amount of information about leases your OS X computer gets just by looking in the Network System Preference pane, for each interface. However, you can get a little lot more information, as with most things, from the command line. First, we’re going to take a look at en0 on our host and see what the MAC address is: ifconfig en0 ether Now, we can look in the /var/db/dhcpclient/leases directory to see a list of all of the leases we have running on our system. Based on the MAC address of our computer, we should see a file there that starts with the name of…
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Importing Computers Into DeployStudio
DeployStudio has the ability to import a csv file that is populated with the MAC address and a few specific settings. This allows you to prepopulate the database with the names that you want each machine to have. If you purchase a lot of machines from Apple then you can get a list of MAC addresses, or, you can use a bar code scanner to scan them as you’re unboxing. If you have a list of MAC addresses (en0), then you will need to format them in a very specific manner. Here, I have included a sample csv file with the data that goes into each field, which I have…
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DHCP Leases Expanded
DHCP provides IP addresses to clients. DHCP is critical to a number of Mac OS X Server technologies, most notably with NetBoot. In doing so, communications are comprised of 4 steps: Discovery, Offer, Acceptance, and Acknowledgment. In the Discovery step, a computer that needs an IP address sends a broadcast request to the environment. These typically remain local, although most routers will allow for configuring the gateway in such a way that UDP traffic is forwarded on to other subnets. The request also includes all of the options that the client will need, with options being anything beyond an IP address, each potential option with a numerical identifier per this…
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Mac OS X: Spoofing MAC Addresses in 5 Seconds
Every hardware network adapter has a unique MAC address. However, they’re not always what they seem. According to Wikipedia: MAC Spoofing is a hacking technique of changing an assigned Media Access Control (MAC) address of a networked device to a different one. The changing of the assigned MAC address may allow the bypassing of access control lists on servers or routers, either hiding a computer on a network or allowing it to impersonate another computer. I was talking to someone the other day about security and the topic of spoofing MAC addresses came up. They seemed to discount that this was usually a concern except for in super secure environments because they considered it an extremely complex process. Here’s my answer to…
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Open Directory and MAC Addresses
There are a number of items that get logged into Mac OS X Server with only the unique identifier of the MAC address. Sometimes it helps to find the name based on the MAC address. If you are in an environment using trusted binding you can use Open Directory to do so. To determine the name of a computer based on the MAC address from Open Directory, you can run the following from dscl: dscl /LDAPv3/127.0.0.1 -readall /Computers RecordName macAddress | grep -A 1 $MAC