Use DHCP or a manual IP address on Mac An Internet Protocol (IP) address is a number that identifies each computer across the internet or a network. When you connect to the internet or an IP network, your computer needs an IP address. At first glance, the most obvious missing component in that page you linked to is any discussion about your Mac's own IP address. The article seems to be valid to setup a DHCP server to hand out addresses in the range 192.168.222.2-254 via en0. If I recall correctly, the fixed IP should not be inside the range your DHCP-Server hands out to clients. When the host has an old address from the same DHCP-Server, the server may hand out the old lease as long as it is valid, i.e. Lease time not expired. It would help, if you could provide more of your config. To find out the IP and hardware address of MAC. To get the IP address of the DHCP server from a MAC. To find out where the MacIntosh is getting its IP address. Environment: OSX; OS X; MacIntosh; DHCP; Procedure: To determine the hardware address and the ip of the wired interface, use ifconfig en0. Use DHCP or a manual IP address on Mac. An Internet Protocol (IP) address is a number that identifies each computer across the internet or a network. (DNS) server address. Enter the subnet mask and router in the labeled fields. To enter the DNS server address, click Advanced, click DNS, then click the Add button and enter the address.
After installing the DHCP role in Windows Server 2016 and setting up the first IPv4 Scopes to serve IP addresses to clients, it’s time to see how DHCP Filters work.
DHCP Filters are primarily used to further shield an infrastructure by allowing or denying specific clients based on their MAC addresses. Setting up DHCP Filters is quite simple and works at the server level, not at Scope level.
In a nutshell, with DHCP Filtering, you can filter clients, based on their MAC addresses, in order to either allow them to receive addresses from a DHCP Server or prevent (Deny) that from happening.
Before proceeding with the implementation of DHCP Filters, you will need to know how these filters are applied.
- When the Allow list is enabled, DHCP Server only serves IP addresses to the clients in this list automatically while rejecting all the others. If clients already had an IP address before filtering, then their IP will not automatically renew when Lease expires.
- When the Deny list is enabled, DHCP Server discards all the clients in this list. If clients already had an IP address and are now in the Deny list, then their Lease will not be renewed once they expire.
- By combining the two, Allow and Deny, the Deny list has precedence. This means that if a client is on the Deny list, it will be prevented in any case even if it is in the Allow list.
Now, let’s see how to configure DHCP filters.
Configure Filters in DHCP Server 2016
In the DHCP console, expand the server and IPv4 objects and go to the Filters object. Here, you’ll see two sub-folders (lists), Allow and Deny. By default, the two lists are deactivated and you can see this from the red down arrow, as shown in the figure below.
To add a DHCP Client to the Allow list, right-click and then click New Filter. Next, type the client’s MAC address and a description (optional) and click the Add button to complete the process.
The MAC address you type can be dashed (eg AA-BB-CC-DD-EE-FF) or without (eg AABBCCDDEEFF). You can also use the asterisk (*) as a wildcard to declare a range of MAC addresses. For example, AA-BB-*-DD-EE-FF, AA-BB-CC-*-*-*, AA-BB-*.
Respectively, follow the same procedure to add clients to the Deny list.
What is important to know is that the Deny list is superior to any other setting. So, if a client does not receive an IP address from a DHCP Server and the Filters are enabled, then your first action will be to check if it is in the Deny and then in Allow lists.
Additionally, you can move one or more clients from one list to another by right-clicking and then choose the corresponding option.
You can do the same for clients already in Address Leases, of course not having to type the MAC address.
Finally, do not forget to enable or disable the Allow and Deny lists by right-clicking and then choosing the corresponding option.
If the DHCP clients are VMs of a Hyper-V Server, you may prefer to set static MAC address instead of dynamic MAC addresses that are assigned by default.
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To alter the behavior of the IPv4 DHCP server, navigate to Services > DHCPServer in the web interface. The behavior of the IPv4 DHCP server iscontrolled there, along with static IP address mappings and related options suchas static ARP.
Choosing an Interface¶
The DHCP configuration page contains a tab for each interface with a static IPaddress. Each interface has its own separate DHCP server configuration, and theymay be enabled or disabled independently of one another. Before making anychanges, visit the tab for the correct interface.
General Options¶
The first setting on the tab enables or disables DHCP service for theinterface. To turn on DHCP for the interface, check Enable DHCP server on[name] interface. To disable the service, uncheck the box instead.
Under normal circumstances, the DHCP server will answerrequests from any client requesting a lease. In most environments this isnormal and acceptable behavior, but in restricted or secure environments thisbehavior is undesirable. With this option set, only clients with staticmappings defined will receive leases. This is a more secure practice but ismuch less convenient. This option is per-pool, meaning that if unknownclients are denied in the default range, another pool of IP addresses may bedefined that does not have the setting checked. The DHCP server will assignclients IP addresses out of that alternate pool instead.
Note
This will protect against low-knowledge users and people whocasually plug in devices. Be aware, however, that a user with knowledge ofthe network could hardcode an IP address, subnet mask, gateway, andDNS which will still give them access. They could also alter/spooftheir MAC address to match a valid client and still obtain a lease. Wherepossible, couple this setting with static ARP entries, access control in aswitch that will limit MAC addresses to certain switch ports for increasedsecurity, and turn off or disable unused switch ports.
The network address of the interface subnet, for reference purposes.
The subnet mask for the interface subnet, for reference purposes.
The range of available addresses inside the interface subnet,for reference and to help determine the desired range for DHCP clients. Thenetwork address and broadcast address are excluded, but interface addressesand Virtual IP addresses are not excluded.
This defines the DHCP address range, also referred to as the Scope orPool. The two boxes for Range tell the firewall the first and lastaddress for use as a DHCP pool. Addresses between the entered values,inclusive, will be used for clients which request addresses via DHCP. Therange must be entered with the lower number first, followed by the highernumber. For example, the default LAN DHCP range is based off of the subnetfor the default LAN IP address. It is 192.168.1.100 to 192.168.1.199.This range can be as large or as small as the network needs, but it must bewholly contained within the subnet for the interface being configured.
Additional Pools¶
The Additional Pools section defines extra pools of addresses inside of thesame subnet. These pools can be used to craft sets of IP addresses specificallyfor certain clients, or for overflow from a smaller original pool, or to splitup the main pool into smaller chunks with a GAP of non-DHCP IP addresses in themiddle of what used to be the pool. A combination of the MAC Address Controloptions may be used to guide clients from the same manufacturer into a specificpool, such as VoIP phones.
To add a new pool, click Add Pool and the screen will switch tothe pool editing view, which is nearly the same as the normal DHCP options,except a few options that are not currently possible in pools are omitted. Theoptions behave the same as the others discussed in this section. Items leftblank will, by default, fall through and use the options from the main DHCPrange.
Note
See the MAC Address Control section below for specifics on directingclients into or away from pools.
Servers¶
Two WINS Servers (Windows Internet Name Service) may be definedthat will be passed on to clients. If one or more WINS servers is required,enter their IP addresses here. The actual servers do not have to be on thissubnet, but be sure that the proper routing and firewall rules are in placeto let them be reached by client PCs. If this is left blank, no WINS serverswill be sent to the client.
The DNS Servers may or may not need filled in, depending on thefirewall configuration. If the built-in DNS Resolver or DNS Forwarder is usedto handle DNS, leave these fields blank and pfSense® will automaticallyassign itself as the DNS server for client PCs. If the DNS forwarder isdisabled and these fields are left blank, pfSense will pass on whichever DNSservers are defined under System > General Setup. To use custom DNSServers instead of the automatic choices, fill in the IP addresses for up tofour DNS servers here. In networks with Windows servers, especially thoseemploying Active Directory, it is recommended to use those servers for clientDNS. When using the DNS Resolver or DNS forwarder in combination with CARP,specify the CARP Virtual IP address on this interface here.
Other Options¶
This may also be left blank if this firewall is acting as the gatewayfor the network on this interface. If that is not the case, fill in the IPaddress for the gateway to be used by clients on this interface. When usingCARP, fill in the CARP Virtual IP address on this interface here.
Specifies the domain name passed to the client to form its fullyqualified hostname. If the Domain Name is left blank, then the domainname of the firewall it sent to the client. Otherwise, the client is sentthis value.
Controls the DNS search domains that are provided to theclient via DHCP. If multiple domains are present and short hostnames aredesired, provide a list of domain names here, separated by a semicolon.Clients will attempt to resolve hostnames by adding the domains, in turn,from this list before trying to find them externally. If left blank, theDomain Name option is used.
Note
The Domain Search List is provided via DHCP option 119. As ofthis writing, no Windows DHCP client of any version supports DHCP option119. Other operating systems such as BSD, Linux, and OS X do supportobtaining the Domain Search List via DHCP option 119.
Controls how long a lease will last when a client does notrequest a specific lease length. Specified in seconds, default value is7200 seconds (2 hours)
Limits a requested lease length to a stated maximum amountof time. Specified in seconds, default value is 86400 seconds (1 day).
If this system is part of a High Availability failovercluster, enter the real IP address of the other system in this subnet here.Do not enter a CARP Virtual IP address.
This checkbox works similar to denying unknown MAC addresses fromobtaining leases, but takes it a step further in that it also restricts anyunknown MAC address from communicating with this firewall. This stops would-be abusers from hardcoding an unused address on this subnet, circumventingDHCP restrictions.
Note
When using static ARP, all systems that need to communicate withthe firewall must be listed in static mappings before activating thisoption, especially the system being used to connect to the pfSense GUI.Also be aware that this option may prevent people from hardcoding an IPaddress and talking to the firewall, but it does not prevent them fromreaching each other on the local network segment.
By default, the ISC DHCP daemon maintains lease times inUTC. When this option is checked, the times on the DHCP Leases status pageare converted to the local time zone defined on the firewall.
This option, disabled by default, activates RRD graphing formonitoring the DHCP pool utilization.
Dynamic DNS¶
For Dynamic DNS settings, click Display Advanced to the right of that field,which displays the following options:
Check the box to enable registration of DHCP client names in DNSusing an external (non-pfSense) DNS server.
The domain name used for registering clients in DNS
The DNS server used for registering clients in DNS
The encryption key used for DNS registration
The secret for the key used for DNS registration
MAC Address Control¶
For MAC Address Control, click Display Advanced to show the lists of allowedand denied client MAC addresses. Each list is comma-separated and containsportions of MAC addresses. For example, a group of VoIP phones from the samemanufacturer may all start with the MAC address aa:bb:cc. This can beleveraged to give groups of devices or users separate DHCP options.
A list of MAC Addresses to allow in this pool. If a MAC address is inthe allow box, then all others will be denied except the MAC addressspecified in the allow box.
A list of MAC Addresses to deny from this pool. If a MAC address is inthe deny list, then all others are allowed.
It is best to use a combination of allow and deny to get the desired result,such as: In the main pool, leave allow blank and deny aa:bb:cc. Then in theVoIP pool, allow aa:bb:cc. If that extra step is not taken to allow the MACprefix in the additional pool, then other non-VoIP phone clients could receiveIP addresses from that pool, which may lead to undesired behavior.
This behavior may also be used to blacklist certain devices from receiving aDHCP response. For example to prevent Example brand printers from receiving aDHCP address, if MAC addresses all start with ee:ee:ee, then place that inthe deny list of each pool.
NTP Servers¶
To specify NTP Servers (Network Time Protocol Servers), click the DisplayAdvanced button to the right of that field, and enter IP addresses for up totwo NTP servers.
TFTP Server¶
click the Display Advanced button next to TFTP to display the TFTPserver option. The value in the TFTP Server box, if desired, must be an IPaddress or hostname of a TFTP server. This is most often used for VoIP phones,and may also be referred to as “option 66” in other documentation for VoIP andDHCP.
LDAP URI¶
click the Display Advanced button next to LDAP to display the LDAPServer URI option. LDAP Server URI will send an LDAP server URI to theclient if requested. This may also be referred to as DHCP option 95. It takesthe form of a fully qualified LDAP URI, such asldap://ldap.example.com/dc=example,dc=com. This option can help clientsusing certain kinds of systems, such as OpenDirectory, to find their server.
Additional BOOTP/DHCP Options¶
Other numeric DHCP options can be sent to clients using the AdditionalBOOTP/DHCP Options controls. To view these options, click Display Advancedin this section. To add a new option, click Add.
The DHCP option code number. IANA maintains alist of all valid DHCP options.
The choices and formats for each type may be a little counter-intuitive,but the labels are used directly from the DHCP daemon. The proper uses andformats are:
Free-form text to be sent in reply, such ashttp://www.example.com/wpad/wpad.dat or ExampleCompany.
A string of hexadecimal digits separated by a colon, such asc0:a8:05:0c.
Either true or false.
A positive Integer that will fitwithin the given data size, such as 86400.
A positive or negative Integer thatwill fit within the given data size, such as -512.
An IP address such as 192.168.1.1 or ahostname such as www.example.com.
The value associated with this numeric option and type.
For more information on which options take a specific type or format, see thelinked list above from the IANA.
Note
When using numbered custom options, be careful of the type. Some willbe OK on text/string but others are not.
For example, DHCP options for code 132 (and presumably 133) for VLAN IDmust be set for a type of unsigned integer 32.
Network Booting¶
To view the Network boot settings, click in the NetworkBooting section header bar.
Check to enable network booting options in DHCP
The IP address from which boot images are available
File name for the boot image (Non-UEFI)
File for 32-bit UEFI booting
File for 64-bit UEFI booting
String to target a specific device as the client’s root filesystemdevice, such as iscsi:(servername):(protocol):(port):(LUN):targetname.
Save Settings¶
After making changes, click Save before attempting to create staticmappings. Changes to settings will be lost if the browser leaves this pagewithout saving.
Static Mappings¶
Static DHCP mappings express a preference for which IP address will be assignedto a given client based on its MAC address. In a network where unknown clientsare denied, this also serves as a list of “known” clients which are allowed toreceive leases or have static ARP entries. Static mappings can be added in oneof two ways:
From this screen, click Add.
Add them from the DHCP leases view, which is covered later in this chapter.
On this screen, only the MAC address is necessary.
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The client MAC address which identifies the host to deliveroptions on this page, or by entering only the MAC address, it will be addedto the list of known clients for use when the Deny unknown clients optionis set.
Note
Client MAC address can be obtained from a command prompt on mostplatforms. On UNIX-based or UNIX-work-alike operating systems includingMac OS X, typing ifconfig-a will show the MAC address for eachinterface. On Windows-based platforms, ipconfig/all will show the MACaddress. The MAC address may also sometimes be found upon a sticker on thenetwork card, or near the network jack for integrated adapters. For hostson the same subnet, the MAC can be determined by pinging the IP address ofthe host and then running arp-a.
An ID sent by the client to identify itself.
The IP address field is needed if this will be a static IP addressmapping instead of only informing the DHCP server that the client is valid.This IP address is a preference, not a reservation. Assigning an IP addresshere will not prevent someone else from using the same IP address. If this IPaddress is in use when this client requests a lease, it will instead receivean address from the general pool. For this reason, the pfSense WebGUI doesnot allow assigning static IP mappings inside of the DHCP pool.
The hostname of the client. This does not have to match the actualhostname set on the client. The hostname set here will be used whenregistering DHCP addresses in the DNS forwarder.
Cosmetic only, and available for use to help track any additionalinformation about this entry. It could be the name of the person who uses thePC, its function, the reason it needed a static address, or theadministrator who added the entry. It may also be left blank.
Dhcp Server For Mac Installer
If checked, this entry will receive a static ARP entryin the OS tying this IP address to this MAC address.
Note
If this option is used rather than using the global static ARPoption, it does not prevent that MAC address from using other IPaddresses, it only prevents other MAC addresses from using this IPaddress. In other words, it prevents another machine from using that IP toreach the firewall, but it doesn’t stop the user from changing their ownIP address to something different.
Mac Os Dhcp Server
The remaining options available to set for this client are the same inbehavior to the ones found earlier in this section for the main DHCPsettings.
Dhcp Server App For Mac Os X
Click Save to finish editing the static mapping and return to the DHCPServer configuration page.