The following describes DHCPv4 service options that can be configured in Address Manager.
|DHCPv4 Service Option||Description|
|Default Lease Time||Specifies the default lease time that will be offered to DHCP clients.|
|Maximum Lease Time||Specifies the longest possible lease time that will be granted to a DHCP client.|
|Minimum Lease Time||Specifies the shortest possible lease time that will be granted to a DHCP client.|
|Client Updates||Indicates whether client updates should be used to maintain DDNS records for this client. When selected, the client updates its own DNS record on the server. When not selected, the DHCP server performs the update. This option is required for DHCP to perform DDNS updates.|
|DDNS Domain Name||Specifies the domain name appended to this client’s hostname to form the fully-qualified DNS name that will be dynamically updated by the DHCP server.|
|DDNS Host Name||Specifies the hostname that should be used for DDNS updates for
this client. If no value is specified, the hostname provided by the DHCP client will
be used. In the General section, define the following
|DDNS Reverse Domain Name||Specifies the domain name appended to the client's (reversed) IP address to form the fully-qualified reverse DNS name. By default, this value is in-addr.arpa.|
|DDNS TTL||Specifies the default TTL for DDNS records, specified as an integer value from 0 to 4,294,967,295 seconds. The values can be set in seconds, minutes, hours or days.|
|DDNS Updates||Indicates whether the server should attempt a DDNS update when the lease is confirmed.|
|Ping Check||Indicates whether the server should use an ICMP “ping” to ensure that only inactive IP addresses are offered to DHCP clients. By default, Ping Check is globally enabled.|
|Always Broadcast||Sets the server to always broadcast its responses to compensate for some clients that would not otherwise receive responses.|
|Always Reply (RFC 1048)||Indicates that the server should always reply with RFC 1048-style responses. This is true even if clients do not make RFC 1048-style requests.|
|Dynamic BOOTP Lease Length||Indicates the lease length after which a BOOTP client is assumed to be offline. Specified as an integer value between 0 to 4,294,967,295 seconds. The values can be set in seconds, minutes, hours or days.|
|File Name||The name of the initial boot file which is to be loaded by a client. Boot files are generally made available to clients by TFTP.|
|Get Lease Hostnames||When selected, the server looks up the domain name for each client and uses the information from the zone to set the hostname option for the client.|
|Minimum Seconds||Specifies the amount of time that the DHCP server waits before responding to client requests. A setting of 1 always results in the second request being answered rather than the first. This is useful for setting up a secondary DHCP server that allows the primary to respond to the first request. Specified as an integer from 0 to 255.|
|Next Server||Specifies the server where the boot file is located.|
|Server Identifier||Overrides the value that is sent to clients in the DHCP Server
Identifier option. This must be a valid IP address already assigned to the DHCP
server. This value is usually set automatically; using this option is not
|Site Option Space||Sets the site option space for a given DHCP scope. This option is only useful in combination with deployment of an option space definition in a DHCP Raw option.|
|Stash Agent Options||This check box causes the client to include the DHCP agent information from the initial DHCPREQUEST message in all subsequent messages.|
|Update Optimization||When selected, the DHCP server only attempts a DDNS update if it appears that client information has changed, rather than every time the client’s lease is renewed.|
|Update Static Leases||When enabled, the DHCP server will also perform DDNS updates for static (DHCP Reserved) leases.|
|Use Lease for Default Route||When selected, the client’s own IP address is sent as the router address rather than the actual address of the gateway. This can make some Windows clients ARP for all IP addresses if the router is set up for proxy ARP.|
|One Lease Per Client||When selected, the server clears all existing leases for a client upon the receipt of a new DHCPREQUEST message. This ensures that an interface obtains only one lease at a time for a segment.|
|Allow MAC Pools||Allows the selected MAC Pool access to DHCP services. After this option is set, MAC addresses not belonging to the selected MAC Pool are automatically denied. Multiple instances of this option may be added, to allow DHCP service to members of multiple MAC Pools.|
|Deny MAC Pools||Denies DHCP services to the specified MAC Pool wherever it is active. DHCP reservations take precedence over this option.|
|Deny Unknown MAC Addresses||Denies unknown MAC Addresses from using DHCP services wherever it is active.|
|Load Balance Override||Determines when the primary server or secondary server bypasses load balancing and responds to the client even if the client is supposed to be served by the peer server. Every message from a DHCP client has a secs field, which indicates for how long the client has been trying to contact a DHCP server. If the value in the secs field is greater than the load balance override parameter, the DHCP server always tries to respond to the client, regardless of the load balance split. The default setting is 3 seconds.|
|Load Balance Split||Informs the primary
server what portion of all clients it should serve. A value of 128
(active-active) indicates that both servers split the load evenly and that both
should respond to client requests using a load balancing algorithm to decide
which server should assign the address in each case. If the Load Balance Split
is set to 256 (active-passive), then only the primary server responds to client
requests. Despite the load balance split setting, the primary server generally
still only holds 50% of the available addresses for any failover pool and the
secondary server holds the other half, even though the secondary server does not
typically respond to requests. The default setting is 128.
Note: The value of 256 is not valid for earlier versions of the DNS/DHCP Server. For earlier versions of the DNS/DHCP Server, configure this option with the value of 255.
|Maximum Client Lead Time||Determines the maximum amount of time by which either server can extend a lease assigned by its peer without contacting the other server. The MCLT is also the recovery interval for the server that failed. As such, it increases the length of time to return to normal failover operations after a server failure. The default setting is 1800 seconds.|
|Max Response Delay||Defines how long a peer server waits without receiving any messages from its partner until it assumes that the partner has failed. It should be long enough for a server to notice that its peer is not responding, but prevents a temporary failure from breaking the failover pair. The default setting is 60 seconds.|
|Maximum Unacked Updates||This setting defines how many binding updates a DHCP server can send without receiving acknowledgments. The default setting is 10 updates.|
|Allow Class Members of||Allows DHCP clients who match a specific class value to receive an IP address at the level the option is set. This option also denies all non-matching hosts from receiving an IP address. One or more DHCP match classes must be created before setting this option. For more information about adding and editing DHCP Match classes, refer to DHCP match classes.|
|Deny Class Members of||Denies members of DHCP clients who match a specific class from receiving an IP address at the level the option is set. All clients who do not match this class value are able to receive an IP address. One or more DHCP match classes must be created before setting this option. For more information about adding and editing DHCP Match classes, refer to DHCP match classes. DHCP reservations take precedence over the specified by this option.|
|Conflict Detection||Address Manager for Windows DNS/DHCP (DDW) Only: Instructs a Windows DHCP server to ping the IP address it is about to assign to determine if the address is already in use. This helps to prevent duplicate IP addresses on the network. From the Retries list, select a value from 0 to 5.|
|Update Conflict Detection||When this option is
enabled and the DHCP server performs a DDNS update for the client, an additional
"guard" (either TXT or DHCID) record is added to DNS to record the DHCID of the
client that owns the DNS entry. Other clients are then not allowed to update or
remove the DNS entry by DHCP, even if they have the same hostname. This option is
enabled by default.
Attention: You must only configure the Update Conflict Detection Service option at the configuration and server levels.
|Do Reverse Updates||Controls whether or not DHCP
performs reverse DNS updates for clients. When this option is not present, servers
perform reverse updates by default. Use this option when you want to disable
|Deny Dynamic Bootp Clients||Allows or denies IP address assignment for BOOTP clients. If enabled, IP address assignment will be denied.|
|DDNS Update Style||Defines the DDNS update style
to ensure that the type of guard record remains the same for a given protocol. Use
this option when you are configuring a Dual-Stack Mixed Mode (DSMM) environment.
The DHCP server offering IPv4 leases must have a different update style than the
DHCP server offering IPv6 leases. The default setting is interim.
|DDNS Dual Stack Mixed Mode||Defines whether a
server operates in DSMM and whether DSMM rules are applied for DDNS conflict
resolution. The default value is disabled.
|DDNS Other Guard Is Dynamic||Defines whether the
presence of a DHCID "guard" record that was produced using a different DDNS update
style allows a DNS entry to be overwritten. Enabling this option can result in
static entries being overwritten. The default value is disabled.
|DDNS Guard ID Must Match||Defines whether a
client ID within a DHCID resource record must match the client ID of a DNS update
to permit DNS entries associated to that DHCID resource record to be overwritten.
The default value is enabled.