DHCP 配置说明

DHCPv4 Service Option DescriptionDefault Lease Time Specifies the default lease time that will be offered to DHCP clients.Maximum Lease Time Specifies the longestpossible lease time thatwill be granted to a DHCPclient.Minimum Lease Time Specifies the shortestpossible lease time thatwill be granted to a DHCPclient.Client Updates Indicates whether clientupdates should be used tomaintain DDNS records forthis client. When selected,the client updates its ownDNS record on the server.When not selected, the DHCPserver performs the update.This option is required forDHCP to perform DDNSupdates.DDNS Domain Name Specifies the domain nameappended to this client’shostname to form the fully-qualified DNS name that willbe dynamically updated bythe DHCP server.Specifies the hostname thatshould be used for DDNSupdates for this client. Ifno value is specified, thehostname provided by theDHCP client will be used. Inthe General section, definethe following parameters:Type—select the type to beused as part of a DDNShostname value: IP Addressor MAC Address.Position—specify where youwish to add the data valueto the IP address or MACaddress to create the DDNShostname. Select Prepend toadd the data value specifiedin the Data field in frontof the IP address or MACaddress. Select Append toadd the data value specifiedin the Data field at the endof the IP address or MACaddress.DDNS Host NameData—specify data valuethat will be used to beprepended or appended to theIP address or MAC address toform the DDNS hostname. DDNS Reverse Domain Name Specifies the domain nameappended to the client's(reversed) IP address toform the fully-qualifiedreverse DNS name. Bydefault, this value is in-addr.arpa.DDNS TTL Specifies the default TTLfor DDNS records, specifiedas an integer value from 0to 4,294,967,295 seconds.The values can be set inseconds, minutes, hours ordays.DDNS UpdatesIndicates whether the servershould attempt a DDNS updatewhen the lease isacknowledged by the DHCPclient. When the Enabledcheck box is selected, theDHCP server updates DNSrecords on the DNS server.NOTE: DDNS Updates areenabled by default inProteus and this can cause aslow or unresponsive DHCPservice because the DHCPservice runs in a singlethread leading all DHCPlease updates are processedserially. In order to avoidthis issue, disable DDNSUpdates manually.Ping Check Indicates whether the servershould use an ICMP “ping”to ensure that only inactiveIP addresses are offered toDHCP clients. By default,Ping Check is globallyenabled.Always Broadcast Sets the server to alwaysbroadcast its responses tocompensate for some clientsthat would not otherwisereceive responses.Always Reply (RFC 1048)Indicates that the servershould always reply with RFC1048-style responses. Thisis true even if clients donot make RFC 1048-stylerequests.Dynamic BOOTP Lease Length Indicates the lease lengthafter which a BOOTP clientis assumed to be offline.Specified as an integervalue between 0 to4,294,967,295 seconds. Thevalues can be set inseconds, minutes, hours ordays.File Name The name of the initial bootfile which is to be loadedby a client. Boot files aregenerally made available toclients by TFTP.Get Lease Hostnames When selected, the serverlooks up the domain name foreach client and uses theinformation from the zone toset the hostname option forthe client.Minimum Seconds Specifies the amount of timethat the DHCP server waitsbefore responding to clientrequests. A setting of 1always results in the secondrequest being answeredrather than the first. Thisis useful for setting up asecondary DHCP server thatallows the primary torespond to the firstrequest. Specified as aninteger from 0 to 255.Next Server Specifies the server wherethe boot file is located. Server Identifier Overrides the value that issent to clients in the DHCPServer Identifier option.This must be a valid IPaddress already assigned tothe DHCP server. This valueis usually setautomatically; using thisoption is not recommended.Site Option Space Sets the site option spacefor a given DHCP scope. Thisoption is only useful incombination with deploymentof an option spacedefinition in a DHCP Rawoption.Stash Agent Options This checkbox causes theclient to include the DHCPagent information from theinitial DHCPREQUEST messagein all subsequent messages. Update Optimization When selected, the DHCPserver only attempts a DDNSupdate if it appears thatclient information haschanged, rather than everytime the client’s lease isrenewed.Update Static Leases When enabled, the DHCPserver will also performDDNS updates for static(DHCP Reserved) leases.Use Lease for Default Route When selected, the client’sown IP address is sent asthe router address ratherthan the actual address ofthe gateway. This can makesome Windows clients ARP forall IP addresses if therouter is set up for proxyARP.One Lease Per Client When selected, the serverclears all existing leasesfor a client upon thereceipt of a new DHCPREQUESTmessage. This ensures thatan interface obtains onlyone lease at a time for asegment.Allow MAC Pools Allows the selected MAC Poolaccess to DHCP services.After this option is set,MAC addresses not belongingto the selected MAC Pool areautomatically denied.Multiple instances of thisoption may be added, toallow DHCP service tomembers of multiple MACPools.Deny MAC Pools Denies DHCP services to thespecified MAC Pool whereverit is active. DHCPreservations take precedenceover this option.Deny Unknown MAC Addresses Denies unknown MAC Addressesfrom using DHCP serviceswherever it is active.Allow Class Members of Allows DHCP clients whomatch a specific class valueto receive an IP address atthe level the option is set.This option also denies allnon-matching hosts fromreceiving an IP address. Oneor more DHCP match classesmust be created beforesetting this option. Formore information aboutadding and editing DHCPMatch classes, refer to DHCPMatch Classes.Deny Class Members of Denies members of DHCPclients who match a specificclass from receiving an IPaddress at the level theoption is set. All clientswho do not match this classvalue are able to receive anIP address. One or more DHCPmatch classes must becreated before setting thisoption. For more informationabout adding and editingDHCP Match classes, refer toDHCP Match Classes. DHCPreservations take precedenceover the specified by thisoption.Conflict Detection Proteus DDW Only: Instructsa Windows DHCP server toping the IP address it isabout to assign to determineif the address is already inuse. This helps to preventduplicate IP addresses onthe network. From theRetries list, select a valuefrom 0 to 5.Update Conflict Detection When enabled, the serverused in combination withDDNS updates to enforceownership of a DNS name.When this option is enabledand the DHCP server performsa DDNS update for theclient, an additional TXTrecord will be added to DNSto record the DHCID of theclient that owns this DNSentry. Other clients willnot be allowed to update orremove this DNS entry byDHCP, even if they have thesame hostname. This optionis enabled by default.Do Reverse UpdatesControls whether or not DHCPperforms reverse DNS updatesfor clients. When thisoption is not present,servers perform reverseupdates by default. Use thisoption when you want todisable reverse updates.When this option is presentand the Enabled checkbox isselected, the selectedserver performs reverseupdates. This is theequivalent of this optionnot being present.When this option is presentand the Enabled checkbox isnot selected, the selectedserver does not performreverse updates.。