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ͥåȥڥꥹȤλкȤǤͥåȥڥꥹȻι
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кʤ麸κǤܤ֥ͥڡץ꡼ʵɾҡˤǡ
ͥåȥڥꥹȻ˹ʤȡͥåȥ˴ؤμ䵻ѤǤʤɲϤʸϤȤˤĤޤ
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ƥꡧ10.ץꥱءL5L7 > 10.2 DHCP

DHCP(Dynamic Host Configuration Protocol)Ȥϡդ̤ꡢưŪ˥ۥȡHostˤPCΥͥåȥConfigrationˤ򤹤ץȥProtocol)Ǥ
ǤDHCP(Dynamic Host Configuration Protocol)˴ؤơDHCPϡIPɥ쥹ʤɤΥͥåȥ³ɬפʾIPɥ쥹֤ͭ򼨤꡼ֵڤӥ֥ͥåȥޥʤɤΥץDHCPФ鼫ưŪ˼PCꤹ뤿ΥץȥH21AP-5ˡפȽҤ٤Ƥ롣
DHCP


ѥϡͥåȥϡޤΤ褦ˡIPɥ쥹ưŪ˼פˤޤ
dhcp_ͥåȥڥꥹ

UDP67֤ФUDP68֤饤ȤǻȤݡ
DHCPȤˤʤΤBOOTPBooTstrap Protocol)DHCPBOOTP˳ĥƤꡢ륪ץʤɤʤƤ롣
ͥåȥڥꥹȤܻؤSE졩 

ʣDHCPФȤ饤ȤϤɤΥФ饢ɥ쥹ΤǤ
ŪˤϡǤ᤯DHCPФIPɥ쥹롣ͥåȥŪʵΥᤤΤ뤳Ȥˤʤ뤬ΤȤΥߥ󥰤ˤꡢ̤Ѥꤵ롣
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ȤȤϡDHCPФĹȤˡޥȤʤDHCPФʧΤХåå¦DHCPФʧФΤʬʤȤȤǤ͡
ǤϡʧФǧȤʤɡͤˤȤäƤݤǤ롣
ǡХåå¦DHCPФǤϡʧФΥߥ󥰤򤺤餹Ȥٱ뤳Ȥ롣

ĤDHCPѤå
ü򤹤ɬפʤäѹ1000ͤѤΤѤǤ롣ѥȤ⤽ѥեưƻȤʤɤ
ͲǤϡIPɥ쥹ʤɤȤꤹѻʤH21AP-5ˡפȽҤ٤Ƥ롣
IPɥ쥹ΰ층ԤDHCPФΥ
IPɥ쥹ͭѡʴȤǤϥץ饤١ȥɥ쥹ȤΤǡޤåȤǤϤʤ
ͲǤϡ֥꡼֤ꤹ뤳Ȥˤäơ֤ȤIPɥ쥹κѤԤΤǡDHCPФϿIPɥ쥹κ︺Ǥ롣H21AP-5ˡפȽҤ٤Ƥ롣

DHCPѤˡIPɥ쥹Ѥå
DHCPФ󤷤ƤͥåȥѤǤ롣
DHCPФΥȤϷ빽롣Ȥˣ椺֤ΤѤʤΤǡ졼Ȥ򤹤뤬ȥͥåȥ󤷤Ȥʤ
IPɥ쥹üʥ桼ˤ꤬䤹
DHCPΥǥåȤˤʤ뤬˻PCĤʤȤƤ⡢ưǥͥåȥ³ǤƤޤᡢƥ夯ʤ롣ȤϤǤ⼫ʬꤹƱʤ櫓Ǥ뤬ƥμ夵Ȥ̣ǤϡDHCPΤۤ夤ʵ꤫⤷ʤ

DHCP꤫
ФʤɡIPˤʤȡ̿ƶǤ䤹Τϸˤ롣
ƥηǰʤĶǤС̤ͤDHCPȤ롣

¦
֥ͥå/ͥåȥޥ
ʧIPɥ쥹ϰ
ɥᥤ󥵥եå
ǥեȥȥ
DNSWins

ʧФIP
ǤIPʧФMACɥ쥹б

H21AP-5ˤˤDHCPåΤ礬Ҥ٤Ƥ롣
DHCPtejun
1)DHCP DISCOVER 饤ȤФõDiscoverˡ֥ɥ㥹ȡ

2)DHCP OFFERDHCPФDHCP饤ȤФIPǤɤơOfferˤФ˥㥹ȡOfferˤIPɥ쥹Ǥʤ֥ͥåȥޥDNSʤɤΥץޤޤ롣

3)DHCP REQUEST饤Ȥλ롣֥ɥ㥹ȡ

4)DHCP ACK˥㥹
2)4)MircosoftҤDHCPФISCDHCPФˤäƥ˥㥹ȤǤ̵礬롣
DHCP2


Ĥ

嵭1)DHCP DISCOVERǤϡDHCPФʬʤΤǥ֥ɥ㥹Ȥɬפޤ
ʤ3)DHCP REQUEST֥ɥ㥹ȤɬפΤǤ
DHCPФʣ¸ߤ礬ޤξ硢IPɥ쥹ꤷȤ򥻥Ⱦ̣ޤʤȡ¾DHCPФϡ٤⥯饤ȤIPʧФȤƤޤ
ľΩ

äѤޤ
DHCPФʣ椢äƤʤΤǤ
ŪˤϾ嵭DHCP REQUESTǥ֥ɥ㥹ȤѤƤ뤳Ȥˤȯʤ饤ȤϤɤDHCPФ򤹤뤫Ȥȡե졼ब®夷ΤѤ롣
DHCPХեȤ󶡤ƤҤϿ侩Ƥʤ㳲ȯǽ뤫LinuxǤϤΤξĹʥե륪Сˤεǽ󶡤Ƥ롣

ޤ
DHCPIPɥ쥹Ǥʤä硢MircosoftҤʤǤAPIPAAutomatic Privete IP Addresˤˤ뼫ưץ饤١IPɥ쥹169.254.X.X)꿶롣IPɥ쥹Ǥ¾PC̿ϤǤʤ

ľΩDHCP 졼ȤȤ
DHCPѤΤȡ
Ǥϡ֥롼ϡDHCP饤Ȥͥåȥ³ɬפʾʤɤμ׵ȡDHCP졼ȵǽˤäơDHCPФˤ׵ž롣ޤDHCPФαDHCP饤Ȥž롣H21AP-5ˡפȽҤ٤Ƥ롣
CiscoǤϡʲԤȤǡDHCP졼ȤͭˤȤȤˡDHCPФꤷƤ롣
#ip helper-address 192.168.1.100

Ȥ
PC롼ѡˢWANDHCP
롼ޤǤϥ֥ɥ㥹ȡ
롼DHCPФޤǤIPѥå

ʤDHCP졼ȤɬפʤΤ
DHCPΥѥåȤϥ֥ɥ㥹Ȥ뤿ᡢWANĶʤDHCPФ֥ɥ㥹ϰ֤ǤФŪϤʤDHCPФ餱ˤʤäƤޤ
ޤDHCPФĹΤϥŪѤʤΤǡ졼ȤȤȤǡDHCPΥХ꤬Ǥ롣

DHCPФϡɤäʧIPΤ
DHCPФϡʣΥȤIP׵᤬롣
ʧIPɤäƤΤ

DHCP졼ȤˤϡѸΥ롼IPɥ쥹LAN¦ˤäƤꡢIPɥ쥹Ʊ쥻ȤIPɥ쥹ʧޤ

DHCPᤤԾʧͥŪ˻Ȥ碌DHCPФˤϡٱ򤹤뤳Ȥdz륵Фؤ䤤碌ᤤԾ餱򤹤롣

DHCP졼ȤλȤߤ򤹤䤬ΤǡҲ𤹤롣
H18NW44
DHCPѤͥåȥǡ졼ȤɬפˤʤΤϡͥåȥˤɤε郎ѤƤ礫

å󥰥ϥ֥֡å
ԡ롼

 򡧡

DHCP DiscoverξΥե졼๽¤
äȱΤǡ֤ľޤ
dhcp

եɤξܺ
RFChttp://tools.ietf.org/html/rfc2131Ȥ˺
FieldĹ
ʥХȡ
̣
op 1å饤ȤRequest1ФReply2
htype 1ϡɥ̾ΥͥåȤ1
hlen 1ϡɥĹ̾ΥͥåȤ6
hops 1hops̾0
xid  4Transaction IDϢ̿Ƕ̤ѤID
secs 20ޤϡвᤷÿ
flags 2ե饰֥ɥ㥹Ȥ׵᤹ϡֺΥӥåȤ1򤿤Ƥ
ciaddr  4饤ȤIPɥ쥹ǤIPɥ쥹äƤơRenewʤɤˤƼȤʤɤ˸ꤷƥåȤ롣
yiaddr   4your IP address ʧФIPɥ쥹åȤ 
siaddr  4 ư˻ȤμΥСDHCPФIPɥ쥹åȤ櫓ǤϤʤ
giaddr   4졼ȤIPɥ쥹
chaddr16ClientHardware addresClientMACɥ쥹
sname64ФΥۥ̾
file128
optionsvariableץDHCPΥ꡼ࡢ֥ͥåȥޥǥեGWDNSʤ

ǤϡºݤDHCPΥѥåȤ򸫤Ƥߤޤ礦
DHCP DISCOVER
饤ȤФõDiscoverˡMACɥ쥹FFFFFFFFFFFʤΤǡ֥ɥ㥹ȤǤ롣֥ɥ㥹ȥѥåȤϥ롼Ǥ˴뤿ᡢ롼ĶʤʤΤǡƱ쥻ǤΤDHCPѤǤ롣
dhcp_discover

DHCP OFFER
DHCPФΥ˥㥹ȡǥեGWʤɤξ碌Ƥ롣
ʲΥץξˤ192.168.1.2Ƥ졢ǥץΥ֥ͥåȥޥRouterʥǥեGWˤʤɤƤƤ롣
dhcp_offer2


DHCP REQUEST
饤Ȥλ롣֥ɥ㥹ȡ
4
֥ɥ㥹ȤΤϡ̿ˤäIPɥ쥹ȤΥС뤿Ǥ͡
ȤȤϡѥåȤˡIPɥ쥹äƤޤ͡
פäƤΤǤºݤˤäƤޤ󡣤ɤ顢transaction idİƤΤǤ礦Ϣή϶̤transaction idѤ롣idޤƤꡢɤIPɥ쥹ȤľܵܤƤʤ褦׳ǧ

DHCP ACK˥㥹
dhcp_ack

ͥåȥڥꥹȻβH25ǯNW孵2ˤǤϡʲεҤ롣
L2SWڤSWDHCP̡ԥ󥰵ǽѤ롣εǽˤäơL2SWڤSWϡDHCPФü֤̿DHCPå̲᤹ݡȤξޤƴƻ뤹롣ˡDHCPФIPɥ쥹Ƥ줿ü̿Ǥ褦ˡݡȤΥե륿ư椹롣

̡ԥ󥰤Ȥϡ֤ΤפȤ̣ǤĤޤꡢDHCPΥѥåȤΤ֥̿åޤŪˡDHCP̡ԥ󥰤εǽϰʲǤ

DHCPФ³ݡȤꤹ뵡ǽ
ꤷݡȰʳDHCPФ³Ƥ⡢DHCPʧФ򤵤ޤ󡣤⤷ꤷݡȰʳDHCP OFFERDHCP ACKϤȤƤ⡢Υե졼SW˴ޤ

DHCPФIPɥ쥹ƤPC̿뵡ǽ
DHCPΥѥåȤ򥹥̡ԥ󥰤DHCPIPɥ쥹ʧФ줿PC̲ᤵޤPCMACɥ쥹ǹԤޤˤϡѼԤ˸IPɥ쥹ƤPC̿ݤޤ
DHCP̡ԥ󥰤εǽ

CatalystǤDHCP̡ԥ󥰤Ҳ𤷤ޤ
SW(config)# ip dhcp snooping  DHCP̡ԥ󥰤ͭ
SW(config)# ip dhcp snooping vlan 10DHCP̡ԥ󥰤ͭˤVLAN
SW(config)# interface fastethernet0/24嵭
SW(config-if)# ip dhcp snooping trust
SW(config)# interface fastethernet0/1嵭
SW(config-if)# ip verify source port-security
­ޤϡDHCPФ³24֥ݡȤtrustʿꤵ줿ˤȤꤷޤ򤷤ʤݡȤuntrustʿѤʤˤȤˤʤꡢDHCPФ³ƤDHCPΥե졼ब˴ޤ
ϡDHCP̡ԥ󥰤IP Source GuardղäƤޤ1֥ݡȤǤϡüʳ̿ݤޤverifyפȤϡɤΤפȤ̣Ǥ


ݥ󥵡ɥ

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