Dhcp {dynamic Host Configuration Protocol}

— Spe cif y the UDP po rt num ber on wh ich dh cp d shoul d list en. The d efault i s por t 6 7. The D HCP s er ve r tran sm its r es pons es to the D HCP cl ients at a por t num be r one g reate r than the UDP po rt sp eci fie d. For exa mp le, if the de fault po rt 67 is used , the ser ver li sten s on p or t 6 7 for r eques ts

and r es pons es to the clien t on po rt 68. If a po rt is spe cifi ed he re and the DHC P relay agent i s used , the sa me po rt on which the D HCP r elay agent should li sten mu st be s pec ifie d. Ref er to Se ction 16. 2.4 DHC P Relay A gent fo r detail s. -f — Run the da emon a s a fo reg roun d pro ces s. Thi s is m ostl y used f or de bugg ing. -d — Log the DHC P se rver daem on to the standa rd er ro r des cr ipto r. This i s mos tly use d for de bug ging. If thi s is not s pec ifie d, the log i s written to /var /log /m es sa ges . -cf — Spe cif y the location o f the con fi guration f ile. The def ault location i s /etc /dh cp d.con f. -lf — Speci f y the locat ion of the lea se data base f ile. If a leas e databa se fil e al ready e xis ts , it i s ver y im po rtant that the s ame file be use d ever y ti me the DHC P se rve r is sta rte d. It i s str ongly r eco mm ende d that this opt ion only be u sed fo r de buggin g pur pos es on nonprodu ction ma chine s. The de fault locati on is /var /li b/ dhc p/ dh cpd.l ease s. -q — D o not p rint the entir e copy rig ht mes sa ge wh en star ting the daem on. 16. 2.4. D HCP R elay Agen t The D HCP Re lay Agent ( dhc relay ) allow s fo r the relay of DHC P and B OO TP r eque sts f ro m a s ubnet wit h no D HCP s er ver on it to one or m ore D HCP ser ver s on oth er su bnets.

When a D HCP cl ient reque st s info rm ation, the D HCP Re lay Agent f or war ds the re ques t to the li st of DHCP s er ver s sp eci fie d when the DHC P Relay A gent is star ted. When a DHC P se rve r retu rns a rep ly , the reply i s broa dca st or unica st on the netwo rk that sent the orig inal reque st . The D HCP Re lay Agent li sten s for DHCP reque sts on all inte rfa ces unle ss the inte rfa ce s are s peci fie d in /et c/ sys con fig /d hc relay wit h the INT ERF ACES di re ctive. To sta rt the DHC P Relay A gent , use the co mm and ser vice dh cr elay sta rt. Pr ev

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Dyna mic Ho st Configu ration Pr otoc ol (D HCP )

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Ne xt Configu ring a DHC P Client

Red Hat E nter pr ise Linu x 4: Sy stem Ad mini stra tion Guid e P rev

Chapt er 16. Dyna mic Ho st Confi guration Proto col ( DHC P)

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16.3. Confi gurin g a DHC P Client The fi rs t ste p for c onfi gurin g a D HCP cl ient is to ma ke s ure the k erne l rec ogni zes the netw or k inte rfa ce car d. Most ca rd s are r eco gnize d dur ing the in stallation p ro ces s and the sy ste m is con fi gure d to u se the cor re ct ke rnel mo dule fo r

the ca rd. If a ca rd i s adde d afte r installa tion, Kud zu [1] s hould r eco gnize it and p rom pt fo r the con fi guration o f the cor re spon ding k ern el mo dule for it . B e sur e to c hec k the Har dwa re Com patibi lit y Li st availab le at htt p: // har dwa re.re dhat .co m/ hcl /. If the netwo rk car d is not conf igur ed by the in stallation p rog ra m or Kudzu and you kno w whi ch kern el mo dule to load fo r it , r efe r to Chapte r 30 Ke rnel Module s f or deta ils on load ing ke rnel module s. To con figu re a D HCP c lient manuall y, mo dif y the /etc /sy sc onf ig/n etwo rk file to enabl e networ ki ng and the con figu ration f ile fo r each netwo rk devi ce in the /et c/ sys con fig /net wor k- scr ipt s dir ecto ry. In thi s di rect or y, ea ch devi ce sh ould have a con fi guration f ile name d if cfg -eth0 , wher e eth0 is the netw or k dev ice nam e. The /etc /sy sc onf ig/n etwo rk file s hould c ontain the follow ing line: NE T WOR KING=y es The NET WO RKING va riabl e must b e set to yes i f you want netw or kin g to s tar t at boot ti me. The /etc /sy sc onf ig/n etwo rk -sc rip ts /if cf g- eth0 file should c ontain the follo wing line s: DE VICE =eth0 BO OT PR OT O= dh cp ON BO OT =ye s A c onfi gurati on file is nee ded f or eac h devi ce to be con fi gure d to u se DHCP .

Other option s for the net wor k s cr ipt inclu de : DHCP _H OSTN AME — On ly use this o ption if the DHCP s er ver re quire s the cli ent to s pe cif y a ho stnam e bef ore r ecei ving an IP ad dr es s. (The DHCP s er ver dae mon in Red Hat E nter pr ise Linu x do es not su ppo rt this f eature. ) PEER DNS = , wher e i s one o f the fo llow ing: ye s — Modif y /et c/ res olv .conf wit h info rmat ion fro m the se rver . If using D HCP , then ye s is the de fault . no — Do not mo dif y /etc /re sol v.con f. SRC AD DR =, wher e is the spe cifi ed sou rc e IP ad dr es s fo r outgoing pa ck ets. US ERCTL =, whe re is one of the fo llow ing: ye s — Non-ro ot user s are allo we d to con trol thi s de vic e. no — Non-ro ot user s are not allo wed to cont rol thi s devi ce. If you pre fer using a grap hical inte rfa ce, r efe r to Chapt er 10 Netwo rk Configu ration f or deta ils on us ing the Netwo rk Ad mini stra tion Tool to confi gure a netwo rk inter face to use D HCP . Tip For advan ced c onfi gurati ons o f client D HCP

option s su ch as pr otoco l timin g, lease requi re ment s and reque st s, dyna mic D NS sup por t , alia se s, as wel l as a wi de var iet y of values to ove rr ide , pre pend , or appen d to client -s ide con fi guration s, r efe r to the dhc lient and dhc lient .con f man page s. Note s [1 ] Kud zu is a hard war e pro bing tool run at sy ste m bo ot time to dete rm ine what har dwa re has b een ad ded o r rem ove d fr om the sy ste m. Pr ev Configu ring a DHC P Ser ve r

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