Benutzeranleitung / Produktwartung SuperStack 3 3250 des Produzenten 3Com
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http://www.3com.com/ Part No. DU A1750-0BAA 01 Publ ished D ecembe r 2003 Su perSta ck ® 3 Swit ch 322 6 and S wit ch 3250 I mpl emen tat io n Gu i de 3CR1 750 0-91 3CR1 750 1-91.
3C om Cor poratio n 35 0 Campu s Dri ve Mar lboro ugh, MA USA 0175 2-3064 Copy right © 20 03, 3C om Cor poratio n. All ri ghts reserve d. No pa rt of thi s docu mentat ion may be reproduced in any f .
C ONTEN TS A BOU T T HIS G UIDE Conventions 10 Related Doc umentation 1 1 Documenta tion C o mments 11 1 S WITCH F EATURES O VERVIEW Wh at i s Ma na ge men t So f twa re ? 1 3 Swi tch Featu res Expl a.
Implem e n ting 802.3ad Aggregated Links 25 Aggregated L inks and Y our S witch 25 Aggregated Link — M anual Configurat ion Example 27 3 U SING M ULTIC AST F ILTERING Wha t is a n IP Mult ica st? 2 .
802.1D tra f fic c lassification 48 Dif fServ traf fic classi fication 49 IP Port tr affic c lassifi cation 50 T raff i c P r ioritization and your S witch 51 Li miting the Rate of a Port 52 T raff i .
10 M AKING Y OUR N ETWORK S EC URE Limiting Ma nagem ent Ac cess by IP Address 71 Securing Ac cess to the W eb Interface 72 Gett ing a Digital Certificate 7 2 Securi ng Access to the Command Line In t.
A C ONF IGU RA TIO N R UL ES Configuration Rules for Gigabit Et h er net 99 Configuration Rules for Fast E ther net 100 Configuration Rules w ith Full Duplex 101 B N ETWORK C O NFIGUR ATION E XAMPLES .
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A BOUT T HI S G UI DE This g uide desc ri bes the featu res o f the 3Com ® SuperS tack ® 3 Swi tch 322 6 (3 CR1 7500 -9 1) an d 3C om ® Supe rS tack ® 3 Swi tch 32 50 ( 3CR 17501- 91 ) . It o utlines how to u se the se fea tures to opti mize t he per forman ce of your net work.
10 A BO UT T HIS G UI D E Con ventions Ta b l e 1 and Ta b l e 2 list conventi o ns th at ar e u sed th ro ughout this guide. Ta b l e 1 Notice Icons Ic on Notice Ty pe Descri ption In fo rmat io n no.
Relat ed Docu mentati on 11 Related Do cum enta tion In a ddit ion t o this guid e, e ach Switch doc um ent at ion set incl ud es th e fo llo wi ng : ■ Super Stack 3 Swi tch 32 26 and S up erSt ack .
12 A BO UT T HIS G UI D E Pl ease incl ude the f ollowing in format ion when cont acting us : ■ Document title ■ Do cum ent par t n um be r ( o n t he t itl e pag e) ■ Page numb er (if approp ri.
1 S WITCH F EA T UR E S O VE RVIE W Thi s ch apter co ntain s introdu ctor y in forma ti on ab out the Sw itch m anag em ent software a nd supp orted f eatu r es.
14 C HAPTER 1: S WITCH F EATUR ES O VER VIEW Ag gregated Lin ks Aggr egated links are c onnection s that all ow devices t o communicate using mult iple l ink s in par allel. Y our Sw itch suppor ts o ne aggrega ted l ink using the two 10/100/ 100 0 and S FP po rts (25 -26 on t he Sw itch 32 25, 49-50 on the Switch 325 0).
S wit ch Fea tures Explai ned 15 Flow c ont rol uses b ack jamm ing on ports oper ating in ha lf d uplex mod e, and is implement ed using the IEEE Std 802.
16 C HAPTER 1: S WITCH F EATUR ES O VER VIEW ■ LACP autom atic aggr e gations — that is, LACP enabl ed on all po rts and th e aggreg ated l inks cr eated automatic ally . The aggr egated link shou ld be e nable d an d Span ni ng T ree P rotoco l ena bled.
S wit ch Fea tures Explai ned 17 ■ Enable o ne of the l ess ef fi cient pat hs if the m ost ef fi cient pat h fails. RSTP is an enhanced ver sion of STP (Spanni ng T ree Pr otocol) and is full y compati b l e w i th STP syst ems. RSTP c an r estor e a network co nnection qui cker than the legacy STP fe atur e.
18 C HAPTER 1: S WITCH F EATUR ES O VER VIEW manage ment applic ati on, the Swit c h can tr ansfer thes e statis tics to your wor kstatio n on reque st or when a pre-define d threshold is exceede d . For more in format ion about RMON and Event No tific ation, see Cha p t er 7 “ St atus Mo nito ring a nd St atist ics ” .
S wit ch Fea tures Explai ned 19 All cu rren tly l earnt addr esses o n the port are ma de permanent. Any packe ts co nt aining a sou r c e address n ot lear n t on t he po rt wi ll be droppe d. ■ Ne tw ork Log in Connecti o ns ar e only allowe d on a port on ce the clie nt has been authen ti cated by a RADIUS serv er .
20 C HAPTER 1: S WITCH F EATUR ES O VER VIEW.
2 O PTIM IZIN G B ANDWI DTH There a r e m any w ays yo u c an op timiz e the bandw idt h o n your net wor k and impr ove network pe rfor mance. If you utili ze cert ain Swit ch featur es yo u can prov.
22 C HAPTER 2: O PTIMIZING B ANDWIDTH a lin k do n ot supp ort au to-neg otiation, b oth e nds must be m anua lly set to fu ll d uplex o r h alf du plex a ccordin gly .
Ag g re g at ed Li nks 23 Ag grega t ed Lin ks Aggr eg ated links ar e connect ions tha t allow devi ces to communicate usin g multi p l e m ember links i n paral lel. Ag gr egat ed links prov ide the f ol lo wi ng be n efi t s : ■ They can potential ly i ncreas e the bandwi dth of a co n nec tion.
24 C HAPTER 2: O PTIMIZING B ANDWIDTH By de fau lt, LAC P is di sable d on a ll Swi tch ports. I f a memb er link i n an aggre g ated l ink fai ls, the tra ffi c usin g that link is dynamic ally r eassigned to the r emain ing member links i n the aggr egat ed li n k.
Ag g re g at ed Li nks 25 Imp lemen ting 8 02.3ad A ggrega ted Links LAC P can be enabl ed or disabl ed on a pe r por t basis. Y ou c an im pleme nt 802 .3ad aggregat ed links i n two ways: ■ Ma nual Agg rega tions — Y o u can man ually add an d remov e po rts to and fr om an aggr egate d link v ia Web command s.
26 C HAPTER 2: O PTIMIZING B ANDWIDTH ■ A member l ink port can only belong to one aggr egated lin k. ■ The me m ber link por ts ca n be mixed m e dia, t hat is f iber and/o r twist ed pai r por ts w ithin the sam e aggrega te d link. ■ The member l ink ports must have th e same conf iguration .
Ag g re g at ed Li nks 27 aggr egated li nk traf fic to th e rem aining port s. Aggr egated li nks ther efore provide built-i n resilience for y our netw ork. The Swit ch also h as a mechanism to p r event the pos sible occ urr ence of pa ck e t re -o rd er in g w h e n a l in k rec ov e rs t o o so on a ft e r a fai lu re.
28 C HAPTER 2: O PTIMIZING B ANDWIDTH 3 Con nect port 5 on the c ore Switch to por t 25 o n t he Sw itc h 3226 . 4 Con nect port 7 on t he up per Switch to por t 26 o n t he Sw itch 3 226 .
3 U SING M ULTIC AST F ILTERIN G Mul ticast filteri ng improves the p erfor manc e of net works that ca rry mu lt i ca st tr a f f ic. This c h a pter explain s multica sts, multica st filter ing, and h ow mult icast filter ing c an be im plem ent ed on yo ur Sw itch .
30 C HAPTER 3: U SING M ULTIC AST F ILTERIN G A multic ast pack et is iden tified by the pr esenc e of a multi cast gr o up addr ess in the de stinat ion addr ess fiel d of the pac ket’ s IP h eader .
Multi cast Filt eri ng a nd Your Swit ch 31 Figure 4 The ef fect of multic ast fil tering Mu l tic as t Filt er in g and Y our Swi tch Y o ur Switch prov ides a utoma tic m ul ticast filteri ng su pport using IGM P (Int erne t Grou p Ma nagem e nt P r o to col) Sn oopin g.
32 C HAPTER 3: U SING M ULTIC AST F ILTERIN G I GM P multicast f ilteri n g works as follows: 1 The I P route r (or querier ) peri odical ly send s qu er y packet s to all th e endst ation s in t he LA Ns or V LANs th at are co nnect ed t o it .
Multi cast Filt eri ng a nd Your Swit ch 33 wish to join or to which th ey alr eady belong. Th e querier i s always the dev ice with the lowes t IP addr ess in the subnetwork.
34 C HAPTER 3: U SING M ULTIC AST F ILTERIN G ro uter s on the su bnetwor k. Upon rec eivin g such a mess age, th e querier dete rmines whet her th at hos t is th e las t gr oup membe r on the subn etwo rk by issuing a group -sp ecific quer y .
4 U SING R ESILIEN CE F EA TUR ES Sett ing up resilience o n y our ne twor k he lps protect critic al link s agai nst failure, prote cts a gainst net work loops, and reduc es ne tw ork down time to a mi nimu m . The Switch p ro vides r e silient lin ks using the R apid Sp anning T r ee Pr otoc ol (RSTP ).
36 C HAPTER 4: U SING R ESILIENCE F EATUR ES The pr otoc ol is a pa rt of t he IE EE Std 802. 1 w- 200 1, bridge sp ecificat ion. T o ex plain RSTP more effec t ively , you r Switch will b e refer red to as a brid ge. Rapi d Spa nning T re e Pr oto col (R STP ) The Rapid Spann ing T re e ( RSTP) i s an enh anc ed Spannin g T r ee featur e.
What is STP? 37 As an e xamp l e, Figure 5 show s a network con taining three LAN segme nts separat ed b y three brid ges. W it h thi s co nfig uration, e ach seg ment can c omm uni ca te wi th t he othe r s u si ng t wo pat hs . Wit hou t S TP en ab led , th is conf igurati o n cr eates loo ps that ca use the netwo rk to ov erload.
38 C HAPTER 4: U SING R ESILIENCE F EATUR ES I f a link failur e is detecte d, as shown in F igure 7 , the S TP pr oces s rec onf i gu res t he ne t wo r k s o t ha t tr a ffic fro m LA N s eg me n t 2 fl ow s through Brid ge B.
How STP Wor ks 39 ■ Each port to have a cost . This spec ifi es the ef fi ciency of ea c h lin k, usuall y de termi ned b y the ba n dwidt h of t he l ink — the higher the cost , th e l ess ef fici ent the li n k . Ta b l e 3 sh o ws th e de f a ul t po rt co st s fo r a Swi tch.
40 C HAPTER 4: U SING R ESILIENCE F EATUR ES brid ge is c onf igured to fo rward traffic o nly betwee n its Root Por t a nd th e Desi gnate d Bridge Por ts fo r the respec tive n e twork se gm ents. A ll oth er ports ar e bloc ked, which means that t hey ar e prev ented fr o m r eceiv ing o r fo rw ard in g tr affi c.
How STP Wor ks 41 Figure 8 Port costs in a ne t work ■ Bri dge A has the l owest Brid ge Ident ifier in the netwo rk, and has ther efor e been selec ted as th e Root Bridg e. ■ Becau se Brid ge A is the Ro ot Brid ge, it is also the Desig nated Brid ge for LAN seg ment 1.
42 C HAPTER 4: U SING R ESILIENCE F EATUR ES ■ the r o ut e through Brid ges C a nd B cost s 20 0 (C to B =1 00, B to A =1 00) ■ the rout e through Bridge s Y a nd B c ost s 300 ( Y to B=2 00, B to A =1 00). Port 2 on Brid ge C is th erefor e selec ted as th e Designated Bridg e Port fo r L AN S eg m e nt 3.
How STP Wor ks 43 Figure 9 STP configur ations.
44 C HAPTER 4: U SING R ESILIENCE F EATUR ES Using STP on a Net work with Mu ltip le V LAN s The IEE E Std 8 02 .1D, 1998 Edit ion does not t ake into account V LANs when it c al culat es STP inform ation — the c alcula tions ar e only p erfor med on the basis of physical conne ctions.
5 U SING THE S WITCH D ATA B AS E What is the Sw it ch Dat abase ? The Swit ch Database is used by th e Switch to determin e wher e a packe t shou ld be fo rwarded to, an d w hich por t shoul d tran smit the pac ket if it is to b e forwar ded.
46 C HAPTER 5: U SING THE S WITCH D ATAB ASE Swit ch Da tabase En tr y Sta te s Da ta b as es en tr i es c an ha ve th ree s ta t es : ■ Lear ned — The Swit c h has plac ed the ent ry into the Swit ch Databas e when a pac ket was r ec ei ved fr o m an ends tatio n.
6 U SING T RAF FIC M ANAGE MENT Using t he t raffic man a gement c apabi lities o f your S wi tch al lows your net work tr affic to b e controlle d and prio ritized t o ensu r e t hat high pr io ri ty da ta i s tr a ns m it ted w i th mi ni m u m d el a y .
48 C HAPTER 6: U SING T RA F FI C M ANAGEMENT ■ Fin ancial ap plica tio ns — Use d b y Ac co unts de par tment s tha t ne ed i mmed i ate acc ess to l arge fi les and sp read sheets.
Ho w Traf fi c Pr io r iti za ti on W ork s 49 The 80 2.1D s tan dard spec ifie s eig ht di stinct le vel s o f prior ity (0 t o 7 ), each of wh ich relates to a part icular type of traffic. The pri ority leve ls and th e ir t ra ffic ty pes a re s ho wn i n Fi gu re 11 in order of increas ing p rior ity .
50 C HAPTER 6: U SING T RA F FI C M ANAGEMENT Figure 12 D SCP Se rvice Le vel Mapping Figu r e 1 2 illust rates how Diff Serv code poin t (DSCP) servic e levels ar e mapp ed t o the four traffic que ues.
Tr af fi c Pr io ri ti za ti on an d yo u r Sw itc h 51 Figure 13 IP Port Mapping Figu r e 1 3 il lustra tes h ow IP port num ber s are ma pped to the four traffic queu es. T raf fic P ri oriti zation and y our S witch Y o ur Switch sor ts tra f f ic b ased on Class of Service .
52 C HAPTER 6: U SING T RA F FI C M ANAGEMENT 802 .1D pa ck ets are c a te go ri ze d in to th e e ig ht t r affi c c l as se s d e fi ne d by I EEE 802.1D; th e hig her the cl ass the hi gher the pri o rit y giv en to the pac ket on trans missio n. See Figure 1 1 .
Li m iti ng th e R a te o f a Po rt 53 Co nfigur in g rate l imiti n g Rat e limitin g ca n be c onfi gured on y our Swi tch usin g t he Web interfac e or t he Com mand Lin e Inter face (CLI). Rat e limitin g ca n be ap plied in step s of 1 M b on 1 0/100 p or ts and i n step s of 8 M b on 1 0/1 00/1 000 port s.
54 C HAPTER 6: U SING T RA F FI C M ANAGEMENT.
7 S TA TU S M ONITORIN G AND S TA TIS TICS This ch apter cont ain s detai ls of the Rem ote M o nito ring ( RM O N ) feature that assi sts you with status m onit oring a nd stat istics.
56 C HAPTER 7: S TATUS M ONI TOR I N G AND S TATISTICS Statistic s The St atist ics gr oup pr ovi des traf fic an d erro r stat isti cs showing p ackets, bytes, b roadca sts , mul ticast s and errors on a LAN segme nt o r VLA N.
B enefits of R M ON 57 Bene fits of RMO N Using the RMON featur es of yo ur Switch has thre e main adva ntages: ■ It im proves you r efficie nc y Using R M ON allows you to r e m ain a t one wo rkstati on an d c ollect inform ation from wide ly disp ersed L AN segm e nts or VLANs.
58 C HAPTER 7: S TATUS M ONI TOR I N G AND S TATISTICS When usi ng the RM ON feat ures of the Switch , no te t he f ollow ing: ■ After the defa ult sessions are created, t hey hav e no special sta tus. Y ou can delet e or ch ange t hem a s r eq ui r e d .
8 S E TTI NG U P V IRTUAL LAN S Setti n g up Virtual L ANs (V L ANs) o n your Switch incr eases th e ef ficiency of y our ne t wor k by di vi ding the LAN in to l og ica l, ra th er tha n ph ysi cal , segm ents whi ch are eas ie r to manage.
60 C HAPTER 8: S ETTING U P V IRTUAL LAN S Figure 14 A network setup showing thr ee VL ANs Benefit s of VLANs The main benef it of VLANs is that th ey pr o vid e a n e twork seg m ent ation sys tem that is far more fle x ible than any trad iti onal network.
VLAN s and Your Swit ch 61 ■ VLANs help to c ontrol traf fic W ith tradi tio nal ne two rks, c on gestion can be cau sed by broadc as t tr affi c tha t i s d ire ct e d t o al l ne tw o rk d ev ic e s w h et he r th ey re qu ire i t or not.
62 C HAPTER 8: S ETTING U P V IRTUAL LAN S Figu r e 1 5 sh ows a ho w a Lay er 3 switch can be used to route bet ween VLAN s o n the sw it ch an d ho w an a dd itional VLAN ca n be used to aggr egate two VLANs.
VLAN s and Your Swit ch 63 Figure 16 T wo VLANs con nected via a l ayer 3 swit ch Cr eatin g N ew V LANs If yo u wa nt to m ove a port f rom t he De fau lt VLA N to a nothe r VL AN, yo u mu st first de fin e info rmati on about t he ne w V LA N on your Sw itch .
64 C HAPTER 8: S ETTING U P V IRTUAL LAN S T o carry m ult iple VLANs acr oss a single physi cal (bac kbone) link, each pac ket must be t agged with a VLAN ident ifi er so that th e Switch es can ident ify whic h pack et s belong i n wh ich VLA Ns. T o com mu nicate be tw een VLANs a router m ust be use d.
VLAN Confi gurati on Exam ples 65 T o s et up t he c o nf ig ura ti on s h own in F igure 17 : 1 Configu r e the VLAN s Define VL AN 2 on t he S wit ch. VLAN 1 is th e defaul t V LAN and a lread y exist s. 2 Add ports to the VL ANs Ad d po rt s 10 , 11 a n d 12 of t he Sw it ch a s un ta gg ed mem ber s t o VL AN 2.
66 C HAPTER 8: S ETTING U P V IRTUAL LAN S.
9 U SING A UTO M AT IC IP C ONFIGURATIO N This c hapter ex p lain s mor e about I P addre sses and how the auto matic conf igurati o n opt ion works . It co vers the fo llowin g topi c s: ■ How Y ou.
68 C HAPTER 9: U SING A UTOMA TIC IP C ONF IGU RATI ON How Aut oma ti c I P Con fi g uration Wor ks Wh e n you r Sw i t ch is p ow e re d u p fo r th e firs t t im e th e IP co n fi gu ra t io n setting is set to auto — th is is the d e fa ul t s e tti ng .
Imp ortant Consi derat ions 69 I f you want DHCP to be th e method fo r autom atic con figurat ion, make sur e that y our DHCP ser vers ar e op er ating normally befor e you power on yo ur Swit ch.
70 C HAPTER 9: U SING A UTOMA TIC IP C ONF IGU RATI ON.
10 M AKI NG Y OUR N ETW O RK S ECU R E This c hapter o utlines the Port Secur ity and Swit ch Management Login featu res , ex plains the key benefi ts of usin g these featu res , and giv es examp les o f how an d w hy yo u w o uld use t hem in your net work.
72 C HAPTER 10: M AKING Y OUR N ETWORK S ECURE inter face of th e S witch using con sole port , even if yo u ha ve denie d al l acc ess t o the S witch u sing th e trust ed I P feat ure. Secu rin g A ccess to th e Web Int e rfac e The Switc h 3226 and Switch 3250 support HTTPS, allowing sec ur e acc ess to the Web in te r fa c e of th e Sw i t ch.
Securi ng Access to the Co m mand L ine Inter face 73 has not been c e rtifie d by a Certif icate Authori ty (CA) but securit y will no t be ot her wis e affect ed. If you c anno t g ene rate a n X.50 9 c ert ificate you rself, you ca n buy on e from one of the Cer tifying Aut ho rities or you r ISP .
74 C HAPTER 10: M AKING Y OUR N ETWORK S ECURE A m aximu m o f 32 a ccess lists can b e appli ed u nder the c ur r e n t oper ating system. A ccess list ru les can be a pplied and tr af fic is f orwarded at wire speed u sing l ayer 3 d estinat ion IP a ddresses and netw ork p orts .
What is Netw ork L ogin? 75 the po rt. The sour ce M AC addre s s in r eceived packets is used to de t erm in e t h is ; a l l tr a ffic from ot h er n etw o rk d e vi ce s i s f il t ered . What is Net w or k Login? Ne two rk Logi n con tr ols u ser a cce ss at the n etwo rk edg e by bl ocking or unb locking ac cess o n a p er -po rt basis.
76 C HAPTER 10: M AKING Y OUR N ETWORK S ECURE Swi tch, as shown in Figu re 1 9 . The Switch does not int erpr et or stor e t his in fo rm a ti on. Figure 19 Ne twork Login Operation When the clie n t.
Wh at is Swit ch Mana gement Logi n? 77 ■ The RA D IUS serve r in y our netw ork is oper ation al. ■ If the RA DIUS ser ver fails or is una vaila ble, cl ient devic es wil l be unab le to acc es s th e n etw o r k. ■ Netwo rk L ogin is not sup ported on p orts conf igured to opera te as members of a n aggr egated lin k.
78 C HAPTER 10: M AKING Y OUR N ETWORK S ECURE manage able net work devi ce is a commonpl ace securi ty measu re. If th e l ocal Switch databas e is enab led, th e network ad m i nistra tor must hav e l ocal access t o each Switc h to secur ely chan ge user name an d pass wor d i nfor mat io n.
Wh at is Swit ch Mana gement Logi n? 79 Figure 20 RA DIU S A uthe nt ication O peration Impor tant Con sidera tio ns This sec t ion contain s some importan t co n si d erati o ns when using RADIUS aut hent ication of S witch M anage men t Logi n on the S wi tch 3 226 and Sw itch 32 50.
80 C HAPTER 10: M AKING Y OUR N ETWORK S ECURE What is RA DIUS ? R emote Authent icatio n Dial-I n User Serv ice (RADIUS) is an i ndustr y stan dard protoc ol for carryi ng aut hentic ation , aut hori zatio n and conf igurati o n in formati o n b etween a netwo rk devi ce and a shar ed auth enti catio n serv er .
11 IP R OUTIN G Rou ting is a me thod for dist ributing traffic th r o ugh out a n IP ne two rk. It is used to joi n LANs at the ne twork lay er (Lay er 3) of t he Open System s Interconne ction (O SI) mode l. A r o uter p rovides b ot h fi ltering and brid ging funct ions across the ne twor k.
82 C HAPTER 11: IP R OUTIN G W ha t is R out ing ? Rou ting di stribute s pac kets ov er pot ential ly dissimi lar n etwork s. A ro uter i s t he devic e that acc ompli shes thi s task. Y o ur Swi tch, as a L ayer 3 devi ce, can act as a r o ute r . Rout ers typi cally : ■ Connec t network s.
What is IP Routi ng? 83 Wha t i s IP Rou ting? An IP ro uter , u nlike a bridg e, oper ates at th e network layer o f the OSI Ref er enc e M odel . The ne two rk la yer i s also re f erred to as Layer 3. An IP ro uter ro utes packet s by examining th e network lay er addr ess ( IP address).
84 C HAPTER 11: IP R OUTIN G Benefits of IP Rou ti n g IP rout ing provi des t he follo win g feat ures and bene fits: ■ Econ om y — Be cau se yo u can co nnec t sev eral se gmen ts to t he sa me .
IP Ro ut ing Concept s 85 Figure 23 Rout i ng Interfaces Routi ng T able s W ith a routing t abl e, a rou ter or host de term ine s ho w to se nd a p ack et tow ar d its ulti mate destinat ion. T he r o ut ing t able contai ns an entry fo r ever y le arne d and loc ally define d netw ork.
86 C HAPTER 11: IP R OUTIN G Ro ut in g ta bl e dat a is u pda t ed st ati cal l y or d yna mi c al ly : ■ Statical ly — Y ou man ually ent er st atic r outes in the r outin g table.
Mu lti ple IP Inte rf ace s per VLA N 87 This m odel allo ws the Switc h to r oute th e pac ket fir st, and then if t he pack et ca nno t be rou ted, g ive the pac ket to Laye r 2 to be bridg e d by the VLAN . Th is sche me give s you the f lexi bility t o d efine rou ter interfac e s on top of sev eral br idge po rts.
88 C HAPTER 11: IP R OUTIN G Im ple me nt ing IP Rou ti n g T o r oute ne twork tr af fic us ing IP , yo u mu st perform these task s i n the followi ng order : 1 Conf ig ur e V L ANs . 2 Establi sh IP nterf aces o n t hose VL ANS . Co nfigur ing I P V LANs If you want to use IP routing, yo u must first c onfigure th e VLAN t o u se IP .
Implement ing IP Routi ng 89 De fining a n IP In terf ace After y ou decide t he VLAN index, I P addre ss, and su bnet mask fo r each IP i nterface y ou want to cr eate, you can def ine each in terfac e using t he Command Lin e Interfac e or the Web inter face.
90 C HAPTER 11: IP R OUTIN G ■ Stati c routes take pr ecedence over d ynamic ally learned r outes t o the same d estinatio n. ■ Stat ic routes are incl uded in per iodi c R IP upda tes se nt by yo ur Laye r 3 Swit ch .
IP Ro ut ing Proto cols 91 Ro uter Mode The av ailabl e setti n gs fo r r o uter mode are as foll ows: ■ Di sabled — The Swit ch ignor es all inc oming RIP packets and does not gener ate any RIP pac kets of i ts ow n. ■ Enab led — The Swit ch b roadcasts RIP u pdat es and p r o cesses inco ming RIP pack et s.
92 C HAPTER 11: IP R OUTIN G ■ RIPv1 – Rout e info rmati on is broad cast p eriod ically to o ther routers o n the ne two rk usin g the a dve rtiseme nt list fo r RIP-1 u pda tes. ■ RIPv2 – Rou te inf orma tio n is mu lticast perio dical ly to ot her r out ers o n the netwo rk u sing t he m ulticast address o f 2 24.
IP Ro ut ing Proto cols 93 Adv erti s ement A ddr ess The Swit ch uses the adver tisement ad dr ess to advertise r outes t o other st ations on the same network. Eac h inte rfa ce that you def ine uses a dir e cted br o adc ast a ddres s as the adver tisement a d dr ess.
94 C HAPTER 11: IP R OUTIN G networ k. UDP packe ts that r ely on the BOOTP r elay a gent ar e mo dified and th en f orwarded throug h the router . ■ Dy na m ic H o st C o nfi gur ati on P rot oc ol (D HC P ) A ho st ca n retrie ve its own c onfi guration i nform ation incl ud ing IP addr ess, fr om a DHCP ser ver thr o ugh the I P n etwork.
IP Ro ut ing Proto cols 95 Figure 25 Example of an ARP C ache If the IP a ddress doe s n ot ha ve a cor respon ding MA C add r ess, the ho st or ro uter br oadcasts an A RP reques t packet t o all th e devi ces on the networ k. The ARP r equest contain s info rmatio n about th e target and sou rce add ress es for th e prot ocol (I P addre sses).
96 C HAPTER 11: IP R OUTIN G Figure 27 Example of ARP Ca c he Updated wi th ARP Reply After t h e MAC addr ess is known, th e host or ro uter can send the pac ket directly to th e ne xt ho p. AR P P r ox y ARP proxy a llow s a host tha t has no routi ng abil ity to det ermin e the M AC address of a h ost on an oth er ne twork or su bnet.
Ad vanced IP Routi ng Opt i o ns 97 Figure 28 ARP P r ox y Int ernet Contr ol M ess age P rotoc ol (ICM P) Becau se a router kno w s o nly about the next n etwo rk hop , it is n ot awa r e of prob lems that m ay be closer to th e destina tion. D e stinat ions m ay be unreach able if: ■ Ha rdw a re is te mp o r ar ily o u t o f s erv ic e.
98 C HAPTER 11: IP R OUTIN G.
A C ONFIGURATIO N R ULES Con fi g uration Rules fo r Gi g ab it Eth e rn et Gigab it Eth er net i s desi gned to ru n ove r seve ral med ia: ■ Singl e-m ode f iber o ptic ca b le, w ith conn e ctions up to 5 km (3.1 miles). S up port for d istances o ver 5 km is supp or ted de pendin g on t he module spec ificat ion.
10 0 A PPENDIX A: C O N FI GUR A TI ON R ULES Con fi g uration Rules fo r F ast Et her ne t The t opo logy rul es f or 100 Mbps Fa st Ether net are slight ly different t o those for 10 M b ps Et herne t. Fi gur e 29 i ll ustrate s the k ey topolo gy r ules and pr ov ides exampl es of how they allow for l arge-scale F ast Ethernet net works.
Confi gur ation Rules for Fast Ethe rnet 101 ■ A tot al ne twork span of 325 m ( 106 6 ft) is allow ed in singl e-repeater topol ogies ( one h ub st ack p er wi ring cl os et with a f iber li nk to the co llapsed back bo ne).
10 2 A PPENDIX A: C O N FI GUR A TI ON R ULES.
B N ET WOR K C ONFIGURATI ON E XAMPLES T hi s c h ap te r co n t ai n s th e fol lo w in g s e ct io n s: ■ Si m ple Net w or k Configurat ion Exampl e ■ Deskt op Switch Example ■ A dva nced Ne .
10 4 A PPENDIX B: N ETWORK C O N FI GUR A TI ON E XAM PLE S S imple Netwo rk Con fi g uration E xamp le The f ollo wing i llustr ation show s h ow t he Sw it ch 3 226 a nd Switch 325 0 can be used in your ne two rk.
Advan ced Net work Confi gurat ion E xample 105 Ad va nced Ne twor k Con fi g uration E xamp le The followi ng illust ratio n sho ws a n etwork examp le th at illu strates how yo u can set u p your net work for o ptim um pe rforma nce using som e of the features suppor ted by y our Sw itch.
10 6 A PPENDIX B: N ETWORK C O N FI GUR A TI ON E XAM PLE S.
C IP A DD R ESSING This ch apter prov ide s som e backg r ound de tail on th e IP inf or mat ion tha t needs to be assi g ned to your Swit ch to ena ble you to man age it ac ro ss a net work.
10 8 A PPENDIX C: I P A DDR ESSI NG 192 .168.10 0. X (w here X is a nu mber be tw een 1 an d 254) w ith a su bnet mask 25 5.2 55.2 55. 0. These s uggest ed IP addre sses are part of a group of I P address es that have b e en set asid e speci ally fo r us e “in h ouse” only .
IP Ad dre sses 109 ref erre d to as a fie ld or an octe t . D ecima l no tat ion co nv ert s th e val ue of each field i nto a deci mal number , and the fi elds ar e separat ed by dots. Figure 33 D otte d Dec imal No tati on for I P Add resse s The deci m al valu e of an octe t wh ose b its are all 1s is 2 55.
11 0 A PPENDIX C: I P A DDR ESSI NG Subne ts and Subnet Masks Y o u can di vide yo ur IP n etwor k into sub -netw ork s also known as subn ets. Supp ort for sub nets is imp or tant bec ause the nu mber of bi ts a ssigned t o the dev ice p art of an IP addr ess limit s the num ber of devi c es t hat may be addr essed on any given net work.
Sub nets and Subn et Masks 111 As sho wn i n this e xam ple, t he 32 bits of a n IP addr ess a nd subnet m ask are u sually written using a n i nteger sh ortha nd. T his n otation t ran slates f ou r c on se c ut iv e 8- bit gr o ups (oc te t s) i nt o f ou r i nt ege rs t ha t r ang e f r om 0 thro ugh 255 .
11 2 A PPENDIX C: I P A DDR ESSI NG The su bnet mask 255.2 55.255. 255 identifi es a specific host. Th e IP addr ess 25 5.255.25 5.2 55 is r ese rved as th e de fault br oad cast addre ss. D e f aul t G a te w ay s A gate wa y is a de vic e on you r ne two rk wh ich is used to fo rward IP pac kets t o a remote d esti nation.
D A DV AN CE D IP R OUT IN G C ONCEPTS This ch apter provi des som e addi tiona l backgrou nd detail on the IP inform ation th at ca n be assi gne d to y our S witc h to en ab le you to ma n age i t acr oss a network. The se ar e a dvanced feat ur es and are not re quire d for oper ating yo ur sw itch in yo ur ne tw ork.
11 4 A PPENDIX D: A DVANCED IP R OUTI NG C O NCEPTS maint enance an d the risk of crea ting err oneo us add resses un l ess y ou plan t he a d dr es si ng sch eme pr op er ly .
Su pernet ting 115 ro uti n g table en tr y . (See R FC 1519 for d etai led info rmati o n about Super netti ng.) T o d o thi s, supe rnet addressing doe s some thing v ery different from t ra di t iona l TCP /I P r out in g ( wh ic h all ows on ly o ne net ma sk per net wor k) .
11 6 A PPENDIX D: A DVANCED IP R OUTI NG C O NCEPTS sup er net twic e as large. So, a supernet compo sed of 8 Class C networks would a ctua lly have 3 zeroes (8 = 2 3 ). This w ould seem v ery limited si nce it restricts you to usi ng grou ps tha t nicel y fi t into a pow er of 2 (1 , 2, 4, 8 , 16 .
Su pernet ting 117 Figure 37 Selecting a Range of A ddr esses Sup er net Exam ple The f our ne tw orks in Figu re 38 are all c onnec ted to th e same In ternet ser vice pr ovi der (ISP) . The I SP has decid ed to use supernett ing to re duce the size of the rout ing ta bles a nd improve through put.
11 8 A PPENDIX D: A DVANCED IP R OUTI NG C O NCEPTS ■ Super net 3 requires 7 Class C address spac es. Since 7 isn't a powe r of 2, we h a ve t o round i t up to e ight. This gives i t a netma sk of 255 .255.24 8.0. ■ Supernet 4 is a sin gle Class C netwo rk, making it ’ s netmask 255 .
G LOSSARY 3Com N etwo rk Supe rv isor The 3C om ne twork m a nageme nt ap plica tion use d to mana ge 3Com ’ s net working solut ions. 10 BA SE - T The IEE E speci ficati on for 10 M bp s Eth er net over Ca te gory 3, 4 or 5 twist ed pa ir cable . 1 00BA SE-F X The I EEE specific ation f or 100 Mbps Fast Ethernet over fibe r -opt ic cable.
120 G LOSSARY b andwi dth The in format ion ca pacity , measur ed i n bits per sec ond, th at a channel can tra nsmit. Th e bandw idth o f E the r net is 10 Mbps, the bandw idth of Fast Ether ne t is 100 M bps, and the b andwi dth o f Gigabi t Eth er net is 1 000 M bps .
12 1 device s tran smit simultaneou sly , a collisio n occurs and the coll id ing devic es de lay the ir retransm issions f or a random len gth of time .
122 G LOSSARY FT P File T ransfer Protocol . A protoco l based on TCP/IP for r el iable file tran sfer . fu ll du plex A s y ste m th at a l l ow s p ac ket s t o b e tr a ns mi t ted an d re c ei v ed a t the same t ime a nd, in effect, doub les the pot ential t hroughpu t o f a link .
12 3 IEE E St d 802.1w -2001 A stan dar d that d efi nes Rapid Spann ing T r ee Proto col (RSTP) behavio r . IEE E Std 8 02.1 X-2001 A sta ndard that def ines por t-based net work access c ontrol be hav ior . IE TF Inter ne t Engi neering T a sk Fo r c e.
124 G LOSSARY LAN Local Area Ne two rk. A net work of en dstation s (suc h as P Cs, prin ters, ser vers) and network d evic es (hubs an d switches) that cove r a rel ativel y small geog raph ic area ( usually n ot larger than a flo or or buildi ng) . LAN s ar e charac te rized by high tr ansmission speeds over short distances ( up to 10 00 m ).
12 5 mu lt ica st A pa cke t sent t o a sp ecific group of e nd stations on a ne twor k. mu ltic ast fi lterin g A sy st em that allows a network devi c e to on ly forwar d mult icast tr affi c to an en dstation if it has r egister ed that i t would li ke to r eceiv e th at tr affi c.
126 G LOSSARY RIP Rou ting Info rma tion P r o tocol. A n I nte rior G atew ay Prot ocol for TCP /IP networ ks. RIP uses di stanc e-vector algorit hms (DV A) to calc ulate least-h ops r out es to a de stinati on.
12 7 SS L Se cure Soc kets L ayer . A pro tocol use d fo r en crypt ing netwo rk t raffic. I t i s co mmonly used to en crypt HTTP t raff ic bet ween and br owser and a We b s e rv er . st andby port The port in a resi lient lin k that t akes over data tr ansmissi on if the mai n po rt i n the li nk fails .
128 G LOSSARY uni cas t A pac ke t sent t o a sing le en dstation on a ne twork. V ari able Le ngth Subne t Mas k (VLSM ) A suf f ix to an IP addr ess t hat indi cates th e size of t he subnet th at cont ains it.
I NDEX 129 I NDEX Numbers 802 .1D pr io rity level s 48 tr af fic clas sifi ca tion 48 A Acc ess Contr ol List s 73 add res ses clas ses 109 IP 88, 107 adver t ise RI P mo de 91 a dve rt is em en t ad.
13 0 I NDEX I ICM P (Int ernet Cont rol Mess age P rot ocol) de scri ption 97 loca tion in OSI Refer ence Mod el 83 IEEE St d 802.1Q-1 998 61 IEEE St d 802.
I NDEX 131 R RADIUS 77, 80 authen ticat ion 77 Rap id Spann ing T re e Pr otocol (RSTP) 16, 3 6 reg ister ed IP addr ess, obt aining 108 Remot e Monito ring.
13 2 I NDEX.
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