Instruction/ maintenance manual of the product SuperStack 3 3250 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.
An important point after buying a device 3Com SuperStack 3 3250 (or even before the purchase) is to read its user manual. We should do this for several simple reasons:
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If you already are a holder of 3Com SuperStack 3 3250, but have not read the manual yet, you should do it for the reasons described above. You will learn then if you properly used the available features, and whether you have not made any mistakes, which can shorten the lifetime 3Com SuperStack 3 3250.
However, one of the most important roles played by the user manual is to help in solving problems with 3Com SuperStack 3 3250. Almost always you will find there Troubleshooting, which are the most frequently occurring failures and malfunctions of the device 3Com SuperStack 3 3250 along with tips on how to solve them. Even if you fail to solve the problem, the manual will show you a further procedure – contact to the customer service center or the nearest service center
