LAN

[Ioannis Theodoridis]

Epeidi den ekshgeis sxedon katholou to ti theleis na kaneis me to topiko sou diktyo, einai ligo dyskolo gia ton kosmo na sou apanthsei sygkekrimena.

Syntomh ekdoxh:
Kat'arxhn opws lei kai o N.Dionysopoulos, tha prepei na arxiseis apo ton eksoplismo. Aytos kata genikh omologia tha prepei na apoteleitai tpoulaxiston apo treis ethernet kartes (poly pithano o Apple na thn exei enswmatwmenh), ena switch h hub 10/100 Mbit me toulaxisto 4 portes (amfibalw an breis me ligoteres an kai kapote eixa akousei gia 3-port switch 10/100 diathesimo sto Alpha Computers) kai 3 kalwdia UTP category-5 (patch cords). Ta kalwdia mporeis na ta breis etoima h na ta ftiakseis o idios an kai den sto synistw.
Kathe H/Y tha syndethei sto switch/hub me ena patch cord. Ayta gia th 'fysikh' syndesh.
Gia na syndeseis 'logika' ta PC me ton Apple dwse ip dieythynseis 10.0.0.1, 10.0.0.2 & 10.0.0.3 me netmask 255.255.255.0, se kathe mia antistoixa apo tis kartes diktyou twn PC kai Apple. Etsi epitygxaneis kai logikh syndesh sto epipedo IP diktyou. Gia na syndeseis ta pc kai ton apple se epipedo efarmogwn (file/print sharing, internet sharing klp.) tha prepei na deis ayta pou sou proteinei o Nikos.
An den bariesai mporeis na diabaseis th megalh ekdoxh.

Megalh ekdoxh (exontas pei kai ta parapanw, pare mia anasa kai proxwra..):
Prin ksekinhseis na eksetaseis ti theleis na kaneis me to topiko soy diktyo (opote kai tha deis an se endiaferei sygkekrimena to file/print sharing h to na sthseis ena topiko web server h to na moiraseis internet h kapoia allh efarmogh poy apaitei diktyo). Analoga me to ti theleis na kaneis prokyptei kai to ti sou einai aparaithto. 
Kat'arxhn tha prepei na katalabeis kapoia basika pragmata peri IP dieythynsiodothshs. Sygkekrimena, h morfh mias dieythynshs IP (ekdosh 4) apoteleitai apo tesseris 8-bit statheres (pairnoun times apo 0-255 sto dekadiko systhma) xwrizwmenes apo teleies, dhladh toy typou 'x.y.z.t', px. 10.0.128.236. Prokeitai sthn ousia gia mia stathera 32 bit.
Apo ekei kai pera, o tropos me ton opoio einai domhmena ta diktya typou Internet (basismena sto IP) den epitrepei na enwsoume olous toys H/Y (h diktyakes syskeyes genikotera) apeytheias se ena terastio 'epipedo' diktyo opou oloi blepoun olous amesa, xwris endiamesous stathmous. Kati tetoio den einai praktiko. Gia na to kanoume ayto tha eixame anagkh apo ena terastias isxyos kentriko kombo me ton opoio tha htan syndedemnoi oloi oi H/Y pou tha ithelan na epikoinwnhsoun metaksy tous. Gia kati tetoio (pou parousiazei plithos akseperastwn problhmatwn se ylopoihsh, me tis shmerines synthikes kai anagkes diadiktywshs) den tha eixame kan anagkh to IP. Tha mporousame na kanoume th douleia mas apla kai me to Ethernet (thee mou, ti efialths tha htan aytos..).
Gia ayto to logo (arxika toulaxiston) xrhsimopoiithike mia kathgoriopoihsh twn dieythynsewn, wste na mporoun aytes na dhlwnoun to diaxwrismo tou xwrou twn dieythynsewn se ypoxwrous kai tou Internet, se topika diktya. Gia na mporoun loipon dyo diktyakes (IP-enabled) syskeyes na 'doun' amesa h mia thn allh tha prepei na einai sto idio topiko diktyo, dhladh na exoun dieythynseis pou anhkoun ston idio ypoxwro dieythynsewn. Diaforetika tha xreiasteis mia endiamesh syskeyh h opoia onomazetai dromologhths (router) h opoia epikoinwnontas kai me ta dyo (h perissotera) diktya, kanei sthn ousia ton 'troxonomo'. Opws tha sou poun arketoi edw, kati tetoio mporei - se orismenes periptwseis - na kanei ena linux mhxanhma. Se polles periptwseis de, o rolo aytos mporei na syndyastei me pollous allous akoma. Alla ayta tha ta breis kalytera ekei opou sou proteinei o Nikos.
Oi kathgories twn dieythynsewn IP ws eixan arxika, einai oi ekshs (sygxwreste mou mikro-lathakia sta -1 h -2, ta exw ligo skouriasmena):
[x].[y.z.t]  => Class A. Edw mporeis na exeis mexri 255 ksexwrista topika diktya kai (2^24-2) diaforetikes diktyakes syskeyes (h alliws 'ip-kombous') mesa sto kathena.
[x.y.].[z.t] => Class B. Edw mporeis na exeis mexri (2^16-1) ksexwrista dikyta kai (2^16-1) diaforetikous IP kombous mesa sto kathena
[x.y.z].[t] => Class C. Edw mporeis na exeis mexri (2^24-1) ksexwrista dikyta kai mexri 254 kombous.
(Yparxei pleon kai class D alla den yparxei logos na mplekseis perissotero)
Enw o diaxwrismos aytos exei problepsei wste na einai amesa anagnwrisimo to se poio class anhkei mia dieythynsh, efeyrethike mia texnikh wste enas ypoxwros opws orizetai apo ta parapanw, na mporei na spasei peraiterw se ypoxwrous. Anaferomai sto gnwsto 'subnet mask'. Tha to deis me morfh paromoia me tis parakatw:
255.255.255.0
255.255.240.0
255.255.0.0
255.255.255.224, klp.
Prokeitai sthn ousia gia mia akomh 32-bit stathera h opoia syndyazomenh me thn IP-dieythynsh enos kombou (an thymamai kala me logikh prosthesh otan kai oi dyo times einai se dyadikh morfh) mporei na mas dwsei tis ekshs plhrofories:
1) se poio ypo-diktyo akribws anhkei o kombos (h IP dieythynsh tou ypo-diktyou kai poia einai h dieythynsh 'broadcast' )
2) mexri posoi komboi einai dynaton na briskontai se ayto to ypo-diktyo.
Gia na briskontai loipon oi diktyakes sou syskeyes sto idio topiko diktyo (wste na mh xreiasteis dromologhth) tha prepei na exoun katallhles dieythyseis IP kai bebaia to idio 'subnet mask', wste apo thn logikg praksh poy soy eipa na prokyptei to idio ypo-diktyo.
Telos epeidh sthn ekdosh 4 oi diathesimes eleytheres dieythynseis den arkoun gia olo ton kosmo, yparxoyn kapoies dieythynseis gia idiwtikh xrhsh. Peran tou periorismenou arithmou eleytherwn dieythynsewn, o logos poy xreiazomaste idiwtikes dieythynseis exei na kanei me thn eykolia poy parexoun na stithei ena idiwtiko diktyo (px. eswteriko etairiko diktyo h 'intranet' h spitiko diktyo) xwris na prosfygoume se kapoia arxh h provider gia na mas paraxwrhsei th xrhsh kapoioy eyrous monadikwn IP dieythynsewn, kati pou bebaia den einai xwris antitimo. Etsi dinetai h dynatothta epanaxrhsimopoihshs IP dieythynsewn ftanei oi komboi aytoi na mhn syndeontai ap'eytheias sto internet wste na prokaloun problhma sth monadikothta twn 'dhmosiwn' IP dieythynsewn, kai mesw sto eswteriko diktyo na mhn antistoixizetai parapanw apo enas kombos sthn idia IP dieythynsh. (Genika se oti akous yparxoun kai eksaireseis, alla opws sou eipa kai nwritera, as mhn mpleksoume parapanw ta pragmata..)
Gnwstes private dieythynseis einai px. toy typou : 192.168.x.y /255.255.255.z h 10.x.y.z/255.0.0.0. (Thewritika den se empodizei bebaia tipote na xrhsimopoihseis kai dieythynseis typoy 'public' ftanei na mh bgainoun ap'eytheias sto internet).
Gia na mporeseis twra na moiraseis mia syndesh sto internet (ara mia h perissoteres public dieythynseis, oi opoies synithws allazoyn dynamika-dhladh kathe fora poy syndeesai sto internet) sto topiko sou diktyo to opoio pithanotata tha xrhsimopoiei private dieythynseis, sou xreiazetai kapoios eksoplismos poy na mporei na efarmosei thn texnikh tou NAT: Network Address Translation (mporeis na to kaneis kai mesw ergaleia typou 'proxy', wstoso ekei exeis eidikes lyseis analoga me thn efarmogh px. http proxy, ftp proxy, klp). Ayth th douleia (ektos apo dromologhtes, hardware firewalls klp) mporei na thn analabei kai ena systhma Linux me katallhlo logismiko (blepe IP Masquerading pou sou egrafe o Nikos). An malista theleis na prostatepseis kai to topiko sou diktyo apo ekswterikes apeiles, tha to syndyaseis kai me ena firewall (den exw asxolithei me to IP Masquerading alla nomizw pws mporeis na to kaneis me to idio logismiko). Bebaia paromoia pragmata mporeis na kaneis kai se windows mhxanhmata alla me tous gnwstous periorismous..
Kanontas loipon ta parapanw to mhxanhma sou me private dieythynsh px. 10.0.0.2 mporei na bganei sto internet mesw ths puclic dieythynshs px. 212.94.174.19 thn opoia tha moirazeis sto topiko sou diktyo mesw NAT.
Twra gia na moiraseis px. arxeia apo to ena mhxanhma sto allo, den glytwneis, prepei na biabaseis ayta poy sou proteinei o Nikos..
Ayta ta 'oliga' kai elpizw na mhn koimithikes diabazontas..
An xreiasteis kapoia erwthsh h parapanw boitheia sth diathesh sou .. 
Giannis.


"Nikos_Apostolakis" <Nikos_Apostolakis at math.ucr.edu> wrote in message news:mailman.1054594983.15413.linux-greek-users at lists.hellug.gr...
> Geia hara,
> 
> Ti xreiazetai gia na kanw ena "local network"? Basika endiaferomai gia 
> dyo linux koytia kai ena Aple me OSX. Ti logismiko xreiazomai?
> 
> Eyxaristw gia thn opoiadhpote boh8eia.
> 
> Nikos