Merikes dieukriniseis parakalo!

[Richard Anderson]

Filippos Slavik <fsla at forthnet.gr> wrote in
news:mailman.1615.1109340679.375.linux-greek-users at lists.hellug.gr: 

> On Thursday 24 February 2005 21:28, Richard Anderson wrote:
>> Den einai akrivos linux erotiseis alla i have to ask them so to
>> understand:
>>
>> 1) Episis DEN exo vgalei akri genikos! An den orisoume sto
>> configuration utility tou adsl modem/router poia mac address tha
>> parei poia specific ip address tote einai san na leme tou adsl
>> modem/router oti kathe fora pou einai na apodosei ip addresses na
>> apodidei opoia ip address thelei se opoia NIC thelei ,diladi opoia ip
>> address thelei se opoio pc goustarei apo auta pou einai connected
>> pano tou! Auto omos DEN mou fainetai kai toso kalo. Den tha eprepe to
>> kathe pc sto lan na exei mia sygekrimeni static ip address i opoia
>> tha ginentai kathe fora applied stin Nic tou? 
> 
> Kai to ena alla kai to allo boleuei. Se kapoies periptwseis 8eleis na
> dineis IPs apo kapoio pool se hosts xwris na eksetazeis poia h MAC
> tous, allwte 8eleis na dineis sygkekrimenes IPs se sygkekrimenes MAC,
> allwte 8eleis na dineis IP mono se hosts pou gnwrizeis ths MAC tous,
> klp, klp. 

KATARXAS OI APANTISEIS SOU HTAN KATAPLHKTIKES & KATATOPISTIKOTATES & 
PRAKTIKOTATES!!! Perigrafoun toso kala to thema pou me afisan *only* with a 
couple of more extra description questions se sxesi me tis erotiseis pou me 
afinoun alles allou yfous apantiseis. :-)

Loipon,

a) Giati na thelo na doso sygektimeni ip address se sygekrimeni NIC hence 
se sygektrimeno pc? 

Mipos epeidi thelo to sygekrimeno pc na trexei epi monimou vaseos enan web 
server ie. ton Apache therefore tou xreiazetai i standard ip address etsi 
oste na xerei o adsl modem/router se poio specific host/port na kanei 
forward ta paketa tou "exo" kosmou allios o router (an allaze i ip address 
tou mixanimatos pou trexei ton web server ) den tha ixere pou na kanei 
forward ta paketa kai isos ta estelne se kapoio allo asxeto pc, pou 
endexomenos na eixe stin request web page phase tin ip address pou eixe 
proigoumenos to "real" web server pc? :-)

Diladi in other words allos perimenei ta requests kai allos ta 
paralamvanei? Kati san allos exei to onoma kai allos tin xari ? :-)

b) Giati na thelo na doso ip address mono se hosts pou gnorizo tin MAC 
address tous? Pou tha me exypiretouse kai tetoio? Mipos epeidi kapoios 
epitideios pigaine kai exone to pc tou kryfa se ena lan, to ethete se auto-
obtain mode, kai meta me tin seira tou o adsl router to pairnouse gia ena 
apo ta paidia tou kai tou moiraze aploxera info apo to inet alla kai 
genikotera tou epetrepe na ekane share kai olou ton allon pliroforion pou 
tha diakiniotane sto lan?

Hackeria in other words??!!

>> 2) Sto Cleint Ip Pool Starting Address giati xekinate oloi vazontas
>> 192.168.1.x kai oxi kapoia alla tyxeia noumera. Starting address
>> legetai giati auto pairnetai os vasi gia na
>> arxisei kai na synexistei i onomatodosia ton ip address?
> 
> Yparxoun merikes IP oi opoies legontai reserved kai xrhshmopoiountai
> gia internal dyktia ta opoia den einai routable apek'sw. To C class
> network (des http://www.webopedia.com/TERM/C/Class_C_network.html)
> 192.168.1.0 einai ena apo ta poio xarakthristika pou xrhshmopoiountai
> gia tetoious logous (yparxoun kai alla bebaia).

Nai, tora katalava, den ixera tin yparxei teoion reserved non-inet-routable 
ip addresses.

> 8a mporouses na baleis esy sto eswteriko sou dyktio opoio "starting
> address" 8eleis, alla einai pi8anon na exeis problhma. Px mporeis na
> baleis to 194.63.247.0, alla kapoio mhxanhma sto eswteriko sou dyktio
> einai pi8ano na parei apo ton router (apo to DHCP daemon basika) thn
> 194.63.247.208 (www.in.gr). Auto katalabaineis thn problhma dhmiourgei
> profanws sto eswteriko sou dyktio -> den mporeis na bgeis pros to
> dyktio 194.63.247.0 (to opoio einai kapou sto real internet) .. kai
> gia na sto poio praktika, kapoios sto eswteriko sou dyktio 8a
> prospa8hsei na anoiksei thn selida tou www.in.gr kai 8a epikoinwnhsei
> telika me kapoio allo mhxanhma sto eswteriko sou diktuo. 

Nai, sosta. Alla auto tha itan genikos mikro to kako apo tin apopsi oti 
mono to sygekrimeno real host den tha mporouse na dei o typos emsa po to 
lan, ta alla ok! 

Alla kai tora pou to skeftomai tha mporousame na to ekmetaleutoume deonots 
auto apo tin apopsi oti tha mporousame na to kanoume epitides gia ena 
gnosto host/gnosti selida px opos tou web mail provider tou. Tha nomize 
autos oti dinei to login info tou sto px mail.in.gr eno stin ousia emeis 
tha eixame setarei ena all pc sto lan na apantaei fake se auto request kai 
na loggarei ta data tou!

Kalo e? :") hackerioula again....

>> 3) Akoma den katalava ti paizei me to NAT, se ti akrivos xreiazetai
>> akthos kai gia to Port Forwarding.....
> 
> NAT -> http://www.webopedia.com/TERM/N/NAT.html kai sigoura polla alla
> resources sto dyktio gia na katalabeis ti einai auto. Praktika auto
> shmainei gia sena: Exeis ena local dyktio (pisw to apo to adsl
> routeraki sou gia paradeigma) me IPs apo to 192.168.1.0/24. To adsl
> routeraki sou otan syndeetai sto dyktio apokta mia IP (h opoia einai
> pragmatiki) kai einai routable pros kai apo ton kosmo (to internet).
> Auto pou kanei twra to NAT einai oti ka8e paketo pou er8ei apo kapoio
> host apo to eswteriko sou kai 8elei na bgei pros ta eksw, "allazei"
> ligo kai bgainei pros ta eksw me thn IP tou router/adsl (opote einai
> valid gia na ginei route). To routeraki "8ymatai" poianou host apo to
> eswteriko dyktio htan to paketo pou molis ekane forward ston eksw
> kosmo kai otan er8ei h apanthsh apo ton eksw kosmo (px h html selida
> pou zhthses [xarhn aplwthtas twra]) tote to paketo auto ginetai 
> forwared sto host tou eswterikou sou dyktiou. Auto legetai kai SNAT
> (Source NAT). To port forwarding einai na exeis thn dynatotha na
> kaneis mapping kai na les kati sto styl "otan erxetai ena paketo apo
> ton eksw kosmo sthn IP tou adsl/router kai se kapoio port tote auto to
> paketo na ginetai forwarded sto host x kai port y tou eswterikou sou
> diktiou. Auto praktika shmanei pws mporeis na exeis ena host sto
> eswteriko sou diktio pou na trexei enan apache kai na einai "visible"
> pros ton eksw kosmo (kati pou den 8a htan efikto an den eixes NAT &
> Port forwarding). 

Kali fasi!

Stin ousia to NAT "KRYVEI" tin yparxi OLON ton hosts tou esoterikou mas 
lan, eno to lan mas zei kai vasileuei! Kai oxi mono auto alla einai able na 
pairnei/dinei dedomena meso tou adsl modem/router pou tora ginetai kai 
proxy tautoxrona!!

Eipes oti to paketa apo to internal host prin vgei exo allaxei ligaki.

Allazei = Sto header information pou exei to packet itself, o routerakos 
metapoiei to source ip address apo auto tou host proeleusis tou paketou 
stin diki tou ip address?!? 

Kai ektos etsi einai kai valid e? Logo tou oti an den to ekane auto to 
192.168.0.x tha itan non valid ip address gia na steilei/parei to paketo 
afou den einai routable, auto diladi pou legame sto 1?!?

Ara kai Valid + Hidden o internal host mas! Mpraaaavo!

Xmmm, to routeraki omos pos thymatai tin origin tou paketou gia na tou 
steilei to response? Krataei kapoio internal database gia na kanei tis 
antistoixiseis?

To NAT diladi einai ena pragma san bridging metaxy internal LAN kai 
INTERNET. Voithaei kyrios ta exerxomena paketa deixnontas tous to dromo na 
vgoun pros to net kathos kai na gyrisoun eno to port forwarding apo tin 
alli mas voithaei poly emas me ta eiserxomena ston rouer paketa etsi oste 
na ta deixeiristouem opso goustaroume stelnontas sto diaolo an einai "bad" 
i ekei pou stisame tin en logo ypiresia ie web server!

Nomizo ta katalava ola auta pou eipes, an kapou esfala diorthose me!

>> Sorry again pou oi erotisiseis den einai linux oriented alla tha
>> prepei kapoia stigmi na ta ksekathariso auta.....
> 
> Yparxoun pantws polla resources & howtos pou mporeis na diabazeis gia
> ta pramata pou rwtas se poly kalyterh diatypwmenh morfh apo'ti sta lew
> egw (allwste egw sou apantaw praktika) kai se non-formal yfos.

Mia xara ta les Slaviko! :-) Panta mou aresei na mathaino kati "praktika" 
gia na ksero pos sto kalo tha mou fanei xrisimo kathos kai ta vlepo se 
friendly non-formal manner!

Na sai kala!