Åëëçíéêü Bridging mini-Howto
Christopher Cole cole@coledd.com
v1.11, 7 Óåðôåìâñßïõ 1998
Ôï Ýããñáöï áõôü ðåñéãñÜöåé ðùò íá óôÞóåôå ìéá ethernet ãÝöõñá. Ôé
åßíáé ìéá ethernet ãÝöõñá; Åßíáé ìéá óõóêåõÞ ðïõ åëÝã÷åé ôá ðáêÝôá
äåäïìÝíùí ìÝóá óå Ýíá õðïäßêôõï ðñïóðáèþíôáò íá ìåéþóåé ôçí
êõêëïöïñßá. Ç ãÝöõñá åßíáé óõíÞèùò ìåôáîý äýï îå÷ùñéóôþí ïìÜäùí
õðïëïãéóôþí, ðïõ åíþ ìéëïýí ðïëý ìåôáîý ôïõò, óðáíßùò ìéëÜ ç ìéá ïìÜäá
ìå ôçí Üëëç. ¸íá êáëü ðáñÜäåéãìá åßíáé áí óêåöôïýìå ìéá ïìÜäá ìå Mac-
intosh êáé ìéá ïìÜäá ìå Unix ìç÷áíÞìáôá. Êáé ïé äýï ïìÜäåò Ý÷ïõí
áõîçìÝíç êßíçóç åíôüò ôïõò, ïðüôå ç êßíçóç áõôÞ äçìéïõñãåß óõãêñïýóåéò
ìå ôçí êßíçóç ôçò Üëëçò ïìÜäáò. Ç ãÝöõñá ôïðïèåôåßôå ìåôáîý ôùí äýï
ïìÜäùí. Ç äïõëåéÜ ôçò åßíáé íá åëÝã÷åé ôá äåäïìÝíá ðïõ áíôáëëÜóóïíôáé
êáé íá áðïöáóßóåé áí ÷ñåéÜæåôáé íá ðåñÜóïõí óôçí Üëëç ðëåõñÜ ôçò
ãÝöõñáò. Ôï áðïôÝëåóìá åßíáé Ýíá ãñçãïñüôåñï êáé ðéï éó÷õñü äßêôõï ìå
ëéãüôåñåò óõãêñïýóåéò. --- Ãéá ïðïéáäÞðïôå ó÷üëéá, äéïñèþóåéò, êëð
ó÷åôéêÜ ìå ôçí åëëçíéêÞ ìåôÜöñáóç åðéêïéíùíÞóôå ìå ôïí Ðáíáãéþôç
Âïõäïýñç óôç äéåýèõíóç: panos@veria1.freeserve.co.uk
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Table of Contents
1. Setup
2. Óõ÷íÜ ðñïâëÞìáôá
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[1m1. Setup[0m
1. Âñåßôå ôï ``Bridge Config'':
<ftp://shadow.cabi.net/pub/Linux/BRCFG.tgz>
2. ÅíåñãïðïéÞóôå ðïëëáðëÝò ethernet óõóêåõÝò âÜæïíôáò ôï ðáñáêÜôù óôï
/etc/lilo.conf, êáé îáíÜ-ôñÝ÷ïíôáò ôï lilo:
append = "ether=0,0,eth1"
Áí Ý÷åôå ôñåéò óõóêåõÝò óôç ãÝöõñá âÜëôå ôï ðáñáêÜôù áíôß ôùí Üíù:
append = "ether=0,0,eth1 ether=0,0,eth2"
Ðåñéóóüôåñåò óõóêåõÝò ìðïñïýí íá ðñïóôåèïýí ìå ðåñéóóüôåñåò äçëþóåéò
ether. ¸íáò Ýôïéìïò ðõñÞíáò øÜ÷íåé ãéá ìßá êÜñôá êáé ìüëéò ôç âñåé
óôáìáôÜ ôï øÜîéìï. Ìå ôçí ðáñáðÜíù åíôïëÞ óõíå÷ßæåé íá øÜ÷íåé êáé ìåôÜ
ôçí ðñþôç êÜñôá.
Áíôß ôùí Üíù, ìðïñåßôå íá ÷ñçóéìïðïéÞóåôå ôçí ðáñáêÜôù ðáñÜìåôñï
åêêßíçóçò:
linux ether=0,0,eth1
¹ ìå 3 óõóêåõÝò:
linux ether=0,0,eth1 ether=0,0,eth2
3. Áíáìåôáëùôôßóôå ôïí ðõñÞíá ìå ôï BRIDGING åíåñãïðïéçìÝíï.
4. Ç ãÝöõñá äå èá ðñÝðåé íá Ý÷åé IP äéåýèõíóç. ÌÐÏÑÅÉ íá Ý÷åé áëëÜ ìéá
áðëÞ ãÝöõñá äåí ôçí ÷ñåéÜæåôáé. Ãéá íá áöáéñÝóåôå ôçí IP äéåýèõíóç
áðü ôç ãÝöõñÜ óáò, ðçãáßíåôå óôï /etc/sysconfig/network-
scripts/ (ãéá RedHat óýóôçìá) êáé áíôéãñÜøôå ôï ifcfg-lo0 óå ifcfg-
eth0 & ifcfg-eth1. Óôá äýï áõôÜ áñ÷åßá áëëÜîôå ôç ãñáììÞ ðïõ
ðåñéÝ÷åé ôï ``DEVICE=lo'' óå ``DEVICE=eth0'' êáé ``DEVICE=eth1''.
¶ëëåò äéáíïìÝò ìðïñåß íá äéáöÝñïõí, êÜíôå ü,ôé ÷ñåéÜæåôáé! Áí Ý÷åôå
ðÜíù áðü äýï óõóêåõÝò óôç ãÝöõñá óéãïõñåõôåßôå íá äéïñèþóåôå üëåò
ôéò ñõèìßóåéò.
5. Åðáíåêêßíçóç, þóôå íá Ý÷åôå ôïí íÝï ðõñÞíá êáé îáíáóéãïõñåõôåßôå
üôé ç ãÝöõñá äåí Ý÷åé IP äéåõèýíóåéò.
6. Ìüëéò ôï óýóôçìá îåêéíÞóåé, âÜëôå ôéò ethernet êÜñôåò óå
promiscuous mode, þóôå íá åëÝã÷ïõí ïôéäÞðïôå ðåñíÜåé áðü áõôÝò:
ifconfig eth0 promisc ; ifconfig eth1 promisc
¼ëåò ïé êÜñôåò ðïõ åßíáé íá óõíäåèïýí óå ãÝöõñá ðñÝðåé íá ìðïõí óå
promiscuous mode.
7. ÅíåñãïðïéÞóôå ôï bridging ÷ñçóéìïðïéþíôáò ôï ðñüãñáììá brcfg:
brcfg -ena
8. Âåâáéùèåßôå üôé õðÜñ÷åé äéáöïñåôéêÞ êßíçóç óå êÜèå ôìÞìá:
tcpdump -i eth0 (in one window)
tcpdump -i eth1 (in another window)
9. ÔñÝîôå Ýíá sniffer Þ ôï tcpdump óå Üëëï ìç÷Üíçìá ãéá íá äåßôå üôé ç
ãÝöõñá áðïêüðôåé ôá ôìÞìáôá êáíïíéêÜ.
[1m2. Óõ÷íÜ ðñïâëÞìáôá[0m
1.
[1mQuestion[0m
Ðáßñíù ôï ìÞíõìá
ioctl(SIOCGIFBR) failed: Package not installed
Ôé óçìáßíåé;
[1mAnswer[0m
Äåí Ý÷åôå bridging äõíáôüôçôåò óôïí ðõñÞíá. ÐÜñôå ðõñÞíá 2.0 Þ
ìåãáëýôåñï, êáé áíáìåôáãëùôôßóôå ôï ìå ôçí åðéëïãÞ BRIDGING
åíåñãïðïéçìÝíç.
2.
[1mQuestion[0m
Ìç÷áíÞìáôá óôç ìßá ðëåõñÜ äå ìðïñïýí íá êÜíïõí ping óôçí Üëëç!
[1mAnswer[0m
· ÅíåñãïðïéÞóáôå ôï bridging ìå ``brcfg -ena''; (ôï brcfg èá
ðñÝðåé íá ëÝåé ``bridging is ENABLED'')
· ÂÜëáôå ôéò êÜñôåò óå promiscuous mode? (ãñÜøôå ``ifconfig''.
Ôï ``PROMISC'' ðñÝðåé íá åìöáíéóôåß êáé óôéò äýï ðëåõñÝò.)
· Áí ÷ñçóéìïðïéåßôå êÜñôåò äéáóýíäåóçò ðïëëáðëþí ìÝóùí
óéãïõñåõôåßôå üôé ôï óùóôü Ý÷åé åíåñãïðïéçèåß. ºóùò ÷ñåéáóôåß íá
÷ñçóéìïðïéÞóåôå ôï ðñüãñáììá ñõèìßóåùí ðïõ ðÞñáôå ìå ôçí êÜñôá.
3.
[1mQuestion[0m
Äå ìðïñþ íá êÜíù telnet/ftp áðü ôç ãÝöõñá! Ãéáôß;
[1mAnswer[0m
Áõôü äå ãßíåôáé åöüóïí äåí õðÜñ÷åé IP äéåýèõíóç óôç ãÝöõñá. Ç
ãÝöõñá ðñÝðåé íá åßíáé Ýíá äéÜöáíï ìÝñïò ôïõ äéêôýïõ.
4.
[1mQuestion[0m
Ôé ðñÝðåé íá êÜíù ãéá íá ñõèìßóù ôç äñïìïëüãçóç;
[1mAnswer[0m
Ôßðïôá! Ç äñïìïëüãçóç åëÝã÷åôáé áðü ôïí êþäéêá ôïõ ðõñÞíá. Ãéá
íá äåßôå ôéò ethernet äéåõèýíóåéò üðùò ìáèáßíïíôáé áðü ôç ãÝöõñá
÷ñçóéìïðïéÞóôå ôï brcfg óå debug mode:
brcfg -deb
5.
[1mQuestion[0m
Ç ãÝöõñá öáßíåôáé íá äïõëåýåé, áëëÜ ôï ``traceroute'' äå äåß÷íåé
ôç ãÝöõñá ùò ìÝñïò ôçò äéáäñïìÞò.
[1mAnswer[0m
Ëüãù ôçò öýóçò ôçò ãÝöõñáò, ôï ``traceroute'' ÄÅÍ ðñÝðåé íá
äåßîåé ôç ãÝöõñá. Ç ãÝöõñá åßíáé äéáöáíÞò óôï äßêôõï.
6.
[1mQuestion[0m
Åßíáé áðáñáßôçôï íá ìåôáãëùôôßóù ôïí ðõñÞíá ìå IP_FORWARD;
[1mAnswer[0m
¼÷é. Ï êþäéêáò ãéá ôï bridging óôïí ðõñÞíá öñïíôßæåé ãéá ôç
ìåôáöïñÜ. Ôï IP_FORWARD åßíáé ãéá ðýëç ðïõ Ý÷åé IP äéåýèõíóç.
7.
[1mQuestion[0m
Ãéáôß ïé äéåõèýíóåéò ãéá ôç èýñá 1 êáé èýñá 2 åßíáé ßäéåò
óýìöùíá ìå ôï ``brcfg''; Äå èá Ýðñåðå íá åßíáé äéáöïñåôéêÝò;
[1mAnswer[0m
¼÷é. ÊÜèå èýñá óôç ãÝöõñá Ý÷åé åðßôçäåò ôçí ßäéá äéåýèõíóç, üðùò
äßíåôáé áðü ôïí êþäéêá ôïõ bridging.
8.
[1mQuestion[0m
Ôï bridging äåí åìöáíßæåôáé ùò åðéëïãÞ üôáí êÜíù make config ãéá
ôïí ðõñÞíá. Ðùò ôï åíåñãïðïéþ;
[1mAnswer[0m
ÊáôÜ ôçí ðáñáìåôñïðïßçóç, áðáíôÞóôå 'Y' óôçí åñþôçóç: ``Prompt
for development and/or incomplete code/drivers
(CONFIG_EXPERIMENTAL) [Y/n/?]''.
9.
[1mQuestion[0m
Ðïëëïß êüìâïé (hubs, 4 Þ ðáñáðÜíù) óõíäåìÝíá óå óåéñÜ ðñïêáëïýí
ðñïâëÞìáôá óõã÷ñïíéóìïý óå ethernet. Ôé åðéðôþóåéò Ý÷åé áõôü óå
Ýíá õðïäßêôõï ðïõ åßíáé óôçìÝíï ìå hubs;
[1mAnswer[0m
Ç ãÝöõñá áíáïñßæåé ôïí êáíüíá ôùí 3/4/5 êüìâùí. Ç ãÝöõñá äåí
÷åéñßæåôáé ôá ðáêÝôá äåäïìÝíùí üðùò Ýíá hub, ïðüôå äåí
äçìéïõñãåß ðñïâëÞìáôá óõã÷ñïíéóìïý óôï äßêôõï.
10.
[1mQuestion[0m
Ìðïñåß ìéá ãÝöõñá íá óõíäÝóåé äýï ôìÞìáôá ìå 10Mb êáé 100Mb;
ÔÝôïéá äéáìüñöùóç èá åðçñåÜóåé ôçí ôá÷ýôçôá óôçí ãñÞãïñá ðëåõñÜ;
[1mAnswer[0m
Íáé, ç ãÝöõñá ìðïñåß íá óõíäÝóåé Ýíá ôìÞìá 10Mb ìå Ýíá ôìÞìá
100Mb. Åöüóïí ç êÜñôá äéêôýïõ óôï ãñÞãïñï äßêôõï öôÜíåé ôá
100Mb, ôï TCP öñïíôßæåé ãéá ôá õðüëïéðá. ÖõóéêÜ, ôá äåäïìÝíá áðü
ôï ãñÞãïñï ðñïò ôï áñãü ôìÞìá èá ìåôáöÝñïíôáé ìå 10Mb/s, áëëÜ ç
õðüëïéðç êßíçóç óôï ãñÞãïñï äßêôõï äåí åðéâñáäýíåôáé.
