Acabei de instalar o Ubuntu 12.10 em cerca de 30 computadores em um laboratório de informática do ensino médio (e excluí o Win XP e o Win 7). O problema que tenho agora é que não podemos acessar a internet pela nossa rede.
A escola tem um roteador aDSL e um único cabo ethernet que chega ao laboratório de informática. Este cabo se conecta a um switch Ethernet Trendnet de 24 portas. Metade dos computadores estão conectados a esse switch. Outro cabo ethernet vai deste switch para um switch idêntico em todo o laboratório, dando acesso à internet para a outra metade dos computadores. Eu não configurei a rede dessa maneira, mas costumava funcionar quando os computadores tinham janelas carregadas neles. Depois de instalar o Ubuntu, não temos mais conectividade com a Internet pela rede.
Quando eu conecto o cabo ethernet do roteador aDSL diretamente a um dos computadores, a internet funciona corretamente, mas quando eu conecto ao switch nós não obtemos nada. O Ubuntu nem atribui endereços IP locais ao computador quando configurado para DHCP automático. Eu tentei definir endereços IP manuais fora do intervalo de DHCP: eu definir o endereço ip para 192.168.1.101 a 192.168.1.130. Eu configurei o gateway para 192.168.1.1, a máscara de sub-rede para 255.255.255.0 e o roteador DNS para 192.168.1.1. Mais tarde eu mudei o roteador DNS para os endereços IP do Openend.
Configurar os endereços IP manualmente permitiu que eu fizesse ping em computadores na rede local, desde que estivessem no mesmo switch. O tempo limite se o computador estivesse no outro switch ou se eles estivessem fora da rede local e ainda não tivessem acesso à Internet.
Eu também tentei reiniciar o roteador e os switches sem sorte.
Alguém tem alguma sugestão sobre como acessar a internet em nossa rede local e como conectar os computadores em ambas as centrais?
EDITAR:
Aqui está o que o syslog me oferece:
computer8 dbus[835]: [system] Successfully activated service 'org.freedesktop.PolicyKit1'
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: init!
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: update_system_hostname
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPluginIfupdown: management mode: unmanaged
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: devices added (path: /sys/devices/pci0000:00/0000:00:05.0/0000:02:00.0/net/eth0, iface: eth0)
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: device added (path: /sys/devices/pci0000:00/0000:00:05.0/0000:02:00.0/net/eth0, iface: eth0): no ifupdown configuration found.
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/lo, iface: lo)
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/lo, iface: lo): no ifupdown configuration found.
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: end _init.
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> Loaded plugin ifupdown: (C) 2008 Canonical Ltd. To report bugs please use the NetworkManager mailing list.
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> Loaded plugin keyfile: (c) 2007 - 2010 Red Hat, Inc. To report bugs please use the NetworkManager mailing list.
Feb 19 16:18:59 computer8 NetworkManager[902]: Ifupdown: get unmanaged devices count: 0
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: (-1240455032) ... get_connections.
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: (-1240455032) ... get_connections (managed=false): return empty list.
Feb 19 16:18:59 computer8 NetworkManager[902]: keyfile: parsing Wired connection 1 ...
Feb 19 16:18:59 computer8 NetworkManager[902]: keyfile: read connection 'Wired connection 1'
Feb 19 16:18:59 computer8 NetworkManager[902]: Ifupdown: get unmanaged devices count: 0
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> modem-manager is now available
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> monitoring kernel firmware directory '/lib/firmware'.
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> WiFi enabled by radio killswitch; enabled by state file
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> WWAN enabled by radio killswitch; enabled by state file
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> WiMAX enabled by radio killswitch; enabled by state file
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> Networking is enabled by state file
Feb 19 16:18:59 computer8 NetworkManager[902]: <warn> failed to allocate link cache: (-10) Operation not supported
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): carrier is OFF
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): new Ethernet device (driver: 'r8169' ifindex: 2)
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): exported as /org/freedesktop/NetworkManager/Devices/0
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): now managed
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2]
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): bringing up device.
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): preparing device.
Feb 19 16:18:59 computer8 NetworkManager[902]: <info> (eth0): deactivating device (reason 'managed') [2]
Feb 19 16:18:59 computer8 NetworkManager[902]: <warn> /sys/devices/virtual/net/lo: couldn't determine device driver; ignoring...
Feb 19 16:18:59 computer8 NetworkManager[902]: <warn> /sys/devices/virtual/net/lo: couldn't determine device driver; ignoring...
Feb 19 16:18:59 computer8 kernel: [ 15.621206] r8169 0000:02:00.0: >eth0: link down
Feb 19 16:18:59 computer8 kernel: [ 15.621396] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
Feb 19 16:18:59 computer8 kernel: [ 15.621674] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
Feb 19 16:18:59 computer8 avahi-daemon[905]: Network interface enumeration completed.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Registering HINFO record with values 'I686'/'LINUX'.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Server startup complete. Host name is computer8.local. Local service cookie is 2464504904.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Service "computer8" (/services/udisks.service) successfully established.
Feb 19 16:18:59 computer8 anacron[996]: Anacron 2.3 started on 2013-02-19
Feb 19 16:18:59 computer8 acpid: starting up with proc fs
Feb 19 16:18:59 computer8 cron[966]: (CRON) INFO (pidfile fd = 3)
Feb 19 16:18:59 computer8 kernel: [ 15.777742] Bridge firewalling registered
Feb 19 16:18:59 computer8 avahi-daemon[905]: Joining mDNS multicast group on interface lxcbr0.IPv4 with address 10.0.3.1.
Feb 19 16:18:59 computer8 avahi-daemon[905]: New relevant interface lxcbr0.IPv4 for mDNS.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Registering new address record for 10.0.3.1 on lxcbr0.IPv4.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Withdrawing address record for 10.0.3.1 on lxcbr0.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Leaving mDNS multicast group on interface lxcbr0.IPv4 with address 10.0.3.1.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Interface lxcbr0.IPv4 no longer relevant for mDNS.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Joining mDNS multicast group on interface lxcbr0.IPv4 with address 10.0.3.1.
Feb 19 16:18:59 computer8 avahi-daemon[905]: New relevant interface lxcbr0.IPv4 for mDNS.
Feb 19 16:18:59 computer8 avahi-daemon[905]: Registering new address record for 10.0.3.1 on lxcbr0.IPv4.
Feb 19 16:18:59 computer8 NetworkManager[902]: <warn> /sys/devices/virtual/net/lxcbr0: couldn't determine device driver; ignoring...
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/lxcbr0, iface: lxcbr0)
Feb 19 16:18:59 computer8 NetworkManager[902]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/lxcbr0, iface: lxcbr0): no ifupdown configuration found.
Feb 19 16:19:00 computer8 cron[1048]: (CRON) STARTUP (fork ok)
Feb 19 16:19:00 computer8 cron[1048]: (CRON) INFO (Running @reboot jobs)
Feb 19 16:19:00 computer8 ntpdate[1051]: Can't find host ntp.ubuntu.com: Name or service not known (-2)
Feb 19 16:19:00 computer8 ntpdate[1051]: no servers can be used, exiting
Feb 19 16:19:00 computer8 kernel: [ 15.855197] ip_tables: (C) 2000-2006 Netfilter Core Team
Feb 19 16:19:00 computer8 kernel: [ 15.865021] nf_conntrack version 0.5.0 (11983 buckets, 47932 max)
Feb 19 16:19:00 computer8 dnsmasq[1073]: started, version 2.63rc6 cachesize 150
Feb 19 16:19:00 computer8 dnsmasq[1073]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack
Feb 19 16:19:00 computer8 dnsmasq-dhcp[1073]: DHCP, IP range 10.0.3.2 -- 10.0.3.254, lease time 1h
Feb 19 16:19:00 computer8 dnsmasq[1073]: no servers found in /etc/resolv.conf, will retry
Feb 19 16:19:00 computer8 dnsmasq[1073]: read /etc/hosts - 7 addresses
Feb 19 16:19:00 computer8 anacron[996]: Will run job 'cron.daily' in 5 min.
Feb 19 16:19:00 computer8 anacron[996]: Jobs will be executed sequentially
Feb 19 16:19:00 computer8 dbus[835]: [system] Activating service name='org.freedesktop.Accounts' (using servicehelper)
Feb 19 16:19:00 computer8 accounts-daemon[1094]: started daemon version 0.6.21
Feb 19 16:19:00 computer8 dbus[835]: [system] Successfully activated service 'org.freedesktop.Accounts'
Feb 19 16:19:00 computer8 dbus[835]: [system] Activating service name='org.freedesktop.ConsoleKit' (using servicehelper)
Feb 19 16:19:00 computer8 dbus[835]: [system] Successfully activated service 'org.freedesktop.ConsoleKit'
Feb 19 16:19:01 computer8 kernel: [ 17.130284] r8169 0000:02:00.0: >eth0: link up
Feb 19 16:19:01 computer8 kernel: [ 17.130497] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> (eth0): carrier now ON (device state 20)
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> (eth0): device state change: unavailable -> disconnected (reason 'carrier-changed') [20 30 40]
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Auto-activating connection 'Wired connection 1'.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) starting connection 'Wired connection 1'
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> (eth0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) scheduled...
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) started...
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) scheduled...
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) complete.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) starting...
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> (eth0): device state change: prepare -> config (reason 'none') [40 50 0]
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) successful.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) scheduled.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) complete.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) started...
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> (eth0): device state change: config -> ip-config (reason 'none') [50 70 0]
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Configure Commit) scheduled...
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Beginning IP6 addrconf.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
Feb 19 16:19:01 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) started...
Feb 19 16:19:01 computer8 avahi-daemon[905]: Joining mDNS multicast group on interface eth0.IPv4 with address 192.168.1.108.
Feb 19 16:19:01 computer8 avahi-daemon[905]: New relevant interface eth0.IPv4 for mDNS.
Feb 19 16:19:01 computer8 avahi-daemon[905]: Registering new address record for 192.168.1.108 on eth0.IPv4.
Feb 19 16:19:01 computer8 acpid: 33 rules loaded
Feb 19 16:19:01 computer8 acpid: waiting for events: event logging is off
Feb 19 16:19:01 computer8 acpid: client connected from 1067[0:0]
Feb 19 16:19:01 computer8 acpid: 1 client rule loaded
Feb 19 16:19:01 computer8 avahi-daemon[905]: Joining mDNS multicast group on interface lxcbr0.IPv6 with address fe80::ac67:41ff:fe66:c671.
Feb 19 16:19:01 computer8 avahi-daemon[905]: New relevant interface lxcbr0.IPv6 for mDNS.
Feb 19 16:19:01 computer8 avahi-daemon[905]: Registering new address record for fe80::ac67:41ff:fe66:c671 on lxcbr0.*.
Feb 19 16:19:01 computer8 dbus[835]: [system] Activating service name='org.freedesktop.UPower' (using servicehelper)
Feb 19 16:19:01 computer8 dbus[835]: [system] Successfully activated service 'org.freedesktop.UPower'
Feb 19 16:19:02 computer8 avahi-daemon[905]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::224:21ff:fea0:cfd0.
Feb 19 16:19:02 computer8 avahi-daemon[905]: New relevant interface eth0.IPv6 for mDNS.
Feb 19 16:19:02 computer8 avahi-daemon[905]: Registering new address record for fe80::224:21ff:fea0:cfd0 on eth0.*.
Feb 19 16:19:02 computer8 kernel: [ 17.856246] IPv6: eth0: IPv6 duplicate address fe80::224:21ff:fea0:cfd0 detected!
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> (eth0): device state change: ip-config -> activated (reason 'none') [70 100 0]
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> DNS: starting dnsmasq...
Feb 19 16:19:02 computer8 NetworkManager[902]: <error> [1361251142.663612] [nm-dns-dnsmasq.c:390] update(): dnsmasq not available on the bus, can't update servers.
Feb 19 16:19:02 computer8 NetworkManager[902]: <error> [1361251142.663656] [nm-dns-dnsmasq.c:392] update(): dnsmasq owner not found on bus: Could not get owner of name 'org.freedesktop.NetworkManager.dnsmasq': no such name
Feb 19 16:19:02 computer8 NetworkManager[902]: <warn> DNS: plugin dnsmasq update failed
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> ((null)): writing resolv.conf to /sbin/resolvconf
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> Policy set 'Wired connection 1' (eth0) as default for IPv4 routing and DNS.
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> Activation (eth0) successful, device activated.
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) complete.
Feb 19 16:19:02 computer8 dbus[835]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
Feb 19 16:19:02 computer8 dbus[835]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Feb 19 16:19:02 computer8 NetworkManager[902]: <warn> dnsmasq appeared on DBus: :1.22
Feb 19 16:19:02 computer8 dnsmasq[1506]: started, version 2.63rc6 cache disabled
Feb 19 16:19:02 computer8 dnsmasq[1506]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack
Feb 19 16:19:02 computer8 dnsmasq[1506]: DBus support enabled: connected to system bus
Feb 19 16:19:02 computer8 dnsmasq[1506]: warning: no upstream servers configured
Feb 19 16:19:02 computer8 NetworkManager[902]: <info> ((null)): writing resolv.conf to /sbin/resolvconf
Feb 19 16:19:02 computer8 dnsmasq[1506]: setting upstream servers from DBus
Feb 19 16:19:02 computer8 dnsmasq[1506]: using nameserver 208.67.220.220#53
Feb 19 16:19:02 computer8 dnsmasq[1506]: using nameserver 208.67.222.222#53
Isso é o que ifconfig me dá
eth0 Link encap:Ethernet HWaddr 00:24:21:a0:cf:d0
inet addr:192.168.1.108 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::224:21ff:fea0:cfd0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1039910 errors:0 dropped:0 overruns:0 frame:0
TX packets:199 errors:0 dropped:47 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:68572248 (68.5 MB) TX bytes:16079 (16.0 KB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:176 errors:0 dropped:0 overruns:0 frame:0
TX packets:176 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:13122 (13.1 KB) TX bytes:13122 (13.1 KB)
lxcbr0 Link encap:Ethernet HWaddr ae:67:41:66:c6:71
inet addr:10.0.3.1 Bcast:10.0.3.255 Mask:255.255.255.0
inet6 addr: fe80::ac67:41ff:fe66:c671/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:40 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:7989 (7.9 KB)
Parece que os roteadores não estão configurados corretamente para encaminhar solicitações DHCP. Você poderia verificar os logs para ver se os computadores ainda enviam as solicitações corretamente? (deve estar visível no visualizador de registros - > syslog)