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I had successfully installed KVM in Gentoo , and set network in bridge mode as the document described (direct bridging , not NAT). Now my guest and host OS can connect each other via ping , ssh and samba , so the bridged subnet seems OK. I even tried this from another standalone Win7 machine which is in the same local network , and the successing result confirmed that my local network is fine.

But the problem comes when I try to connect to the internet. My host OS uses PPPoE (ADSL) to connect to internet , and this is not work in my guest OS. It's odd that my guest can make ( pppoeconf ) a ppp0 interface , but the browser will report "Address Not Found" . I'm sure the /etc/resolv.conf in the guest OS is valid , so the DNS setting is correct. After Googleing several hours and failed again by following a article named "Sharing PPP Connection", I still have no idea.

This is my host/guest OS :

Host : Gentoo with 2.6.39-r3
Guest : EliveOS

The bridge status :

#brctl show
bridge name bridge id         STP enable interfaces
br0         8000.000000000001 no         eth0
                                         tap0  -- guest os
                                         tap1

I've set the tap0 and eth0 in host 00.00.00.00 and set them up :

#ifconfig -a
br0   Link encap:Ethernet  HWaddr 00:00:00:00:00:01
      inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
      inet6 addr: fe80::200:ff:fe00:1/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:14866 errors:0 dropped:6 overruns:0 frame:0
      TX packets:7842 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0
      RX bytes:1976293 (1.8 MiB)  TX bytes:1553199 (1.4 MiB)

eth0  Link encap:Ethernet  HWaddr 00:23:5a:b7:ef:9d
      inet6 addr: fe80::223:5aff:feb7:ef9d/64 Scope:Link
      UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
      RX packets:14419 errors:0 dropped:0 overruns:0 frame:0
      TX packets:8313 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000
      RX bytes:2117805 (2.0 MiB)  TX bytes:1580954 (1.5 MiB)
      Interrupt:19 Base address:0x8000

ppp0  Link encap:Point-to-Point Protocol
      inet addr:111.250.45.123  P-t-P:168.95.98.254  Mask:255.255.255.255
      UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1
      RX packets:8281 errors:0 dropped:0 overruns:0 frame:0
      TX packets:7331 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:3
      RX bytes:1249010 (1.1 MiB)  TX bytes:1360943 (1.2 MiB)

tap0  Link encap:Ethernet  HWaddr 00:00:00:00:00:01
      inet6 addr: fe80::200:ff:fe00:1/64 Scope:Link
      UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
      RX packets:4323 errors:0 dropped:0 overruns:0 frame:0
      TX packets:5828 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:500
      RX bytes:537950 (525.3 KiB)  TX bytes:658979 (643.5 KiB)

And my PPPoE is using br0 interface because a connection using eth0 wouldn't work.

share|improve this question
    
What does sysctl net.ipv4.ip_forward on your host say? –  Steven Monday Aug 19 '11 at 16:36
    
Also on your host and guest: What does ip route show report? –  Steven Monday Aug 19 '11 at 16:38
    
I finally solve the problem : 1. iptables need be started 2. iptables -P FORWARD ACCEPT . Thanks all people try to give me suggestions. –  snowmantw Aug 20 '11 at 14:12
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