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syl22_00
n00b
Joined: 31 Aug 2011
Posts: 14
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 Posted: Thu Feb 21, 2013 10:14 am Post subject: Keep network access on device after it is attached to bridge |
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Hi,
I am creating a bridge to be used as device for a XEN guest. My physical device is eth0 and the bridge is xenbr0. After I start xenbr0 I lose connectivity on eth0. Meanwhile, the guest can access the network.
Here is /etc/conf.d/net:
| Code: |
config_eth0="192.168.1.61 netmask 255.255.255.0 brd 192.168.1.255"
routes_eth0="default via 192.168.1.1"
dns_servers_eth0="192.168.1.14"
bridge_xenbr0="eth0"
config_xenbr0="dhcp"
routes_xenbr0="default via 192.168.1.1"
brctl_xenbr0="setfd 0
sethello 10
stp off"
rc_net_xenbr0_need="net.eth0"
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I am quite confused whether I should turn on or off ip forwarding, in /proc/sys/net/ipv4/ip_forward or in /etc/sysctl.conf, and whether I should add entries to iptables. Any help would be very appreciated. |
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AngelKnight
Tux's lil' helper
Joined: 14 Jan 2003
Posts: 127
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| Posted: Sun Feb 24, 2013 11:07 am Post subject: |
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Hi,
This config exhibits conceptual errors with regard to what ethernet bridges in Linux are and how they work. Try this:
| Code: | config_eth0="null"
bridge_xenbr0="eth0"
config_xenbr0="dhcp
192.168.1.61/24"
routes_xenbr0="default via 192.168.1.1"
brctl_xenbr0="setfd 0
sethello 10
stp off"
dns_servers_xenbr0="192.168.1.14" # This might bomb out if you require the DNS server provided by DHCP
rc_net_xenbr0_need="net.eth0" |
The conceptual error is in thinking that an IP address belongs to a specific adapter. It doesn't; it belongs to the host. An IP was traditionally "bound" to a specific adapter in order to let the kernel know where the L3 network to which that address belongs belongs. (The previous sentence really does make sense; read it again.) |
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