[ovs-discuss] why vm can't ping host eth1

[Salman Malik]

Thanks Robin and Reid. Its still a little fuzzy to me. Can you suggest some pointers which explains the bridge and related interfaces configuration ? 
I have worked for some time with ovs and integration bridge (that ovs manages) and I couldn't get my head around the routing mechanism e.g. doing an ifconfig would show all the interfaces like br100 and eth1. So is bridge an interface or an emulation of a real bridge ? (because I could see a HWaddress associated with this bridge/interface... and for some reason I think that each port of real bridge should have a MAC/IP associated with it, but I don't know). And when we add interface eth1 to br100 as a port, I understand that all the VM traffic would now go through eth1 (acting as an uplink, and conveying traffic from bridge to real switch and the VMs themselves can get the IP address in the same subnet as host itself, right?), but I can't visualize the scenario, given the output of ifconfig, brctl show or ovs-vsctl show/ ovs-ofctl show br100.

Any explanation is much appreciated.

Thanks,
Salman

CC: salmanmk at live.com; discuss at openvswitch.org
From: reid at nicira.com
Subject: Re: [ovs-discuss] why vm can't ping host eth1
Date: Thu, 17 May 2012 22:31:08 -0700
To: cloudbengo at gmail.com

One thing I have seen in the past: if ethX has an ip as well as brX, it usually means that routing will try to send traffic out ethX. That traffic will be dropped, since brX is now the one hooked up to the ip stack (not ethX).
On May 17, 2555 BE, at 20:49, Robin Wang <cloudbengo at gmail.com> wrote:

eth1, sorry for typo mistake.
在 2012-5-18 上午11:48，"Robin Wang" <cloudbengo at gmail.com>写道：

Because uplink doesn't need IP address. Here eth0 is used to connect two switches, one virtual, one physical. Thanks.
在 2012-5-18 上午10:49，"Salman Malik" <salmanmk at live.com>写道：






Hi Dongsheng,

Could you please tell me, why do we need to clear up the eth1 IP address? Does it interfere with the bridge ? If yes then how ?


Bridge management is a bit unclear to me so thats why I am asking.

Thanks,
Salman


> From: dongsheng.song at gmail.com


> Date: Fri, 18 May 2012 10:32:23 +0800
> To: heuye.wang at gmail.com
> CC: discuss at openvswitch.org


> Subject: Re: [ovs-discuss] why vm can't ping host eth1
> 
> On Thu, May 17, 2012 at 7:12 PM, yue wang <heuye.wang at gmail.com> wrote:

> >

> > i think vm1/vm2/host are connected to each other by OVS, vm and host should communicate with each other.
> 
> Sure, please see another thread:
> http://openvswitch.org/pipermail/discuss/2012-May/007201.html


> 
> You must clean ALL ip address on eth1, and set the ip address on the
> corresponding bridge device,
> say 'br1', here is a example:
> 
> /usr/bin/ovs-vsctl add-br br1
> /usr/bin/ovs-vsctl add-port br1 eth1


> 
> /sbin/ip addr add ${IP} dev br1
> /sbin/ip link set br1 up
> /sbin/ip address flush dev eth1
> /sbin/ip route replace default via ${GW} # if you have gateway
> corresponding  eth1


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