[Bridge] Problem configuring bridge as a hub between host server and running VM guest

[Bridge] Problem configuring bridge as a hub between host server and running VM guest

[Ravi Varun Nair]

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Hi,
I am having a problem with configuring the bridge to work as a hub. My 
setup is the following:

 I have a RHEL host server on which I am running KVM. I have a Linux guest 
that I am running on this. A physical interface of the host is on the same 
bridge as the guest's interface. The bridge inherits the mac address of 
the physical interface on running the steps as mentioned in this link 
http://wiki.libvirt.org/page/Networking#Fedora.2FRHEL_Bridging . Also the 
static IP address that was being originally provided to the physical 
interface, is now given to the  bridge to enable networking for the host.

What I am trying to do is have a copy of all the traffic coming in on the 
physical interface be given to the VM. To configure the bridge as a hub, I 
set the ageing time value on the bridge to 0 as mentioned in a previous 
post on this list (
http://www.mail-archive.com/bridge@lists.linux-foundation.org/msg01940.html
). The problem I am facing is that on the VM,  I only see the 
traffic(using tcpdump) leaving the physical interface. I do not see the 
traffic that is coming in to the physical interface. The bridge assumes(I 
am guessing as it inherits the mac address of the physical interface), 
that the incoming traffic is meant for itself and hence does not forward 
on the traffic. 

In case a second guest is introduced in the above scenario(with an 
interface on the same bridge), then with the above configuration for 
ageing time, all the traffic going to one guest is seen by the second 
guest. So, the bridge does work as a hub for all other scenarios.

Could someone suggest if there is a way to work around this problem?

Thanks
varun

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Re: [Bridge] Problem configuring bridge as a hub between host server and running VM guest

[Stephen Hemminger]

On Fri, 4 Feb 2011 11:17:29 -0500
Ravi Varun Nair <rvnair@us.ibm.com> wrote:

> What I am trying to do is have a copy of all the traffic coming in on the 
> physical interface be given to the VM. T

A better way is to use tc mirred action to mirror packets to a dummy or other
interface.

-- 

Re: [Bridge] Problem configuring bridge as a hub between host server and running VM guest

[Andrew Woods]

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Hi,

I'm wanting to do something similar (mirror certain frames on a physical
interface to a tap device). I've never use tc before, but it seems it only
works on the L3 packet level, does it also work with all L2 frames (eg STP),
or will I need to use something like ebtables?

Thanks,
Drew

On Tue, Feb 15, 2011 at 6:03 PM, Stephen Hemminger <
shemminger@linux-foundation.org> wrote:

> On Fri, 4 Feb 2011 11:17:29 -0500
> Ravi Varun Nair <rvnair@us.ibm.com> wrote:
>
> > What I am trying to do is have a copy of all the traffic coming in on the
> > physical interface be given to the VM. T
>
> A better way is to use tc mirred action to mirror packets to a dummy or
> other
> interface.
>
> --
> _______________________________________________
> Bridge mailing list
> Bridge@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/bridge
>

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Re: [Bridge] Problem configuring bridge as a hub between host server and running VM guest

[Ravi Varun Nair]

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Thanks a ton Stephen. The tc mirred action worked well for mirroring the 
ip traffic from the host to the vm.



From:   Stephen Hemminger <shemminger@linux-foundation.org>
To:     Ravi Varun Nair/Marlborough/IBM@IBMUS
Cc:     bridge@lists.linux-foundation.org
Date:   02/15/2011 11:04 AM
Subject:        Re: [Bridge] Problem configuring bridge as a hub between 
host server and running VM guest



On Fri, 4 Feb 2011 11:17:29 -0500
Ravi Varun Nair <rvnair@us.ibm.com> wrote:

> What I am trying to do is have a copy of all the traffic coming in on 
the 
> physical interface be given to the VM. T

A better way is to use tc mirred action to mirror packets to a dummy or 
other
interface.

-- 


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