[Bridge] Bridging LACP (802.3ad) frames not working

[Bridge] Bridging LACP (802.3ad) frames not working

[Jean-Michel Hautbois]

Hi there !

I have connected two ethernet 1000Mbps interfaces to my routers, and I
have built a bridge between them :
eth1 <---> br0 <---> eth2

When I am transmitting UDP, ADP, ARP or any other type of frames, I
don't have any problem.
But when, the router sends LACP packets, it is not transmitted
(neither from eth1 to eth2 than from eth2 to eth1).

I can't figure out why, so if you have an idea, thanks in advance for
your help !

Best Regards !
JM

Re: [Bridge] Bridging LACP (802.3ad) frames not working

[Ross Vandegrift]

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On Tue, Jan 12, 2010 at 04:13:01PM +0100, Jean-Michel Hautbois wrote:
> Hi there !
> 
> I have connected two ethernet 1000Mbps interfaces to my routers, and I
> have built a bridge between them :
> eth1 <---> br0 <---> eth2
> 
> When I am transmitting UDP, ADP, ARP or any other type of frames, I
> don't have any problem.
> But when, the router sends LACP packets, it is not transmitted
> (neither from eth1 to eth2 than from eth2 to eth1).
> 
> I can't figure out why, so if you have an idea, thanks in advance for
> your help !

You can't bridge LACP - it doesn't even make sense.  LACP bundles must
be between adjacent devices.  Moreover,  LACPDUs are destined for a
bridge-management address that is prohibited from being bridged by
802.1D.

What are you trying to accomplish?  If you want to transparently
bridge with LACP channels, you should terminate the LACP bundles on
the Linux box and bridge the bundles:

eth0 \                          / eth2
      bond0 ----- br0 ---- bond1
eth1 /                          \ eth3

And then cable eth0/eth1 to one device and eth2/eth3 to the other.

Ross

-- 
Ross Vandegrift
ross@kallisti.us

"If the fight gets hot, the songs get hotter.  If the going gets tough,
the songs get tougher."
	--Woody Guthrie

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[Bridge] Re :Re: Bridging LACP (802.3ad) frames not working

[jhautbois]

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Hi Ross,

Le 12 janv. 2010 16:23, Ross Vandegrift <ross@kallisti.us> a écrit :
> You can't bridge LACP - it doesn't even make sense. LACP bundles must

> be between adjacent devices. Moreover, LACPDUs are destined for a

> bridge-management address that is prohibited from being bridged by

> 802.1D.


OK, I agree, it doesn't make sense, but I want to be transparent using  
bridging. I can't explain my idea :).

> What are you trying to accomplish? If you want to transparently

> bridge with LACP channels, you should terminate the LACP bundles on

> the Linux box and bridge the bundles:



> eth0 \ / eth2

> bond0 ----- br0 ---- bond1

> eth1 / \ eth3


You mean I need to have four physical interfaces ?
I can't understand how too accomplish this.
Currently, I am doing :
brctl addif eth1
brctl addif eth2

> And then cable eth0/eth1 to one device and eth2/eth3 to the other.
How ?


Thanks !
JM

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Re: [Bridge] Re :Re: Bridging LACP (802.3ad) frames not working

[Jean-Michel Hautbois]

Hi, me again...

>> eth0 \                          / eth2
>>
>>      bond0 ----- br0 ---- bond1
>>
>> eth1 /                          \ eth3
>>
>

I only have two physical ports (eth0 and eth1).
Do you think, with your solution, that I should bond eth0 with a
virtual network interface ; bonding eth1 with another virtual
interface.
Then, I have a bridge between bond0 and bond1 ?

I cannot have 4 physical interfaces.

Thanks in advance !
Regards,
JM

Re: [Bridge] Re :Re: Bridging LACP (802.3ad) frames not working

[Ross Vandegrift]

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On Tue, Jan 12, 2010 at 03:28:53PM +0000, jhautbois@gmail.com wrote:
> OK, I agree, it doesn't make sense, but I want to be transparent using  
> bridging. I can't explain my idea :).

You can't be transparent with respect to LACP if you're using ethernet
to bridge.  It doesn't make sense - LACP is negotiated between bridge
ports on a point-to-point ethernet interface.

> You mean I need to have four physical interfaces ?
> I can't understand how too accomplish this.
> Currently, I am doing :
> brctl addif eth1
> brctl addif eth2

No - you don't need four physical interfaces.  I was trying to
extrapolate what problem you might be trying to solve, and I think I
guessed wrong.  I imagined that you needed a multi-interface bundle
through a Linux bridge.

If you just want your box to speak LACP to the adjacent switches, you
could easily make bond interfaces with single ethernet interfaces.
But it sounds like you don't want to speak LACP to the switches, you
want to pass it as if you were a layer 1 device.

Ross

-- 
Ross Vandegrift
ross@kallisti.us

"If the fight gets hot, the songs get hotter.  If the going gets tough,
the songs get tougher."
	--Woody Guthrie

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[Bridge] Re :Re: Re :Re: Bridging LACP (802.3ad) frames not working

[jhautbois]

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Le , Ross Vandegrift <ross@kallisti.us> a écrit :
> On Tue, Jan 12, 2010 at 03:28:53PM +0000, jhautbois@gmail.com wrote:

> > OK, I agree, it doesn't make sense, but I want to be transparent using

> > bridging. I can't explain my idea :).



> You can't be transparent with respect to LACP if you're using ethernet

> to bridge. It doesn't make sense - LACP is negotiated between bridge

> ports on a point-to-point ethernet interface.



> > You mean I need to have four physical interfaces ?

> > I can't understand how too accomplish this.

> > Currently, I am doing :

> > brctl addif eth1

> > brctl addif eth2



> No - you don't need four physical interfaces. I was trying to

> extrapolate what problem you might be trying to solve, and I think I

> guessed wrong. I imagined that you needed a multi-interface bundle

> through a Linux bridge.



> If you just want your box to speak LACP to the adjacent switches, you

> could easily make bond interfaces with single ethernet interfaces.

> But it sounds like you don't want to speak LACP to the switches, you

> want to pass it as if you were a layer 1 device.


This is exactly the problem.
But, sounds like it is not possible... ?

JM

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Re: [Bridge] Re :Re: Re :Re: Bridging LACP (802.3ad) frames not working

[Ross Vandegrift]

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On Tue, Jan 12, 2010 at 09:40:30PM +0000, jhautbois@gmail.com wrote:
> This is exactly the problem.
> But, sounds like it is not possible... ?

You could run a custom version of the bridge driver to enable bridging
of frames sent to the bridge-management MAC addresses.  Some folks
have talked about doing similar things to enable bridging of STP.

Doing that with STP makes a bit more sense to me (since there are
valid networks that could be constructed that way).  But you'll be
breaking a pretty fundamental assumption of LACP....

-- 
Ross Vandegrift
ross@kallisti.us

"If the fight gets hot, the songs get hotter.  If the going gets tough,
the songs get tougher."
	--Woody Guthrie

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Re: [Bridge] Re :Re: Re :Re: Bridging LACP (802.3ad) frames not working

[Stephen Hemminger]

On Tue, 12 Jan 2010 17:04:48 -0500
Ross Vandegrift <ross@kallisti.us> wrote:

> On Tue, Jan 12, 2010 at 09:40:30PM +0000, jhautbois@gmail.com wrote:
> > This is exactly the problem.
> > But, sounds like it is not possible... ?
> 
> You could run a custom version of the bridge driver to enable bridging
> of frames sent to the bridge-management MAC addresses.  Some folks
> have talked about doing similar things to enable bridging of STP.
> 
> Doing that with STP makes a bit more sense to me (since there are
> valid networks that could be constructed that way).  But you'll be
> breaking a pretty fundamental assumption of LACP....

Recent kernels will forward link local frames as long as STP is disabled.
Older kernels will not.

The assumption is that if STP is enabled, then it will be managing
control plane.

Author: Stephen Hemminger <shemminger@vyatta.com>  2009-05-14 23:10:13
Committer: David S. Miller <davem@davemloft.net>  2009-05-17 21:12:54
Parent: 43aa1920117801fe9ae3d1fad886b62511e09bee (bridge: handle process all link-local frames)
Branches: master, remotes/origin/master
Follows: v2.6.30-rc6
Precedes: v2.6.30-rc7

    bridge: relay bridge multicast pkgs if !STP
    
    Currently the bridge catches all STP packets; even if STP is turned
    off.  This prevents other systems (which do have STP turned on)
    from being able to detect loops in the network.
    
    With this patch, if STP is off, then any packet sent to the STP
    multicast group address is forwarded to all ports.
    
    Based on earlier patch by Joakim Tjernlund with changes
    to go through forwarding (not local chain), and optimization
    that only last octet needs to be checked.
    
    Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>


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