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Date:	Mon, 19 May 2014 10:46:46 +0200
From:	Yegor Yefremov <>
To:	Mugunthan V N <>
Cc:	David Miller <>, netdev <>
Subject: Re: [net PATCH 1/1] drivers: net: cpsw: Add default vlan for dual
 emac case also

On Mon, May 5, 2014 at 4:20 PM, Mugunthan V N <> wrote:
> On Friday 02 May 2014 02:28 PM, Yegor Yefremov wrote:
>> On Wed, Apr 16, 2014 at 3:58 PM, Yegor Yefremov
>> <> wrote:
>>> On Wed, Apr 16, 2014 at 7:57 AM, Mugunthan V N <> wrote:
>>>> On Tuesday 15 April 2014 07:16 PM, Yegor Yefremov wrote:
>>>>> On Wed, Apr 9, 2014 at 8:56 PM, David Miller <> wrote:
>>>>>> From: Mugunthan V N <>
>>>>>> Date: Wed, 9 Apr 2014 11:34:40 +0530
>>>>>>> Dual EMAC works with VLAN segregation of the ports, so default vlan needs
>>>>>>> to be added in dual EMAC case else default vlan will be tagged for all
>>>>>>> egress packets and vlan unaware switches/servers will drop packets
>>>>>>> from the EVM.
>>>>> Hi Mugunthan,
>>>>> though this patch fixes drop packets issue, it introduces another
>>>>> issue. Just connect both interfaces to one switch and configure
>>>>> different subnets. As soon as you get a broadcast you have an endless
>>>>> loop and network communication is not possible at all. Before this
>>>>> patch you could operate as if you had really two independent NICs.
>>>> This patch doesn't add any multicast or unicast entry in the ALE table,
>>>> so there is no possible way that a broadcast packet is switched within
>>>> the two external ports, and this patch removes the encapsulation of the
>>>> default vlan id which is used for internal packet switching inside CPSW
>>>> switch from host and any packet received from external port will be
>>>> tagged with port vlan so internal switching will happen with that port
>>>> vlan-id which will be only that physical port and host port. so the
>>>> scenario which you mentioned cannot happen theoretically untill you
>>>> enable bridge between the dual ethernet interface and connect both to
>>>> the same interface.
>>> Have you tried the described setup? My system is Buildroot on
>>> am335x-evmsk with almost empty /etc/network/interfaces
>>> # Configure Loopback
>>> auto lo
>>> iface lo inet loopback
>>> No bridges:
>>> # brctl show
>>> bridge name     bridge id               STP enabled     interfaces
>>> And following address setup made manually:
>>> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
>>> group default
>>>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>>>     inet scope host lo
>>>        valid_lft forever preferred_lft forever
>>> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
>>> state UP group default qlen 1000
>>>     link/ether 00:18:31:93:f6:49 brd ff:ff:ff:ff:ff:ff
>>>     inet brd scope global eth0
>>>        valid_lft forever preferred_lft forever
>>> 3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast
>>> state DOWN group default qlen 1000
>>>     link/ether 56:90:76:5b:b5:f3 brd ff:ff:ff:ff:ff:ff
>>>     inet brd scope global eth1
>>>        valid_lft forever preferred_lft forever
>>> 4: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group
>>> default qlen 1000
>>>     link/ether de:ad:be:ef:00:00 brd ff:ff:ff:ff:ff:ff
>>> Routing table:
>>> # ip route show
>>> dev eth0  proto kernel  scope link  src
>>> dev eth1  proto kernel  scope link  src
>>> Same behavior on 3.14.0-rc4-12740-gcc09039-dirty and 3.15.0-rc1-00002-ge0f8779
>>> As soon as insert the cable into eth1, my switch shows very high
>>> activity and the whole LAN in the company is dead till I remove the
>>> cable. I have no problems with the version before the fix. I don't
>>> really know, what happens inside the driver, but could make the same
>>> setup (best of all in a LAN with many Windows PCs, that send lots of
>>> broadcast) and let me know if you see the same behavior.
>> This bug seems to be in 3.12 too. See this thread
>> (
>> Thanks.
>> Yegor
> Will check this in this week.

Any news concerning this issue?


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