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Date:	Mon, 5 May 2014 19:50:56 +0530
From:	Mugunthan V N <>
To:	Yegor Yefremov <>
CC:	David Miller <>, netdev <>
Subject: Re: [net PATCH 1/1] drivers: net: cpsw: Add default vlan for dual
 emac case also

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.

Mugunthan V N
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