Question: eth0 and wlan0 traffic load

Question: eth0 and wlan0 traffic load

[Lin Ming]

On Host1
  eth0: 192.168.1.102
wlan0: 192.168.1.103

On Host2, scp a file to Host1 via wlan0
# scp tmp.file 192.168.1.103:/tmp

But ifstat shows all traffic goes to eth0.
Why does kernel choose eth0 although I use wlan0's address?
Is this an intended behavior?

       eth0               wlan0
 KB/s in  KB/s out   KB/s in  KB/s out
11989.26    286.05      0.00      0.00
11998.90    286.00      0.00      0.00
 6910.18    170.63      0.00      0.00
10260.05    246.82      0.00      0.00
 8295.90    202.12      0.00      0.00
11979.90    282.41      0.00      0.00
11618.39    274.71      0.00      0.00
 7004.78    170.79      0.00      0.00
12003.33    286.21      0.00      0.00
 7775.28    190.59      0.00      0.00
11980.18    280.76      0.00      0.00
11998.32    286.29      0.00      0.00
11995.61    286.08      0.00      0.00
11996.57    285.88      0.00      0.00
 6938.20    162.98      0.00      0.00
 6736.30    169.22      0.04      0.00
12000.92    284.83      0.00      0.00
12005.41    286.13      0.00      0.00
12000.58    286.27      0.00      0.00
11963.65    284.13      0.00      0.00
11935.24    281.32      0.00      0.00
12002.83    286.27      0.00      0.00
11997.59    285.68      0.00      0.00

Thanks,
Lin Ming

Re: Question: eth0 and wlan0 traffic load

[Ben Greear]

On 07/06/2012 08:28 PM, Lin Ming wrote:
> On Host1
>    eth0: 192.168.1.102
> wlan0: 192.168.1.103
>
> On Host2, scp a file to Host1 via wlan0
> # scp tmp.file 192.168.1.103:/tmp
>
> But ifstat shows all traffic goes to eth0.
> Why does kernel choose eth0 although I use wlan0's address?
> Is this an intended behavior?

You have to be clever with routing rules, arp-filtering, and such
to ensure that works as you want.

Thanks,
Ben

>
>         eth0               wlan0
>   KB/s in  KB/s out   KB/s in  KB/s out
> 11989.26    286.05      0.00      0.00
> 11998.90    286.00      0.00      0.00
>   6910.18    170.63      0.00      0.00
> 10260.05    246.82      0.00      0.00
>   8295.90    202.12      0.00      0.00
> 11979.90    282.41      0.00      0.00
> 11618.39    274.71      0.00      0.00
>   7004.78    170.79      0.00      0.00
> 12003.33    286.21      0.00      0.00
>   7775.28    190.59      0.00      0.00
> 11980.18    280.76      0.00      0.00
> 11998.32    286.29      0.00      0.00
> 11995.61    286.08      0.00      0.00
> 11996.57    285.88      0.00      0.00
>   6938.20    162.98      0.00      0.00
>   6736.30    169.22      0.04      0.00
> 12000.92    284.83      0.00      0.00
> 12005.41    286.13      0.00      0.00
> 12000.58    286.27      0.00      0.00
> 11963.65    284.13      0.00      0.00
> 11935.24    281.32      0.00      0.00
> 12002.83    286.27      0.00      0.00
> 11997.59    285.68      0.00      0.00
>
> Thanks,
> Lin Ming
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-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Question: eth0 and wlan0 traffic load

[Lin Ming]

On Sat, Jul 7, 2012 at 12:16 PM, Ben Greear <greearb@candelatech.com> wrote:
> On 07/06/2012 08:28 PM, Lin Ming wrote:
>>
>> On Host1
>>    eth0: 192.168.1.102
>> wlan0: 192.168.1.103
>>
>> On Host2, scp a file to Host1 via wlan0
>> # scp tmp.file 192.168.1.103:/tmp
>>
>> But ifstat shows all traffic goes to eth0.
>> Why does kernel choose eth0 although I use wlan0's address?
>> Is this an intended behavior?
>
>
> You have to be clever with routing rules, arp-filtering, and such
> to ensure that works as you want.

Ah, right.
The arp cache on Host2 for .102 and .103 points to Host1's eth0.

Host2 # arp -a
chief-river-32.local (192.168.1.102) at 00:1c:c4:a4:33:9e [ether] on eth0
chief-river-32.local (192.168.1.103) at 00:1c:c4:a4:33:9e [ether] on eth0

Thanks,
Lin Ming