Linux Ethernet Bridging - Apr 2007 - [BRIDGE]A basic question: what's the relationship of the Rx/Tx packets count between the bridge and its enslaved NIC.

On Tue, 16 Aug 2005 11:40:40 +0800
Steven Zhang <zhangseven@gmail.com> wrote:
> I have a bridge br0, it enslaves two NICs: eth0 and eth1. 
> By using "cat /proc/net/dev ", i can see the Rx/Tx packets and
bytes
> through each interface. just like this:

> I wonder the meaning of the value of the br0,  it's Rx/Tx packets is
> less than both eth0 and eth1.
> what's the relationship of the values between bridge and it's
enslaved NIC?
> 
The pseudo-device br0 is used for locally generated traffic

There will be several possible flows through a bridge:

Traffic going from 
	eth0 to eth1 will increase eth0:Rx and eth1:Tx
	eth1 to eth0               eth1:Rx     eth0:Tx
Locally transmits to eth0          br0:Tx  and eth0:Tx
Locally received via eth0          br0:Rx  and eth0:Rx

Also, packets generated locally with unknown destination
will be flooded to both eth0 and eth1.

You get the idea

I have a bridge br0, it enslaves two NICs: eth0 and eth1. 
By using "cat /proc/net/dev ", i can see the Rx/Tx packets and bytes
through each interface. just like this:

[* time tick 1 *]

Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed
multicast|bytes    packets errs drop fifo colls carrier compressed
    lo: 3926521   14121    0    0    0     0          0         0 
3926521   14121    0    0    0     0       0          0
  eth0: 7255431   37878    0    0    0     0          0         0
12869195   26229    0    0    0     0       0          0
  eth1:12172910   25800    3    3    0     3          0         0 
7849528   38567   72    0    0     5      77          0
   br0: 3035036   17478    0    0    0     0          0         0 
2950728   12908    0    0    0     0       0          0
 
[* time tick 2 *]

Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed
multicast|bytes    packets errs drop fifo colls carrier compressed
    lo: 4020580   14734    0    0    0     0          0         0 
4020580   14734    0    0    0     0       0          0
  eth0: 7780868   41663    0    0    0     0          0         0
17450012   30518    0    0    0     0       0          0
  eth1:16759363   30073    3    3    0     3          0         0 
8375862   42391   72    0    0     5      77          0
   br0: 3086377   17819    0    0    0     0          0         0 
2986052   13185    0    0    0     0       0          0

[* the delta value *]

Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed
multicast|bytes    packets errs drop fifo colls carrier compressed
    lo:   94059     613    0    0    0     0          0         0   
94059     613    0    0    0     0       0          0
  eth0:  525437    3785    0    0    0     0          0         0 
4580817    4289    0    0    0     0       0          0
  eth1: 4586453    4273    0    0    0     0          0         0  
526334    3824    0    0    0     0       0          0
   br0:   51341     341    0    0    0     0          0         0   
35324     277    0    0    0     0       0          0

I wonder the meaning of the value of the br0,  it's Rx/Tx packets is
less than both eth0 and eth1.
what's the relationship of the values between bridge and it's enslaved
NIC?

Thanks for your comments on this.