Re: Strange multi-interface workings

[Jeff Garzik]

This is a multi-part message in MIME format.
--------------C2926A01A2E6D8645A3E53A3
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

"David S. Miller" wrote:
> 
> Can you show the routing tables?  They are all on the same network,
> so the kernel can choose whichever interface it pleases to send the
> packets out, and if your routing tables are how I believe they are,
> the kernel isn't making new 10.10.10.0 network destination routes
> for eth1 and eth2 because one already exists for eth0.

(routing table is first attachment, below)

Given that there is a network route for each eth interface I was
surprised when the traffic starting "migrating" to another interface.

The reason I think this is a problem is because it seems to break the
theory that multiple interfaces can help speed things up -- I ran
ApacheBench (ab) against 10.10.10.133 (eth1) and 10.10.10.134 (eth2),
but ifconfig only shows eth0 and eth1 as receiving packets.

Is there a sysctl or similar setting which will allow me to at least
advertise all three interfaces via arp?  Since the machine advertises
the same ethernet address for .133 and .134, it is rather tough to test
10.10.10.134 (eth2) at all.

> I think you need to do a tiny bit of study on how IP routing
> works :-)

I don't doubt that at all..... :)

Though it seems really bogus to send packets to 10.10.10.134, eth2, only
to have them received by eth1.  That would seem to break network load
balancing by admins who use multiple NICs.

	Jeff

-- 
Jeff Garzik         | "Vegetarian" is the Indian word
Building 1024       | for 'lousy hunter.'
MandrakeSoft, Inc.  |
--------------C2926A01A2E6D8645A3E53A3
Content-Type: text/plain; charset=us-ascii;
 name="netstat.txt"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="netstat.txt"

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.10.10.134    0.0.0.0         255.255.255.255 UH       40 0          0 eth2
10.10.10.133    0.0.0.0         255.255.255.255 UH       40 0          0 eth1
10.10.10.100    0.0.0.0         255.255.255.255 UH       40 0          0 eth0
10.10.10.0      0.0.0.0         255.255.255.0   U        40 0          0 eth0
10.10.10.0      0.0.0.0         255.255.255.0   U        40 0          0 eth1
10.10.10.0      0.0.0.0         255.255.255.0   U        40 0          0 eth2
127.0.0.0       0.0.0.0         255.0.0.0       U        40 0          0 lo
0.0.0.0         10.10.10.1      0.0.0.0         UG       40 0          0 eth0

--------------C2926A01A2E6D8645A3E53A3
Content-Type: text/plain; charset=us-ascii;
 name="ifconfig.txt"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="ifconfig.txt"

eth0      Link encap:Ethernet  HWaddr 00:40:F6:F4:FF:EF  
          inet addr:10.10.10.100  Bcast:10.10.10.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:28441 errors:0 dropped:0 overruns:0 frame:0
          TX packets:40635 errors:0 dropped:0 overruns:0 carrier:0
          collisions:1401 txqueuelen:100 
          Interrupt:19 

eth1      Link encap:Ethernet  HWaddr 00:40:F6:F4:FF:73  
          inet addr:10.10.10.133  Bcast:10.10.10.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:13109 errors:0 dropped:0 overruns:0 frame:0
          TX packets:32 errors:0 dropped:0 overruns:0 carrier:0
          collisions:1 txqueuelen:100 
          Interrupt:18 

eth2      Link encap:Ethernet  HWaddr 00:00:21:DC:5A:9A  
          inet addr:10.10.10.134  Bcast:10.10.10.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:304 errors:0 dropped:0 overruns:0 frame:0
          TX packets:31 errors:0 dropped:0 overruns:0 carrier:0
          collisions:1 txqueuelen:100 
          Interrupt:17 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:3924  Metric:1
          RX packets:130 errors:0 dropped:0 overruns:0 frame:0
          TX packets:130 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 

--------------C2926A01A2E6D8645A3E53A3
Content-Type: text/plain; charset=us-ascii;
 name="arp.txt"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="arp.txt"

? (10.10.10.100) at 00:40:F6:F4:FF:EF [ether] on eth0
? (10.10.10.1) at 00:40:05:17:92:0B [ether] on eth0
? (10.10.10.166) at 00:A0:CC:50:E4:4C [ether] on eth0
? (10.10.10.133) at 00:40:F6:F4:FF:73 [ether] on eth0
? (10.10.10.134) at 00:40:F6:F4:FF:EF [ether] on eth0

--------------C2926A01A2E6D8645A3E53A3--