Re: [LARTC] TEQL questions

[Stef Coene <stef.coene@docum.org>]

I never tried it myself, but I found this in the kernel sources :

Short description:
------------------

                  +-------+   eth1   +-------+
                  |       |==========|       |
  'network 1' ----|   A   |          |   B   |---- 'network 2'
                  |       |==========|       |
                  +-------+   eth2   +-------+

   Router A and B are connected to each other with two links.
   The device to be set up is basically a roundrobbin distributor
   over eth1 and eth2, for sending packets. No data ever comes in
   over an teql device, that just appears on the 'raw' eth1 and eth2.
   But now we just have devices, we also need proper routing. One way
   to do this is to assign a /31 network to both links, and a /31 to
   the teql0 device as well. That means, we have to have a transfer
   network for this.

   Routing:  eth1_A: 10.0.0.0/31
             eth1_B: 10.0.0.1/31

             eth2_A: 10.0.0.2/31
             eth2_B: 10.0.0.3/31

             teql0_A: 10.0.0.4/31
             teql0_B: 10.0.0.5/31

             If you only have Linux boxes on each side, you can use /31
             as subnet and so you can avoid wasting IP-Addresses for
             broadcast and network addresses

   You have to set up the IP-Addresses accordingly. Your default gw
   should point to teql0.

   In order to use this feature TEQL must be enables in your kernel.
   You have to set up this framework on both sides (ie. Router A and B).

CAVEATS:
--------

  You have to disable Reverse Path Filtering! Ie. I guess you do not want
  to use this in a Firewall/DMZ area. :-)
  Then there is the nasty problem of packet reordering. Let's say 6 packets
  need to be sent from A to B - eth1 might get 1, 3 and 5. eth2 would then
  do 2, 4 and 6. In an ideal world, router B would receive this in order,
  1, 2, 3, 4, 5, 6. But the possibility is very real that the kernel gets
  it like this: 2, 1, 4, 3, 6, 5. The problem is that this confuses TCP/IP.
  While not a problem for links carrying many different TCP/IP sessions,
  you won't be able to to a bundle multiple links and get to ftp a single
  file lots faster, except when your receiving or sending OS is Linux,
  which is not easily shaken by some simple reordering.


Stef

On Wednesday 20 February 2002 22:58, you wrote:
> Hi All -
>
> I've decided that TEQL will meet my needs. I am having a problem with it
> now and I have not been able to find any documentation in regards to
> this.
>
> I have added both of my interfaces (on both ends of the connections) to
> the teql0 interface:
>
> tc qdisc add dev eth1 root teql0
> tc qdisc add dev eth2 root teql0
>
> I did this for both ends and assigned an ip address to teql0 on both
> ends of 172.16.3.1/29 and 172.16.3.2/29 respectivly.
>
> ip addr add dev teql0 172.16.3.1/29
> ip addr add dev teql0 172.16.3.2/29
>
>
> I cannot get them to ping, I get Network is unreachable.
>
> I am I missing something ?
>
> I have the ip addresses of 172.16.2.1/29 + 172.16.1.2/29 on one box and
> 172.16.2.2/29 + 172.16.1.1/29 on the other machine. These links can see
> each other fine.
>
> Thanks in advance for any help.
>
> - Chris

-- 

stef.coene@docum.org
 More QOS info : http://www.docum.org/
 Title : "Using Linux as bandwidth manager"
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