Re: Internet Traffic load balancing

This is one of the most amazing threads on Group Study in a long while
:-). I just had to say it!

--
Marko Milivojevic - CCIE #18427
Senior Technical Instructor - IPexpert
FREE CCIE training: http://bit.ly/vLecture
Mailto: markom_at_ipexpert.com
Telephone: +1.810.326.1444
Web: http://www.ipexpert.com/
On Tue, May 3, 2011 at 09:16, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:
> Marko,
> I made a small test and the thing makes for a lot of fun (and food for
> thought for a R/S expert :)
>
> I have one generator (ostinato), sending steady traffic to 10 different
> addresses, 1.1.1.1 .. 10.10.10.10 (@1000 pps) to a router R1 which has
> 2 serials connected to router R2 acting as a sink.
> (Actually sending pings, so the sink is answering back)
>
> Serial links are 20.1.1.0/30 and 20.2.2.0/30, generated 10 statics to
> 0.0.0.0/0 via 169.254.1.1 .. 7 and 169.254.2.1 .. 3, and respective
> recursive routes to s0/0 and s0/1.
>
> SNMP in R1 shows more or less balanced traffic :(
> Hmm, I got 2 routes out (so ended with 8:1) and all traffic went to one
> interface! What ? Added a second route and I got a 5:2 relation.
> Aha. The 10 different destinations are not getting into 10 different
> CEF hash buckets!
>
> R1 is a 2610XM running 12.4.9T7.
> I played with "ip cef load-sharing algorithm" and the load changes.
>
> So my readings:
>
> works ? yes. (unequal load balancing using CEF, seeded by statics)
> is obvious how ? Not at all.
>
> This version does not has 16 fixed buckets as Ivan documents:
>
> R1#sh ip cef 0.0.0.0 0.0.0.0 internal
> *Jul B 1 12:30:36.866: %SYS-5-CONFIG_I: Configured from console by console
> 0.0.0.0/0, version 50, epoch 0, per-destination sharing
> 0 packets, 0 bytes
> B via 169.254.2.2, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.2.2.2, Serial0/1 via 169.254.2.2/32
> B  B valid adjacency
> B via 169.254.2.1, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.2.2.2, Serial0/1 via 169.254.2.1/32
> B  B valid adjacency
> B via 169.254.1.7, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.7/32
> B  B valid adjacency
> B via 169.254.1.6, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.6/32
> B  B valid adjacency
> B via 169.254.1.5, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.5/32
> B  B valid adjacency
> B via 169.254.1.4, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.4/32
> B  B valid adjacency
> B via 169.254.1.3, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.3/32
> B  B valid adjacency
> B via 169.254.1.2, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.2/32
> B  B valid adjacency
> B via 169.254.1.1, 0 dependencies, recursive
> B  B traffic share 1
> B  B next hop 20.1.1.2, Serial0/0 via 169.254.1.1/32
> B  B valid adjacency
>
> B 0 packets, 0 bytes switched through the prefix
> B tmstats: external 0 packets, 0 bytes
> B  B  B  B  B  internal 0 packets, 0 bytes
> B Load distribution: 0 1 2 3 4 5 6 7 8 (refcount 1)
>
> B Hash B OK B Interface B  B  B  B  B  B  B  B  Address B  B  B  B  Packets
> B 1 B  B  Y B  Serial0/1 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 2 B  B  Y B  Serial0/1 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 3 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 4 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 5 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 6 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 7 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 8 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B 9 B  B  Y B  Serial0/0 B  B  B  B  B  B  B  B  point2point B  B  B  B  B  0
> B refcount 4318, covered prefixes:
> B  B 169.254.2.3/32
> B  B 169.254.2.2/32
> B  B 169.254.2.1/32
> B  B 169.254.1.7/32
> B  B 169.254.1.6/32
> B  B 169.254.1.5/32
> B  B 169.254.1.4/32
> B  B 169.254.1.3/32
> B  B 169.254.1.2/32
> B  B 169.254.1.1/32
> B  B 172.30.0.0/16
> B  B 20.2.2.0/30
> B  B 20.1.1.0/30
> B  B 224.0.0.0/4
> B  B 255.255.255.255/32
> B  B 0.0.0.0/32
> R1#
>
> -Carlos
>
>
>
> Marko Milivojevic @ 02/05/2011 22:39 -0300 dixit:
>>
>> On Mon, May 2, 2011 at 17:45, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:
>>>
>>> This was generated from the switching point ? I.e. it was generated by
>>> the
>>> router having the 5:2 statics ?
>>>
>>> I would test it from a neighbour, so CEF is used for sure. Local trafic
>>> is process switched most probably.
>>
>> Those are valid points, but are contrary to what was originally
>> expected. My argument was that CEF would break this, but I honestly
>> expected that it would work when process-switched. It doesn't seem to.
>> I will add 3rd router behind R2 and re-run the test.
>>
>> --
>> Marko Milivojevic - CCIE #18427
>> Senior Technical Instructor - IPexpert
>>
>> FREE CCIE training: http://bit.ly/vLecture
>>
>> Mailto: markom_at_ipexpert.com
>> Telephone: +1.810.326.1444
>> Web: http://www.ipexpert.com/
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
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>>
>>
>
> --
> Carlos G Mendioroz B <tron_at_huapi.ba.ar> B LW7 EQI B Argentina
Blogs and organic groups at http://www.ccie.net