EtherChannel: Cisco-proprietary hash algorithm
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Posted by Miguel Sanders on August 19, 2008, 1:50 pm
Please log in for more thread options Hello folks I have been implementing an EtherChannel on my 3750E switches based on source/destination IP address hashing. I have found documents that explain the hashing algorithm for layer 2 load balancing based on source/destination MAC addresses. However, does someone know how the algorithm works for source/ destination IP address hashing? If so, could you explain how this works? Thanks a lot! Miguel | |||||||||||||||||||
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Posted by Gabriele Beltrame on August 20, 2008, 8:49 am
Please log in for more thread options Hi, CEF Load Sharing algorythm maps destination prefixes to a maxiumum of 16 paths; an hash function then assign source-destination pairs to a particular path. You can have a look at the distribution using "sh ip cef <prefix> internal"
There are actually three different algorithms available: the standard/old one, the "universal" and a "tunnel tuned" version. The Universal algorithm is seeded, so each router can have different hash results and the traffic is more evenly spread among the internetwork Regards, Gabriele | |||||||||||||||||||
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Posted by on August 20, 2008, 12:29 pm
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>
> > Hello folks
>
> > I have been implementing an EtherChannel on my 3750E switches based on
> > source/destination IP address hashing. I have found documents that > > explain the hashing algorithm for layer 2 load balancing based on > > source/destination MAC addresses. > > However, does someone know how the algorithm works for source/ > > destination IP address hashing? > > If so, could you explain how this works? >
> > Thanks a lot!
>
> > Miguel
>
> Hi, > > CEF Load Sharing algorythm maps destination prefixes to a maxiumum of 16 > paths; an hash function then assign source-destination pairs to a particular > path. > You can have a look at the distribution using "sh ip cef <prefix> internal" > > There are actually three different algorithms available: the standard/old > one, the "universal" and a "tunnel tuned" version. > The Universal algorithm is seeded, so each router can have different hash > results and the traffic is more evenly spread among the internetwork That is interesting, but it is not related to the etherchannel load distribution algorithm. http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_44_se/configuration/guide/swethchl.html#wp1275731 Section "Load Balancing and Forwarding Methods" To the OP - if you can't find anything in the documentation and have support consider a TAC case. It is possible that cisco regard the algorithm as a trade secret and they may not be prepared to release it. | |||||||||||||||||||
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Posted by Miguel Sanders on August 21, 2008, 1:00 pm
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On 20 aug, 18:29, Bo...@hotmail.co.uk wrote: >
> > > > > > > > Hello folks
>
> > > I have been implementing an EtherChannel on my 3750E switches based on
> > > source/destination IP address hashing. I have found documents that > > > explain the hashing algorithm for layer 2 load balancing based on > > > source/destination MAC addresses. > > > However, does someone know how the algorithm works for source/ > > > destination IP address hashing? > > > If so, could you explain how this works? >
> > > Thanks a lot!
>
> > > Miguel
>
> > Hi,
>
> > CEF Load Sharing algorythm maps destination prefixes to a maxiumum of 16
> > paths; an hash function then assign source-destination pairs to a particular > > path. > > You can have a look at the distribution using "sh ip cef <prefix> internal" >
> > There are actually three different algorithms available: the standard/old
> > one, the "universal" and a "tunnel tuned" version. > > The Universal algorithm is seeded, so each router can have different hash > > results and the traffic is more evenly spread among the internetwork >
niet weergeven -
> That is interesting, but it is not related to the > etherchannel load distribution algorithm. > > http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/re... > > Section "Load Balancing and Forwarding Methods" > > To the OP - if you can't find anything in the documentation > and have support consider a TAC case. > It is possible that cisco regard the algorithm as a trade secret > and they may not be prepared to release it.- Tekst uit oorspronkelijk bericht >
> - Tekst uit oorspronkelijk bericht weergeven - That's funny because they do give it for load balancing based on layer 2 data (MAC address). http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml Nevertheless, it should be a simple operation since it has to be done very quick in the hardware. Any tips on this would be much appreciated. | |||||||||||||||||||
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Posted by Stephen on August 21, 2008, 5:37 pm
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On Tue, 19 Aug 2008 10:50:12 -0700 (PDT), Miguel Sanders >Hello folks
> >I have been implementing an EtherChannel on my 3750E switches based on >source/destination IP address hashing. I have found documents that >explain the hashing algorithm for layer 2 load balancing based on >source/destination MAC addresses. this doc implies they use the same algorithm whether it is working on L2 or L3. http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml#catalyst >However, does someone know how the algorithm works for source/
--
>destination IP address hashing? >If so, could you explain how this works? > > >Thanks a lot! > >Miguel Regards stephen_hope@xyzworld.com - replace xyz with ntl | |||||||||||||||||||
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>
> I have been implementing an EtherChannel on my 3750E switches based on
> source/destination IP address hashing. I have found documents that
> explain the hashing algorithm for layer 2 load balancing based on
> source/destination MAC addresses.
> However, does someone know how the algorithm works for source/
> destination IP address hashing?
> If so, could you explain how this works?
>
>
> Thanks a lot!
>
> Miguel