[c-nsp] How does IOS do loadshaing with ECMP?

[Sukumar Subburayan]

For Sup720 a unique router-id will be used. You probably are thinking 
about Sup2, where router-id is not supported in HW.

Do a 'show ip cef summary' and you wil see something like an 'id <no>' in 
the output. The Sup720 HW switching used this ID part of the hash 
algorithm for the default srt+dstip based load-balancing.

Due to some internal Sup720 specific limitation for even paths (2,4,6,8 
etc..) we may have to add additional adjacencies to get even 
load-balancing. So, when simple is not configured, we will be adding these 
additional adjacencies to get even load balancing. BTW, this is the 
default for Sup720.

sukumar

PS: Please unicast me if you need more details.


On Tue, 21 Nov 2006, Joe Shen wrote:

> which router_id will be used to caculate hash result?
>
> I come to know that,  packets with the same (src_ip,
> dst_ip, src_port, dst_port) will follow the same
> routing path, and number of FIB entry is the same as
> those in RIB. But, if "simple" is not configured what
> entry will be added by HW ? why does IOS do that ?
>
> regards
>
> Joe
>
>
>> Sup720 supports load-balancing using
>> src_ip,dst_ip+universal_router_id and
>> this is the default.
>>
>> In this particular case below, you have:
>>
>> mls ip cef load-sharing full simple
>>
>> 'mls ip cef load-sharing full' lets you use
>> 'src_ip,dst_ip+l4 ports'
>> instead of the univeral_router_id
>>
>> However, the addition of 'simple' keyword, allows
>> hardware to use
>> the same number of adjacencies as in the IOS CEF
>> adjacency.
>>
>> Without the 'simple' keyword the HW installs
>> additional adjacency entries
>> to avoid platform polarization.
>>
>> sukumar
>>
>>
>>
>> On Mon, 20 Nov 2006, Phil Bedard wrote:
>>
>>> That command tells the box to use L4 port
>> information in making load
>>> balancing
>>> decisions.   I think if you just set that back to
>> the default it will
>>> only use
>>> the source/destination hash like you are used to.
>>>
>>> Phil
>>>
>>>
>>> On Nov 20, 2006, at 9:45 AM, Joe Shen wrote:
>>>
>>>> mls ip cef load-sharing full simple
>>>
>>>
>>>
>>> _______________________________________________
>>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
>>> https://puck.nether.net/mailman/listinfo/cisco-nsp
>>> archive at
>> http://puck.nether.net/pipermail/cisco-nsp/
>>>
>>
>
>
>
>
> ___________________________________________________________
> 雅虎免费邮箱-3.5G容量，20M附件
> http://cn.mail.yahoo.com/
>