[c-nsp] Using DFC cards on a L2 6500/7600 system

[Tassos Chatzithomaoglou]

Sorry Tim, but more questions came up now...


7600-ES20 datasheets say something about 80.000 mac addresses per ES card.

What is the catch here? How can the SUP720 know n * 80k addresses when it only supports 64k?
Does it refer to mac addresses belonging to per card locally configured vlans only?


Also, on a system with DFC modules "sh mac-address-table count" shows only the macs "known" by the SUP720.


7609#sh mac-address-table count
MAC Entries  for all vlans :
Dynamic Address Count:                71
Static Address (User-defined) Count:  113
Total MAC Addresses In Use:           184
Total MAC Addresses Available:        65536

DFC module
----------
7609#sh mac-address-table count mod 1
MAC Entries for module 1 :
Dynamic Address Count:                2031
Static Address (User-defined) Count:  113
Total MAC Addresses In Use:           2144
Total MAC Addresses Available:        65536

DFC module
----------
7609#sh mac-address-table count mod 2
MAC Entries for module 2 :
Dynamic Address Count:                1697
Static Address (User-defined) Count:  113
Total MAC Addresses In Use:           1810
Total MAC Addresses Available:        65536

SUP720 (same as the 1st one)
---------------------------
7609#sh mac-address-table count mod 6
MAC Entries for module 6 :
Dynamic Address Count:                71
Static Address (User-defined) Count:  113
Total MAC Addresses In Use:           184
Total MAC Addresses Available:        65536


I guess that's because mac sync between DFC & PFC is disabled by default (SXF8). Any reason to keep it disabled?
http://www.ciscotaccc.com/kaidara-advisor/lanswitching/showcase?case=K63315572 says it's better to enable it, but why isn't is so 
by default (besides X6708-10GE)?
Also "mac-address-table synchronize" doesn't seem to provide any option for (dis)activation per DFC module.
So if i have a vlan used only locally in a DFC module, can i keep the sync disabled in that module in order to save some mac space?

Regards,
Tassos

>>
>> You said that each DFC equipped module has its own mac address table. 
>> So i can have 9 x 65536 (or 64000) macs per 6509?
> 
> No, sorry to mislead you. While you could actually have as many as 17 
> unique L2 engines in the system (DFC3B/BXL has 2 L2 engines, one for 
> each 1/2 of the card), each w/their own copy of the MAC table, there are 
> actually hw mechanisms (and sw mechanisms w/the sync command I 
> mentioned) in place to try to keep them in sync, and as such you can't 
> scale n * 64K MAC entries, we still advertise 64K for the system.
> 
> Reason being, a FE on one card needs to know about all the other MACs in 
> the system in case it gets a frame destined to one of those MACs; else, 
> you'll get flooding. Yes there are certain cases where in theory you 
> could scale the MACs (vlan only on one FE, etc) but these have never 
> been developed.
> 
> So for now, for all practical purposes, the MAC table is synched on all 
> cards.
> 

> 
> 
> Tim Stevenson, tstevens at cisco.com
> Routing & Switching CCIE #5561
> Technical Marketing Engineer, Data Center BU
> Cisco Systems, http://www.cisco.com
> IP Phone: 408-526-6759
> ********************************************************
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