hp procurve 54XX and 82XX module local switching ?

[pdvfried]

Hello all

Is local switching on the zl modules ( procurve 54XX and 82XX) supported?

That means :  traffic from port 1 to port 2 of the same module will be  local switched on the module,  or has to be forwarded to the fabric?

Thanks a lot

pdvfried

[jefflj]

the last time I checked, the 5400 and the 8200 all use local switching.  The only time a packet is forwarded to the backplane is if the destination is not  on the local blade.

[Pete W · Accepted solution]

Interestingly, I asked an "HP Networking Solution Architect" the exact same question last year and got completely the opposite answer. I was told that:

On the 5400 / 8200 zl switch, all traffic must be switched or routed to the fabric module EVERY TIME. Its not like 6500 with DFC cards, or even the 7500 where once the initial lookup is done it can stay within the card. This is a deliberate ASIC design. 

And looking at the quickspec document for the 5400zl, it reads:

High-speed, high-capacity architecture : 1 Tbps crossbar switching fabric provides intra-module and inter-module switching with 585.6 million pps throughput on the purpose-built ProVision ASICs.

... implying that it is the responsibility of the backplane crossbar fabric to provide intra-module communications (i.e. frames have to leave the module and transit the crossbar in order to go back in).

And looking at http://h20195.www2.hp.com/v2/GetPDF.aspx/4AA0-5388ENW.pdf (which covers the ProVision Architecture), it mentions on page 9:

Fabric Interface
After the packet header leaves the programmable section, the header is forwarded to the Fabric Interface.
The Fabric Interface makes final adjustments to the header, based on priority information, multicast grouping,
and so on, and then uses this header to modify the actual packet header as necessary.
The Fabric Interface then negotiates with the destination ProVision ASICs for outbound packet buffer space.
If congestion is present on the outbound port, weighted random early detection can be applied at this point as a
congestion-avoidance mechanism. Finally, the ProVision ASICs’ Fabric Interface forwards the entire packet through
the Fabric-ASIC to an awaiting output buffer on the ProVision ASICs that controls the outbound port for the packet.
Packet transfer from the ProVision ASICs to the Fabric-ASIC is accomplished using the full-duplex backplane
connection, also managed by the Fabric Interface. The full-duplex backplane connection is 28.8 Gbps with standard
zl modules, 46.8 Gbps with 8200 zl switches, and 31.6 Gbps with 5400 zl switches.

The above states that the packet is forwarded through the switch's backplane, however this is obviously an inter-module (and not intra-module) senario - so I'm not 100% sure again :).

PRW