Cisco WS-X6748 Port-ASIC mapping

Unanswered Question
Jun 30th, 2010

Hi Experts,

I am using 6509 Switch installed with WS-X6748-SFP module. I used the command "show interface gigabitethernet 1/1 capablities". I am seeing a lot of stuffs in the output. One thing which interested me is "Ports-in-ASIC (Sub-port ASIC)" information. Find the attached command output file.

Ports-in-ASIC (Sub-port ASIC) : 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47 (1,3,5,7,9,11,13,15,17,19,21,23)

Roughly i understood that One ASIC Port is shared with multiple Physical Ethernet ports.

I request your help to understand it more and provide me how it is oversubscribed. I checked in various documents, I am missing to get a good one

thnks in advance

Sairam

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snarayanaraju Fri, 07/02/2010 - 00:44

Hi Friends,

I hope this query is not answered may be kept unnoticed.

I appreciate your help in clarifying this

regards,

sairam

vladimirsaltao Fri, 07/02/2010 - 01:36

I think this explains it very well

"On switches a lot of port hardware is based on asics which control 4-8 ports on a slot . Each of the asics has a certain amount of bandwidth to the backplane of the switch . If a asic has a 4 gig backplane bandwidth but there  8 1 gig ports on that asic  then those group of ports are oversubscribed for those given ports .  This is only an issue if you get more than 4 of those connections running a full gig  and is what cisco bets on when designing their switches this way ." . In your case you should try to see (or maybe some expert can give us this info) whats the bandwith of the connection to the backplane in that module to see how much oversubscrition there is

jorge.calvo Fri, 07/02/2010 - 04:22

Hello,

The WS-X6748-SFP module has 3 levels of ASICs:

- Bus and Fabric ASICs : JANUS (x2) and SSA (x2)

- Port ASICs: ROHINI (x4)

Each ROHINI ASIC manages 12 GE ports and the recommended design oversubscription when this module is used on a Data Center is 1:2:1.

Hope this helps.

jorge.calvo Thu, 10/28/2010 - 16:01

Hi,

Actually it was a typo...I meant 1.2:1 --> 48 Gbps ports with 20 Gbps connection to the fabric (if you use a SUP720).

Cheers.

Jon Marshall Thu, 10/28/2010 - 16:10

jorge.calvo wrote:

Hi,

Actually it was a typo...I meant 1.2:1 --> 48 Gbps ports with 20 Gbps connection to the fabric (if you use a SUP720).

Cheers.

Jorge

Sorry, did you mean 24Gbps ports with 20Gbps connection to fabric which is 1.2:1  ? as that module has 2 x 20Gbps conection to switch fabric.

Jon

Atif Awan Thu, 10/28/2010 - 21:19

jon.marshall wrote:

jorge.calvo wrote:

Hi,

Actually it was a typo...I meant 1.2:1 --> 48 Gbps ports with 20 Gbps connection to the fabric (if you use a SUP720).

Cheers.

Jorge

Sorry, did you mean 24Gbps ports with 20Gbps connection to fabric which is 1.2:1  ? as that module has 2 x 20Gbps conection to switch fabric.

Jon

It is indeed 24 ports to a 20-Gig channel.

Atif

jorge.calvo Fri, 10/29/2010 - 03:27

Yes Jon,

It can be expressed as 24 x 1Gbps ports pors per 1 x 20Gbps Junos ASIC --> 1.2:1

Or

48 x 1Gpbs ports pero 1 x 20Gbps Junos ASIC --> 2.4:1 and having 2 Junos --> 1.2:1

Sorry for not being clear enough.

Cheers

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