Whats the difference...

Unanswered Question
Feb 10th, 2009

Between this


and this


Excluding the obvious price difference??



I have this problem too.
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Overall Rating: 4 (3 ratings)
dcpeterchin Tue, 02/10/2009 - 08:17

I think with the WS-X6148A-GE-TX model,

you can NOT enable jumbo frame on it. In

other words, jumbo frame is not supported

with this line card.

cpubob Tue, 02/10/2009 - 08:20

Check out this doc, both are listed.



Usage: Data center and server farm

Connectors: 48, RJ-45, 100m, Category 5 cable

PoE: No

Frame Size: Up to 9216 bytes per frame

Queues: Tx-1p3q8t; Rx-1q8t (when using Distributed Cisco Express Forwarding)

Buffer Size per port: 1.3 MB


Usage: Wiring closet

Connectors: 48, RJ-45, 100m, Category 5 cable

PoE: Field-upgradable to Cisco Prestandard and IEEE 802.3af

Frame Size: Up to 9216 bytes per frame

Queues: Tx-1p3q8t Rx-1q2t

Buffer Size per port: 5.5 MB



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peterlmyers Tue, 02/10/2009 - 08:41

Hi Stephen,

It's all about backplane speed. The 6748 is fabric enabled and can connect to the switch backplane at 40gbps. The 6148 on the other hand only connects to the backplane at 8gbps. Hence the descriptions of wiring closest/data center.

Hope this helps


stephen.stack Tue, 02/10/2009 - 10:17

Hi Guys,

Thanks for the great responses. I guess i'll have to go and have a ggod long think about this then. It is our core switches that need upgrading. Cost Vs Performance???


adamclarkuk_2 Tue, 02/10/2009 - 11:39

Hi Stephen

If you make your decision based on the speed of the uplink to the backplane, you need to make sure you have either switch fabric module or a sup720 which has it one inbuilt otherwise you will only be able to connect to the bus at slower transfer rates.

Also be wary on the placement of the 6748 within the 6513 chassis as only 9 -13 have the dual 20 gig fabric connections

Jon Marshall Tue, 02/10/2009 - 12:54


Just to clarify.

The WS-X6148A-GE-TX is not fabric enabled. It doesn't connect at 8Gbps to the switch fabric it connects to the 32Gbps shared bus only (shared being shared between all classic cards). It does support PoE.

The WS-X6748-GE-TX is not fabric enabled, it is fabric only. So it will only work with the Supervisor 720, it cannot connect to the shared bus. If you have a supervisor 2 with a SFM (Switch Fabric Module) it won't work. If you have a Sup32 it won't work. So be aware that this module is useless to you unless you go with Sup720.

They are for entirely different purposes. 6748-GE-TX primarily for servers etc. with high throughput. It supports 2 X 20Gbps connections to the switch fabric which is 40Gbps and you have 48 10/100/1000 ports so there is only slight oversubscription.

The WS-X6148-GE-TX is designed for end user devices etc. where a certain amount of oversubscription is perfectly acceptable.


adamclarkuk_2 Tue, 02/10/2009 - 13:27

Sorry for the mis info there Jon is right the WS-X6748-GE-TX is a CEF7230 line card so will only work with SUP720.

stephen.stack Tue, 02/10/2009 - 13:29

Hi guys,

Thanks again for info. So if i get this right, i get 32Gbps shared on the backplane - against any or all cards installed??? At the moment, my Cat6509 has a sup720 and an existing WS-X6748-GE-TX. A 'show fabric status' shows cards running at 20Gbps.

sh fabric status

slot channel speed module fabric

status status

1 0 20G OK OK

1 1 20G OK OK

5 0 20G OK OK

So.. i guess i'm a but confused.

148 or 748?

We have relativly low bandwitdh usage customers connected to our switch. All port do not really exceed 20Mbps with a couple of expections at out of peak times. I do not expect major growth in the coming years (famous last words eh!!).

I am now leaning towards the WS-X6148A-GE-TX.


Jon Marshall Tue, 02/10/2009 - 13:38


You get 32Gbps shared for all classic line cards with a Sup720. Your existing WS-X6748-GE-TX is not using the shared bus so nothing is using that shared bus at the moment.

Without wishing to overload you with info if you use entirely fabric enabled/fabric only cards in a 6500 with sup720 then you can use compact switching mode. If you add a non-fabric enabled line card you then have to revert to truncated mode. Truncated mode is not as efficient as compact mode. So just by adding a WS-X6148A-GE-TX you are potentially impacting the performance of the switch.

I say potentially because you may not need that sort of performance from your 6500. Do you need PoE because if you don't you may want to consider other modules.

So the WS-X6148A-GE-TX card will be the first to use the 32Gbps so you should be fine.

As i said before, they really are designed for completely separate types of connectivity so it should be failry straightforward as to what you need to choose in terms of these 2 modules.


Joseph W. Doherty Tue, 02/10/2009 - 19:46

Besides the other posters noting the different card chassis connections (shared bus vs. fabric), another important difference is the 6748 supports DFC, the 6148A doesn't (also noted in Rob's post). The DFC supports forwarding on the card itself. Since even the sup720 only supports 15 or 30 Mpps per chassis (about 10 to 20 Gbps for 64 byte packets), 48 gig ports, per card, can quickly exhaust the supervisor's PPS capacity if the ports are pushed to their capacity.

There are other difference between the cards. More information can be found here: http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_data_sheet0900aecd8017376e.html


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