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WS-X6148-GE-TX - Port speed limitation Question

Level 2
Level 2

Hello Cisco Team,

I have a question  about the mapping of the:

WS-X6148A-GE-TX: 1-8, 9-16, 17-24, 25-32, 33-40, 41-48
Is there a speed limit of 1 G L3 per 1ports 1-8 and 9-16?
i need more info to make sure i can run it as L3.
I had a look here but need a confirm :
5 Replies 5

Hall of Fame
Hall of Fame

Not that I am aware of any Limitations.

Is there a speed limit of 1 G L3 per 1ports 1-8 and 9-16?   not sure what you mean by speed Limit. - each port you should get 1GB ( depends  on the backplane and Sup card you have)

depends on the code. refer config guide if any Limitation is mentioned.


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*Number of ports: 48
Number of port groups: 6
Port ranges per port group: 1-8, 9-16, 17-24, 25-32, 33-40, 41-48 *The
aggregate bandwidth of each port group is 1 Gbps.

*Number of ports: 48
Number of port groups: 2
Port ranges per port group: 1-24, 25-48
Note WS-X6148-GE-TX, WS-X6148V-GE-TX, and WS-X6148-GE-45AF do not
support these features:
*More than 1 Gbps of traffic per EtherChannel

Can anyone comment on this ? Does this mean we can get a max of 6 Gig
throughput on a 6148A card and max 2 Gbit on a 6148 ?
Or do these 
numbers only apply to etherchannels ?
Or do these numbers only apply to Eigrp L3 load balancing ? ?

I didn't see this posting until after my prior posting, and yes, it confirms each port group is limited to a gig.  (Actually I thought that too might be the case, but wasn't sure, so my prior posting didn't address the actual bandwidth limitation.  This reference further documents this in one of its restriction sections, see below.)


The WS-X6148A-GE-TX switching module has 48 oversubscribed ports in six groups of eight ports each:

Ports 1, 2, 3, 4, 5, 6, 7, 8

Ports 9, 10, 11, 12, 13, 14, 15, 16

Ports 17, 18, 19, 20, 21, 22, 23, 24

Ports 25, 26, 27, 28, 29, 30, 31, 32

Ports 33, 34, 35, 36, 37, 38, 39, 40

Ports 41, 42, 43, 44, 45, 46, 47, 48

The eight ports within each group use common circuitry that effectively multiplexes the group into a single, nonblocking, full-duplex Gigabit Ethernet connection to the internal switch fabric. For each group of eight ports, the frames that are received are buffered and sent to the common Gigabit Ethernet link to the internal switch fabric. If the amount of data received for a port begins to exceed buffer capacity, flow control sends pause frames to the remote port to temporarily stop traffic and prevent frame loss.

If the frames received on any group exceeds the bandwidth of 1 Gbps, the device starts to drop the frames. These drops are not obvious as they are dropped at the internal ASIC rather than the actual interfaces. This can lead to slow throughput of packets across the device

If more throughput is required, either use ports from a line module that does not use oversubscription or use ports from different port-groupings on oversubscribed line modules. For example, if the line module has 48 ports in groups of eight, you can select ports 1, 9, 17, 25, 33, and 41 for the same port channel.

Cisco recommends that you use 61xx, 63xx, and 64xx modules for access layer as they are usually oversubscribed and always have only a bus connection to the backplane switching bus. For a backbone connection, it is recommended that you use 65xx or 67xx modules which always have either an eight or 20 GB dedicated connection to the switch fabric.


BTW, direct answers to your other questions:

6 Mbps max for 6148A?  Yes, correct.  Also applies regardless whether Etherchannel, L3 routing LB, etc.

Can all 6148A ports be routed ports?  I believe so.


Joseph W. Doherty
Hall of Fame
Hall of Fame

I recall a port group, such as 1-8 on the 6148A, is controlled by a single ASIC, and yes, there might be a bandwidth limitation for that group, less than the all the ports, in that group, provide.  Don't recall whether it's always 1 Gbps, though.  (I also recall [?], ports within the same port group might be wire rate between themselves (within the same port group).

However, also keep in mind with the 6148A you have 48 gig ports, but this is a shared bus only line card, which is limited to 16 Gbps (duplex [NB: why it's often referred to as having 32 Gbps]) for the whole chassis.

Further, unless you use DFC line cards, shared bus line cards, all use the sup for forwarding, which may only provide them about 15 Mpps, again shared across the whole chassis.  (NB: 15 Mpps is good for about 10 Gbps, non-duplex, for 64 byte packets.)

The 6148A has other limitations too.  The card is "marketed" for user hosts that aren't going to use gig, continuously.  I.e. generally a bad design choice for server hosts.

(BTW, until you get up to the sup2T, even CEF720 fabric cards only provide 40 Gbps, i.e. e.g. 6748 line card has insufficient bandwidth to/from the fabric for all 48 gig ports.)

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