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Can I do layer 2 switching between different switching modules in a router or it only works withing the same switching module ??

Hello All

     Appreciate if you help me with below

When I have more than Ethernet switching module into a router, do layer 2 switching works between these swithcing modules or it only works withing the same switching module ??

Imagine I have two WS-X6748-SFP switching modules inserted inserted in slots 1 and 2 at a 7600 router as shown in figure

All PCs (R1, R6 ,R5 and R7) are in same access vlan

Will connectivity works between hosts on different switching modules ??


I tried it on GNS3 using 3725 router with intergrated switching module NM-16ESW and below are the results

- I was able to ping to between hosts on same switching modules

- Not able to ping between hosts on different swithcing modules

- Not able to ping from any host to SVI configured at switch !!

Does this makes sense ??


Hall of Fame Expert

Hi Sherif,

It sure does work.  You can have for example a 7609 fully loaded all with X6748 modules and put one PC in each module in the same VLAN.




Hello Reza

Thanks for your reply

So generally switching modules communicate normally together and this is not a specific feature for 7600 i.e. same applies to other router chasssis as 3800 or any other chassis , correct ?

Maybe GNS3 hanged or something

Another question plz

Can I change a layer port in normal layer 3 module as SPA-2X1GE-V2 to a layer 2 port and put in access mode

In this case, it will communicate normally with switching module, correct ?

Many thanks

Hall of Fame Cisco Employee


For switching modules installed into ISR (x600 series, x800 series, x900 series) routers, the communication between individual switching modules or HWICs is different. Their switching backplane does not extend through the router chassis, as opposed to high end switches/routers (6500, 7600, ...). Instead, you have to connect these switching cards by an external cable, and configure the interconnecting ports as stacking partners. Only then the intrachassis switching between the individual cards will take place.

Read this document for more information:

Best regards,



That what I was looking for ... Thx Peter

Now kindly answer below 2 questions

Can I change a normal layer 3 port in a module as SPA-2X1GE-V2 for high end switches/routers to a layer 2 port and put it in access mode.  In this case, will it communicate normally with switching module as WS-X6748-SFP  ?

2nd belongs to below URL

Many many thanks

Sherif Ismail

Hall of Fame Cisco Employee

Hello Sherif,

Regarding the SPA-2X1GE-V2, L2 support always strongly depends on the particular type of the card. Some cards do support switching, some do not - sadly, I am not familiar with these high-end cards and I cannot give any exact guidance. If you have such a card available, do you have the switchport command available on a particular port of that SPA? If yes then it seems the card should support switched operation.

If somebody could share his/her knowledge here I would appreciate that very much as well!

Regarding the PVST+/MST thread - I will answer during the next few hours.

Best regards,




To my knowledge the SPA card is a L3 card only ie. you cannot make it a L2 switchport. However there is a simple solution to this. Just try configuring "switchport" under the interface and see what happens ?



Thanks Jon/Peter

If it supports L2 switching, It will communicate normally with other L2 ports whether SPA or switching module, same slot or not , thanks to backplane of highend routers as 7600 , correct ?


If it did support L2, which i doubt, then yes it would. All modules/linecards can communicate with each via the switch fabric or shared bus on a 7600.



Many thanks Jon

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