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EtherSwitch module for UCS Express

Level 1
Level 1

Dear all,

On CCO, i see this note:-

"The EtherSwitch modules are not required for Cisco UCS Express, however they simplify configuration and improve performance."

Can someone please kindly explain to me in terms of using UCS Express on an ISRG2, what's the adv & disadv of using the EtherSwitch module or not.

Would greatly appreciated if anyone can shed some lights on this.



3 Replies 3

Benjamin Kools
Level 1
Level 1


The multi gigabit fabric (MGF) on the new ISR G2's connects only insertable modules into it, such as SMs, EHWICs, PVDMs, etc. The front panel ports on an ISR do not connect directly to the MGF, rather they connect through the CPU which then connects into the MGF. If a host which connects to Gig0/0 for instance wants to access data on the UCS Express SRE module, it would need to go through the CPU to reach it, thus causing an impact on the router's performance. An EtherSwitch module however connects directly to the MGF so traffic can route from it to the SRE module with no impact to the router.

The below link shows the various configuration options for the UCS Express Networking:

Hope this helps!



Thanks so much for your explanation.  I only have 1 question regarding the various configuration options for UCS Express:-

On page 3-25, it has an option called "External Interface Configuration". 

But  what is the "External Interface"?? Is it the built-in ports on the ISR  G2 (e.g. gi 0/0)?? Or if it is the EtherSwitch ports, how is it different from the  recommended configuration option of the MGF Layer 2 Switch Configuration on p3-4?



Hello Hunt,

For UCS-Express support, please post your questions here: .  To log into the site you'll need a Cisco Care Online (CCO) ID, which you can create free of charge  by clicking on the 'Register Now' link.

Regarding your question, the External Interface Configuration refers to the external port located on the SRE module.  This port configured via the vSphere Client, would allow packets to bypass the router as shown in Figure 3-7 in that document. 

Regarding the difference between the External Interface and the MGF Layer 2 Switch Configuration, the switch configuration still utilizes the router for communication, but bypasses cpu utlization which in effect adds less load to the router.  Also EtherSwitches have many ports, and are directly configurable as you know while the External Interface has just one port.



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