switching happens first here?

[Saman Shamim]

A quick basic question:

In the following diagram,

• Host H has a Default Gateway of S2.
  
• L3 switch has a routed L3 port to R and has a static route to 192.168.10.X network via R.
  
• L3 swtich receives the blue packet.
  

Question: How does L3 SW handle this? Does it look at the "Frame" and send the traffic to S2 without stripping off the "Packet"?

Click on the picture to enlarge.

[Joseph W. Doherty · Accepted solution]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

A L3 switch should first act as a L2 switch, i.e. it will forward the L2 frame to the destination MAC.  S2, will write a new frame likely with a destination of L3 SW, as you show a L3 link between R and L3 SW.

If H's DG was L3 SW, then the original destination MAC would be L3 SW's.

It's also possible in the original instance, S2 would send a redirect message back to H.