converting routed port to L2

[joelm]

I have an ISR4451 router (running version 16.8.1) with an SM-X-ES3D-48-P card in it, which is a card version of the C3560E switch (running version 15.2(3)E1).  Several of the hosts on the switch are serving NTP traffic, which are 60-100 byte UDP packets, for the public NTP pool. I can adjust the number of NTP clients I accept and with my current configuration, the NTP traffic is a steady 1-2Mbps.  The router is keeping up just fine, but the switch module is being hammered.

router#show process cpu
CPU utilization for five seconds: 1%/0%; one minute: 0%; five minutes: 0%

switch1#show processes cpu 
CPU utilization for five seconds: 64%/0%; one minute: 64%; five minutes: 64%

The router uses one of the 4 interfaces as the inbound interface from the internet.  Since there are three spare interfaces on the router, I was thinking I could move the NTP hosts onto those interfaces so that traffic doesn't have to go through the switch.  In order to do this, I think I need to turn these three routed ports into switch ports, but switchport isn't a valid command to convert them:

router(config)#int gi0/0/3
router(config-if)#s?
service        service-insertion  service-policy  service-routing
shutdown       snapshot           snmp            source
spanning-tree  speed              standby         subscriber

If I can solve this, I can offer more service to the NTP pool.

Seems like I'm missing something fundamentally simple.  Can someone offer me suggestions/documentation?

[Deepak Kumar]

Hi,

I didn't work on this module but interface naming looks like that you are trying to convert onboard interface in Layer2. This router is having a layer 3 interfaces. You can use SM-X-ES3D-48-P card's interface as layer 2. 

Can you share the "Show IP interface brief" output? Also share a full output of "switch1#show processes cpu" output.

[balaji.bandi]

I do not believe onboard ports can act as L2 (these are routed ports ), by saying that you have other option you make  Bridge interface - if this option works for you.

[joelm · Accepted solution]

Turns out the real answer to the high CPU utilization on the switch is is a known bug in my version of IOS.

Blinky lights are great for movies; sometimes not so good for computers.

[Joseph W. Doherty]

Ah, nice to see you found the cause of your problem!

BTW, the "speed" of your on-board L3 switch module should be way, way above the performance of your 4451 unless the switch module is processing on its main CPU (which normally, it shouldn't be doing much of - especially if it's doing L2 forwarding).