How to increase SCP file transfer speed for Cisco IOS Routers (newer and older firmware)

As you likely already know, you can copy files to a cisco router from any host using SCP, it's as easy as using ssh!

What you may have noticed however is the very slow file transfer speeds when copying to most Cisco Devices. There is however some configuration changes you can make on the router that will increase the copying speed significantly.

 For routers running IOS XE 17.2.1 and onwards, you can use the "ip ssh bulk-mode" config command as per the example below:

router#config t
Enter configuration commands, one per line.  End with CNTL/Z.
router(config)#ip ssh bulk-mode ?
  <131072-1073741824>  SSH window-size
  <cr>                 <cr>
router(config)#ip ssh bulk-mode

For routers running IOS XE 16.6.1 or higher, a similar command also exists, but needs to be configured with the additional ip tcp window-size command, and the values between these two commands must match, as per the example below:

router(config)#ip ssh window-size ?

  <8192-131072>  SSH window-size in bits 

router(config)#ip ssh window-size 10000

%% Warning: This cli may have impact on CPU. 

Please configure ip tcp window-size<> with same value,for this CLI to work

router(config)#ip tcp window-size 10000

The commands take effect as soon as you configure them, but don't apply to transfers currently in progress, just kill any current transfer and start it again, trust me! It's going to be at least 10 times faster now to upload.

I hope this helps someone out there!