Cisco Juniper SSH – Cisco Can’t Connect to Juniper Device via SSH – Invalid Modulus Length

ciscojuniperssh

I'm trying to connect from a Cisco 886VA to a Juniper EX2200 via SSH. The connection fails with the following messages on the Cisco:

*Jan 17 09:51:20.823: SSH2 CLIENT 0: Server has chosen 2056 -bit dh keys
*Jan 17 09:51:20.823: %SSH-3-INV_MOD: Invalid modulus length

Is there any way to make this work by changing some parameter on either the Juniper or Cisco device?

IOS Version: 15.2(4)M5

JunOS Version: 12.3R3.4

This is definitely an issue with your DH key size.

Try this:

cisco886va(config)#ip ssh dh min size 4096