Exception caught in Spectrum NCM: Algorithm negotiation fail

Products

• Spectrum
• Network Observability

Issue/Introduction

When attempting to backup the running configuration of an Oracle AcmePacketDV device via NCM using SSH, it fails with the following errors:

SPC-OCC-10747: Error capturing configuration for host:
SPC-OCC-11549: Capture failed.

Utilising KB SPC-OCC-10747 and SPC-OCC-11549 error for custom NCM SSH device family (broadcom.com) to review the error, enabling debug to MAX in NCM config.xml, the following error is shown in NCMSERV.OUT log:

com.aprisma.spectrum.scmd.ScmService.endConfig

    com.jcraft.jsch.JSchException: Algorithm negotiation fail

Environment

DX NetOps Spectrum release : 20.2 or later

Cause

In this particular case, the device supports only the diffie-hellman-group14-sha256 algorithm.

This algorithm is not supported by the JSCH library utilised by Spectrum.

Resolution

The JSCH library supports the following algorithms.

ecdh-sha2-nistp256
ecdh-sha2-nistp384
ecdh-sha2-nistp521
diffie-hellman-group14-sha1
diffie-hellman-group-exchange-sha256
diffie-hellman-group-exchange-sha1
diffie-hellman-group1-sha1

So you will need to enable one of the above algorithms that is supported by the JSCH library on the device.

Additional Information

For reference, here is the command information from Oracle for the devices: Configuration Information (oracle.com)