I'm trying to import my perfectly good SSL certificate with private key so I can use HTTPS remote management.

I get...

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Imported Certificate too big. Try again!!!!!!!!!!

Any ideas?

Crap... Just found this on another post.

I've had a bit of a tough time this weekend with X.509 certificates. Vigor routers don't seem to handle anything other than certificates which use SHA1 and 1024-bit keys.

That's rubbish. SHA1 is not deemed as secure anymore. My SSL is SHA2 with 2048 key.

That was me.

It looks like 2860s support 2048 bit keys. Not sure if they support any superior ciphers.

Upgrade to the latest firmware, use the in-built function to generate a Root CA, and then you can look at the certificate produced and try and make one in your third-party certificate generator.