When switch is reloaded, the crypto keys disappear even though the write memory command is issued before every reload.
After you configure the Sup720 for Secure Shell (SSH), SSH works. But after a reload, SSH no longer works. This occurs because the Rivest, Shamir, and Adelman (RSA) key is on longer in there. When the RSA key is regenerated, the SSH works again.
This problem is documented in Cisco bug ID CSCeb54694.
Complete these steps for a workaround:
Generate the RSA key everytime after reload. In order to generate RSA key pairs, use the crypto key generate rsacommandinglobal configuration mode.
This problem is resolved in Cisco IOS 12.2(17b)SXA and later, which can be downloaded from Cisco Downloads.