参考：https://developer.aliyun.com/article/1479077 （ECC详解）
https://www.cnblogs.com/nexiyi/archive/2013/01/06/2847865.html （RSA、DSA和ECC比较）
默认配置IP、aaa和user-interface后无法远程登录
SecureCRT连接提示“Key exchange failed.
No compatible hostkey. The server supports these methods: rsa_sha2_512,rsa_sha2_256”
原来交换机只配置了ssh server publickey rsa_sha2_256 rsa_sha2_512和CRT不兼容
增加ecc公钥算法即可远程连接
