某天服务器A与B，互相ping没问题，telnet 22端口没问题
ssh -v a@10.80.97.241 OpenSSH_6.6.1, OpenSSL 1.0.1k-fips 8 Jan 2015 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 20: Applying options for * debug1: Connecting to 10.80.97.241 [10.80.97.241] port 22. debug1: Connection established. debug1: identity file /home/zengming/.ssh/id_rsa type -1 debug1: identity file /home/zengming/.ssh/id_rsa-cert type -1 debug1: identity file /home/zengming/.ssh/id_dsa type -1 debug1: identity file /home/zengming/.ssh/id_dsa-cert type -1 debug1: identity file /home/zengming/.ssh/id_ecdsa type -1 debug1: identity file /home/zengming/.ssh/id_ecdsa-cert type -1 debug1: identity file /home/zengming/.ssh/id_ed25519 type -1 debug1: identity file /home/zengming/.ssh/id_ed25519-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.6.1 debug1: Remote protocol version 2.0, remote software version OpenSSH_6.4 debug1: match: OpenSSH_6.4 pat OpenSSH* compat 0x04000000 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5-etm@openssh.com none debug1: kex: client->server aes128-ctr hmac-md5-etm@openssh.com none debug1: sending SSH2_MSG_KEX_ECDH_INIT debug1: expecting SSH2_MSG_KEX_ECDH_REPLY Connection closed by 10.80.97.241
后面在本机上修改了mtu为1500以下就好了：
sudo ifconfig enp0s25 mtu 1200 #临时修改