連不上raspbian的ssh - Linux

因工作需求第一次操作linux系統
目前手頭有兩台樹莓派
在同一個網域下
一台可以用ssh連上，一台就沒辦法
這實在讓我不知道該如何解決
用ssh -v看出現以下訊息

OpenSSH_6.6.1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Connecting to 172.20.10.2 [172.20.10.2] port 22.
debug1: Connection established.
debug1: identity file /home/900772/.ssh/id_rsa type -1
debug1: identity file /home/900772/.ssh/id_rsa-cert type -1
debug1: identity file /home/900772/.ssh/id_dsa type -1
debug1: identity file /home/900772/.ssh/id_dsa-cert type -1
debug1: identity file /home/900772/.ssh/id_ecdsa type -1
debug1: identity file /home/900772/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/900772/.ssh/id_ed25519 type -1
debug1: identity file /home/900772/.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_6.7p1 Ras
pbian-5+deb8u3
debug1: match: OpenSSH_6.7p1 Raspbian-5+deb8u3 pat OpenSSH* compat 0x04000000
debug1: SSH2_MSG_KEXINIT sent
Connection closed by 172.20.10.2

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