解决方法：

1、在ssh服务端上更改/etc/ssh/sshd_config文件中的配置为如下内容：

1. UseDNS no
2. # GSSAPI options
3. GSSAPIAuthentication no

然后，执行/etc/init.d/sshd restart重启sshd进程使上述配置生效，在连接一般就不慢了。

2、如果还慢的话，检查ssh服务端上/etc/hosts文件中，127.0.0.1对应的主机名是否和 uname -n的结果一样，或者把本机ip和hostname(uname -n结果)加入到/etc/hosts里。

1. [root@C64 ~]# uname -n
2. C64
3. [root@C64 ~]# cat /etc/hosts
4. #modi by oldboy 11:12 2013/9/24
5. 127.0.0.1 C64 localhost localhost.localdomain localhost4 localhost4.localdomain4
6. ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
7. 10.0.0.18 C64
8. ################

利用ssh -v的调试功能查找慢的原因

其实可以用下面的命令调试为什么慢的细节（学习这个思路很重要）。

1. [root@C64 ~]# ssh -v root@10.0.0.19
2. OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
3. debug1: Reading configuration data /etc/ssh/ssh_config
4. debug1: Applying options for *
5. debug1: Connecting to 10.0.0.19 [10.0.0.19] port 22.
6. debug1: Connection established.
7. debug1: permanently_set_uid: 0/0
8. debug1: identity file /root/.ssh/identity type -1
9. debug1: identity file /root/.ssh/id_rsa type -1
10. debug1: identity file /root/.ssh/id_dsa type -1
11. debug1: Remote protocol version 2.0, remote software version OpenSSH_4.3
12. debug1: match: OpenSSH_4.3 pat OpenSSH_4*
13. debug1: Enabling compatibility mode for protocol 2.0
14. debug1: Local version string SSH-2.0-OpenSSH_5.3
15. debug1: SSH2_MSG_KEXINIT sent
16. debug1: SSH2_MSG_KEXINIT received
17. debug1: kex: server->client aes128-ctr hmac-md5 none
18. debug1: kex: client->server aes128-ctr hmac-md5 none
19. debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
20. debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
21. debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
22. debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
23. The authenticity of host '10.0.0.19 (10.0.0.19)' can't be established.
24. RSA key fingerprint is ca:18:42:76:0e:5a:1c:7d:ef:fc:24:75:80:11:ad:f9.
25. Are you sure you want to continue connecting (yes/no)? yes
26. =======>老男孩老师评：这里就是提示保存密钥的交互提示。
27. Warning: Permanently added '10.0.0.19' (RSA) to the list of known hosts.
28. debug1: ssh_rsa_verify: signature correct
29. debug1: SSH2_MSG_NEWKEYS sent
30. debug1: expecting SSH2_MSG_NEWKEYS
31. debug1: SSH2_MSG_NEWKEYS received
32. debug1: SSH2_MSG_SERVICE_REQUEST sent
33. debug1: SSH2_MSG_SERVICE_ACCEPT received
34. debug1: Authentications that can continue: publickey,password
35. debug1: Next authentication method: publickey
36. debug1: Trying private key: /root/.ssh/identity
37. debug1: Trying private key: /root/.ssh/id_rsa
38. debug1: Trying private key: /root/.ssh/id_dsa
39. debug1: Next authentication method: password
40. root@10.0.0.19's password:
41. =======>老男孩老师评：这里就是提示输入密码的交互提示。
42. debug1: Authentication succeeded (password).
43. debug1: channel 0: new [client-session]
44. debug1: Entering interactive session.
45. debug1: Sending environment.
46. debug1: Sending env LANG = en_US.UTF-8
47. Last login: Tue Sep 24 10:30:02 2013 from 10.0.0.18

在远程连接时如果慢就可以确定卡在哪了。

1. [root@C64_A ~]# ssh -v oldboy@10.0.0.17
2. OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
3. debug1: Reading configuration data /etc/ssh/ssh_config
4. debug1: Applying options for *
5. debug1: Connecting to 10.0.0.17 [10.0.0.17] port 22.
6. debug1: Connection established.
7. debug1: permanently_set_uid: 0/0
8. debug1: identity file /root/.ssh/identity type -1
9. debug1: identity file /root/.ssh/id_rsa type -1
10. debug1: identity file /root/.ssh/id_dsa type 2
11. debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
12. debug1: match: OpenSSH_5.3 pat OpenSSH*
13. debug1: Enabling compatibility mode for protocol 2.0
14. debug1: Local version string SSH-2.0-OpenSSH_5.3
15. debug1: SSH2_MSG_KEXINIT sent
16. debug1: SSH2_MSG_KEXINIT received
17. debug1: kex: server->client aes128-ctr hmac-md5 none
18. debug1: kex: client->server aes128-ctr hmac-md5 none
19. debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
20. debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
21. debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
22. debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
23. debug1: Host '10.0.0.17' is known and matches the RSA host key.
24. debug1: Found key in /root/.ssh/known_hosts:2
25. debug1: ssh_rsa_verify: signature correct
26. debug1: SSH2_MSG_NEWKEYS sent
27. debug1: expecting SSH2_MSG_NEWKEYS
28. debug1: SSH2_MSG_NEWKEYS received
29. debug1: SSH2_MSG_SERVICE_REQUEST sent
30. debug1: SSH2_MSG_SERVICE_ACCEPT received
31. debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
32. debug1: Next authentication method: gssapi-keyex
33. debug1: No valid Key exchange context
34. debug1: Next authentication method: gssapi-with-mic

上述配置没配就发现卡到gssapi这。就大概知道是gssapi的问题。

实际上在linux系统优化部分就应该优化SSH服务的此处。