Solution to slow centos SSH remote connection

Solution to slow centos SSH remote connection

The primary cause of slow connection is DNS resolution.

Solution:

1. Change the configuration in the/etc/ssh/sshd_config file on the ssh server as follows:
UseDNS no
# GSSAPI options
GSSAPIAuthentication no
Then, run the/etc/init. d/sshd restart command to restart the sshd process to make the above configuration take effect. The connection is generally not slow.

If it is still slow, check whether the host name corresponding to 127.0.0.1 and
The uname-n results are the same, or you can add the local ip address and hostname (uname-n results) to/etc/hosts.

[Python] view plaincopy

1. [Root @ C64 ~] # Uname-n
2. C64
3. [Root @ C64 ~] # Cat/etc/hosts
4. # Modibyoldboy11: 122013/9/24
5. 127.0.0.1C64localhostlocalhost.localdomainlocalhost4localhost4.localdomain4
6. : 1localhostlocalhost. localdomainlocalhost6localhost6. localdomain6
7. 10.0.0.18C64
8. ################

Use the ssh-v debugging function to find the cause of slowness
In fact, you can use the following command to debug the slow details (learning this idea is very important ).

[Python] view plaincopy

1. [Root @ C64 ~] # Ssh-vroot @ IP Address
2. OpenSSH_5.3p1, OpenSSL1.0.0-fips29Mar2010
3. Debug1: Readingconfigurationdata/etc/ssh/ssh_config
4. Debug1: Applyingoptionsfor *
5. Debug1: Connectingto10.0.0.19 [10.0.0.19] port22.
6. Debug1: Connectionestablished.
7. Debug1: permanently_set_uid: 0/0
8. Debug1: identityfile/root/. ssh/identitytype-1
9. Debug1: identityfile/root/. ssh/id_rsatype-1
10. Debug1: identityfile/root/. ssh/id_dsatype-1
11. Debug1: Remoteprotocolversion2.0, remotesoftwareversionOpenSSH_4.3
12. Debug1: match: OpenSSH_4.3patOpenSSH_4 *
13. Debug1: Enablingcompatibilitymodeforprotocol2.0
14. Debug1: LocalversionstringSSH-2.0-OpenSSH_5.3
15. Debug1: SSH2_MSG_KEXINITsent
16. Debug1: SSH2_MSG_KEXINITreceived
17. Debug1: kex: server-> clientaes128-ctrhmac-md5none
18. Debug1: kex: client-> serveraes128-ctrhmac-md5none
19. Debug1: SSH2_MSG_KEX_DH_GEX_REQUEST (1024 <1024) sent
20. Debug1: expectingSSH2_MSG_KEX_DH_GEX_GROUP
21. Debug1: SSH2_MSG_KEX_DH_GEX_INITsent
22. Debug1: expectingSSH2_MSG_KEX_DH_GEX_REPLY
23. Theauthenticityofhost '10. 0.0.19 (10.0.0.19) 'can' tbeestablished.
24. RSAkeyfingerprintisca: 18: 42: 76: 0e: 5a: 1c: 7d: ef: fc: 24: 75: 80: 11: ad: f9.
25. Areyousureyouwanttocontinueconnecting (yes/no )? Yes
26. ======> Here is the interaction prompt for saving the key.
27. Warning: Permanentlyadded '10. 0.0.19 '(RSA) tothelistofknownhosts.
28. Debug1: ssh_rsa_verify: signaturecorrect
29. Debug1: SSH2_MSG_NEWKEYSsent
30. Debug1: expectingSSH2_MSG_NEWKEYS
31. Debug1: SSH2_MSG_NEWKEYSreceived
32. Debug1: SSH2_MSG_SERVICE_REQUESTsent
33. Debug1: SSH2_MSG_SERVICE_ACCEPTreceived
34. Debug1: Authenticationsthatcancontinue: publickey, password
35. Debug1: Nextauthenticationmethod: publickey
36. Debug1: Tryingprivatekey:/root/. ssh/identity
37. Debug1: Tryingprivatekey:/root/. ssh/id_rsa
38. Debug1: Tryingprivatekey:/root/. ssh/id_dsa
39. Debug1: Nextauthenticationmethod: password
40. Root@10.0.0.19 'spassword:
41. <Strong >=====> here is the interaction prompt prompting you to enter the password. </Strong>
42. Debug1: Authenticationsucceeded (password ).
43. Debug1: channel0: new [client-session]
44. Debug1: Enteringinteractivesession.
45. Debug1: Sendingenvironment.
46. Debug1: SendingenvLANG = en_US.UTF-8
47. Lastlogin: TueSep2410: 30: 022013from10. 0.0.18
48. <Strong> If the remote connection is slow, you can determine where the connection is located. </Strong>
49. [Root @ C64_A ~] # Ssh-voldboy @ IP Address
50. OpenSSH_5.3p1, OpenSSL1.0.0-fips29Mar2010
51. Debug1: Readingconfigurationdata/etc/ssh/ssh_config
52. Debug1: Applyingoptionsfor *
53. Debug1: Connectingto10.0.0.17 [10.0.0.17] port22.
54. Debug1: Connectionestablished.
55. Debug1: permanently_set_uid: 0/0
56. Debug1: identityfile/root/. ssh/identitytype-1
57. Debug1: identityfile/root/. ssh/id_rsatype-1
58. Debug1: identityfile/root/. ssh/id_dsatype2
59. Debug1: Remoteprotocolversion2.0, remotesoftwareversionOpenSSH_5.3
60. Debug1: match: OpenSSH_5.3patOpenSSH *
61. Debug1: Enablingcompatibilitymodeforprotocol2.0
62. Debug1: LocalversionstringSSH-2.0-OpenSSH_5.3
63. Debug1: SSH2_MSG_KEXINITsent
64. Debug1: SSH2_MSG_KEXINITreceived
65. Debug1: kex: server-> clientaes128-ctrhmac-md5none
66. Debug1: kex: client-> serveraes128-ctrhmac-md5none
67. Debug1: SSH2_MSG_KEX_DH_GEX_REQUEST (1024 <1024) sent
68. Debug1: expectingSSH2_MSG_KEX_DH_GEX_GROUP
69. Debug1: SSH2_MSG_KEX_DH_GEX_INITsent
70. Debug1: expectingSSH2_MSG_KEX_DH_GEX_REPLY
71. Debug1: Host '10. 0.0.17 'isknownandmatchestheRSAhostkey.
72. Debug1: Foundkeyin/root/. ssh/known_hosts: 2
73. Debug1: ssh_rsa_verify: signaturecorrect
74. Debug1: SSH2_MSG_NEWKEYSsent
75. Debug1: expectingSSH2_MSG_NEWKEYS
76. Debug1: SSH2_MSG_NEWKEYSreceived
77. Debug1: SSH2_MSG_SERVICE_REQUESTsent
78. Debug1: SSH2_MSG_SERVICE_ACCEPTreceived
79. Debug1: Authenticationsthatcancontinue: publickey, gssapi-keyex, gssapi-with-mic, password
80. Debug1: Nextauthenticationmethod: gssapi-keyex
81. Debug1: NovalidKeyexchangecontext
82. Debug1: Nextauthenticationmethod: gssapi-with-mic

If the above configuration is not configured, It is found to be stuck in gssapi. It is probably a problem with gssapi.

In fact, the SSH service should be optimized in the linux system optimization section.