尝试SSH到系统时的延迟
问题描述：
当我尝试从我的系统ssh到朋友的系统时，我面临约5-6秒的延迟。这里是命令的详细输出：尝试SSH到系统时的延迟
[email protected]:~$ ssh -v [email protected]
OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 192.168.40.211 [192.168.40.211] port 22.
debug1: Connection established.
debug1: identity file /home/zeus/.ssh/identity type -1
debug1: identity file /home/zeus/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/zeus/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.0p1 Debian-3ubuntu1
debug1: match: OpenSSH_6.0p1 Debian-3ubuntu1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '192.168.40.211' is known and matches the RSA host key.
debug1: Found key in /home/zeus/.ssh/known_hosts:71
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
<---- delay 4-5 seconds------>
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Trying private key: /home/zeus/.ssh/identity
debug1: Offering public key: /home/zeus/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /home/zeus/.ssh/id_dsa
debug1: Next authentication method: password
有人可以帮我弄清楚如何我可以摆脱这种延迟？
答
正如评论中所建议的那样，这可能是一个DNS问题。有占地约步骤来尝试，在这里解决这个文章： http://www.thegeekstuff.com/2010/07/openssh-slow-at-ssh2_msg_service_accept-received/
给出的建议归结为编辑/etc/sshd_config添加/更改UseDNS no，然后重新启动sshd的。很明显，如果不访问服务器就会很棘手！
还应该指出的是，设置UseDNS到no可能不是长期的最佳解决方案。有可能更好地解决相关机器上的DNS问题，如果有的话。
答
我的问题似乎这里有一个答案：
https://superuser.com/a/654153/152271
看来，远程主机尝试做了nslookup来我的主机名（连接一个）。在远程主机中编辑/ etc/hosts并添加我的IP /主机名后，它修复了延迟。
一个常见的DNS问题。请参阅http://superuser.com/questions/372238和http://sysadvent.blogspot.nl/2010/12/day-8-everything-is-dns-problem.html –
，这很有帮助。谢谢。 –