SSH 登录期间的随机延迟

Question

当我尝试从我的 MacBook Air (10.6) 登录远程 linux (ubuntu) 机器时，每次在我获得密码之前都会延迟大约 4-5 秒。Verbose 产生以下结果：

:~ ssh -v username@IPADDRESS

OpenSSH_5.2p1, OpenSSL 0.9.8r 8 Feb 2011
debug1: Reading configuration data /etc/ssh_config
debug1: Applying options for *
debug1: Connecting to 18.78.4.61 [18.78.4.61] port 22.
debug1: Connection established.
debug1: identity file /Users/Fabrice/.ssh/identity type -1
debug1: identity file /Users/Fabrice/.ssh/id_rsa type -1
debug1: identity file /Users/Fabrice/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.8p1 Debian-1ubuntu3
debug1: match: OpenSSH_5.8p1 Debian-1ubuntu3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.2
debug1: Unspecified GSS failure.  Minor code may provide more information
No credentials cache found

debug1: Unspecified GSS failure.  Minor code may provide more information
No credentials cache found

debug1: Unspecified GSS failure.  Minor code may provide more information

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 '18.78.4.61' is known and matches the RSA host key.
debug1: Found key in /Users/Fabrice/.ssh/known_hosts:6
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

**------------------- 4-5 seconds Delay -----------------------**

debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Trying private key: /Users/Fabrice/.ssh/identity
debug1: Trying private key: /Users/Fabrice/.ssh/id_rsa
debug1: Trying private key: /Users/Fabrice/.ssh/id_dsa
debug1: Next authentication method: password

这对我来说似乎很奇怪 - 关于我如何改变它的任何想法？我读了一些关于 DNS 解析可能是罪魁祸首的内容......

谢谢！

Answer 1

这是 Ubuntu 的一个众所周知的问题。您必须通过设置UseDNS为noin来禁用 Ubuntu 服务器上的反向 DNS 查找/etc/ssh/sshd_config。关于这个主题有很多文章，这只是其中之一。