ssh localhost工作，但ssh [localhost的外部url]没有

我正在尝试研究如何在工作中使用ssh（它使用OpenSSH 5.3运行基于RHEL的发行版）。我已经获得了关于如何设置密钥，权限等的说明，这些说明在过去显然有效，而且我已经遵循了这封信，但是我无法让ssh工作（如果不明显，我对ssh完全不熟悉）。

让我感到困惑的是，从机器本身来看，ssh localhost并且ssh 127.0.0.1完美地工作，但ssh [url of machine]不是：-v给出输出

OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to <url> [::1] port 22.
debug1: Connection established.
debug1: identity file /home/<username>/.ssh/identity type -1
debug1: identity file /home/<username>/.ssh/id_rsa type -1
debug1: identity file /home/<username>/.ssh/id_dsa type 2
ssh_exchange_identification: Connection closed by remote host

这与我尝试远程登录时输出的输出相同。我没有管理员权限，所以我认为我无法获得任何日志。

这是否能给任何人提供任何关于问题的线索，或者有没有办法在没有root访问权限的情况下获得有关失败的更多细节？

编辑：我无法进入/etc/ssh/sshd_config，但/etc/ssh/ssh_config包含：

#   $OpenBSD: ssh_config,v 1.25 2009/02/17 01:28:32 djm Exp $

# This is the ssh client system-wide configuration file.  See
# ssh_config(5) for more information.  This file provides defaults for
# users, and the values can be changed in per-user configuration files
# or on the command line.

# Configuration data is parsed as follows:
#  1. command line options
#  2. user-specific file
#  3. system-wide file
# Any configuration value is only changed the first time it is set.
# Thus, host-specific definitions should be at the beginning of the
# configuration file, and defaults at the end.

# Site-wide defaults for some commonly used options.  For a comprehensive
# list of available options, their meanings and defaults, please see the
# ssh_config(5) man page.

# Host *
#   ForwardAgent no
#   ForwardX11 no
#   RhostsRSAAuthentication no
#   RSAAuthentication yes
#   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   GSSAPIKeyExchange no
#   GSSAPITrustDNS no
#   BatchMode no
#   CheckHostIP yes
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
#   IdentityFile ~/.ssh/identity
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   Port 22
#   Protocol 2,1
#   Cipher 3des
#   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
#   MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160
#   EscapeChar ~
#   Tunnel no
#   TunnelDevice any:any
#   PermitLocalCommand no
#   VisualHostKey no
Host *
    GSSAPIAuthentication yes
# If this option is set to yes then remote X11 clients will have full access
# to the original X11 display. As virtually no X11 client supports the untrusted
# mode correctly we set this to yes.
    ForwardX11Trusted yes
# Send locale-related environment variables
    SendEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES 
    SendEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT 
    SendEnv LC_IDENTIFICATION LC_ALL LANGUAGE
    SendEnv XMODIFIERS

看看/etc/ssh/sshd_config。（如果你可以的话...）

配置的东西定义了SSH服务器的行为，如接受连接以及如何进行授权。