[CentOS] trouble shooting slow ssh logins

aurfalien at gmail.com aurfalien at gmail.com
Thu Jan 21 21:03:01 UTC 2010

> ----- Original Message ----
>> From: "aurfalien at gmail.com" <aurfalien at gmail.com>
>> To: CentOS mailing list <centos at centos.org>
>> Sent: Thu, 21 January, 2010 20:07:27
>> Subject: Re: [CentOS] trouble shooting slow ssh logins
>>> aurfalien at gmail.com wrote:
>>>> Hi all,
>>>> I noticed that my ssh logins to a particular server were taking  
>>>> up to
>>>> 5 seconds to finally login.
>>> This is frequently a DNS issue, is forward+reverse DNS functional?
>> DNS was normal, forward reverse lookups exist and match that host.
> Is the server able to to reverse lookups on the IP address of the  
> incoming client?
> A day or two ago post a suggestion to use UseDNS No in the sshd  
> config file (from memory), which worked for me.
> HTH.

The DNS server also behaved regarding name/ip addy lookups.

This server is a Zimbra mail server which during install, checks for  
proper DNS configs.  I usually check proper functioning DNS by hand  

The ipv6 line was strange but I read a while back, some tech note  
about ensuring that is your last line in hosts.

- aurf

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