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Groups > comp.os.linux.networking > #4677

Re: Delay when SSH'ing into some systems in my LAN

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On 2020-07-21, S.K.R. de Jong <SKRdJ@nowhere.net> wrote:
> On Tue, 21 Jul 2020 16:28:57 +0000, William Unruh wrote:
>
>> On 2020-07-21, S.K.R. de Jong <SKRdJ@nowhere.net> wrote:
>>> 	This started happening recently, with no apparent reason.
>>>
>>> 	I have systems A, B, C, D in my LAN. When I SSH from A into B the
>>> connection gets established immediately. However when I do it from A to
>>> C I get the following SSH traces in A:
>>>
>>> 	OpenSSH_7.4p1, OpenSSL 1.0.2u  20 Dec 2019 debug1: Reading
>>> 	configuration data /home/xyz/.ssh/config debug1: Reading 
> configuration
>>> 	data /etc/ssh/ssh_config debug2: resolving "C" port 22
>> 
>> Try to ssh into C using C's IP address rather than name.
>> If that goes immediately Try putting C's name into A's /etc/hosts Since
>> it seems to be A that is complaining, try putting C's name and address
>> into /etc/hosts on A.
>
> 	Thanks. When using IP addresses instead, or entering the relevant 
> names into /etc/hosts, the delay disappears.
>
>> It seem's that it is the reverse dns that is problematic.
>
> 	I would agree.
>
>> Note that in the above A,B,C,D could be names or they could be IP
>> addresses. It might help to actually give us the exact log lines, rather
>> than the edited ones.
>
> 	They were meant to be names, not IP addresses.

So you are running an internal dns server? If you have your machines on
fixed addresses, and do not have too many of them, using /etc/hosts is
probably more efficient. If they are using dhcp and the various machine
have constantly fluctuating IP addresses, or you have lots of
machines(lets say>10) then a dns server is probably best and you then
need to figure out why it is not delivering on a dns query. tcpdump on a
third machine on that network would show if the query was actually being
sent out to the dns server, and whether it is returning reasonable
answers of grabage. Also, it would seem that you have a secondary dns
server which is used after the timeout on the first one. I assume it is
also local-- so why is it returning something reasonable and the first
is not. 
>

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Thread

Delay when SSH'ing into some systems in my LAN "S.K.R. de Jong" <SKRdJ@nowhere.net> - 2020-07-21 15:27 +0000
  Re: Delay when SSH'ing into some systems in my LAN William Unruh <unruh@invalid.ca> - 2020-07-21 16:28 +0000
    Re: Delay when SSH'ing into some systems in my LAN "S.K.R. de Jong" <SKRdJ@nowhere.net> - 2020-07-21 18:29 +0000
      Re: Delay when SSH'ing into some systems in my LAN William Unruh <unruh@invalid.ca> - 2020-07-21 19:52 +0000
    Re: Delay when SSH'ing into some systems in my LAN "S.K.R. de Jong" <SKRdJ@nowhere.net> - 2020-07-21 19:33 +0000

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