slow ssh connections on LAN

[mshields at namemedia.com (Matt Shields)]

If it's a private lan and you do not have DNS entries for your private
IPs, it's possible that scp/ssh is trying to do a reverse DNS lookup
each time you log in.  You could try setting /etc/ssh/sshd_config on the
server to

UseDNS no

Also, if you want to see debug messages, try adding the "-v" flag for
ssh or scp.  And if you're using pro-sumer products like Linksys or
Netgear, especially consumer/pro-sumer grade Gig-E, don't ever expect
gigabit speeds.  Another thing is ssh/scp adds a layer of encryption to
your transfer, so that slows down your copy.  If you want something
faster, try nfs, ftp, rsync, or anything that's unencrypted.  As long as
you are behind your firewall, any of these should be fine.

Matthew Shields
Sr Systems Administrator
NameMedia, Inc.
(P) 781-839-2828
mshields at namemedia.com
http://www.namemedia.com

-----Original Message-----
From: discuss-bounces at blu.org on behalf of Robert La Ferla
Sent: Sun 7/9/2006 11:16 PM
To: BLU Discussion List
Subject: slow ssh connections on LAN
 
I have a LAN with two Gigabit switches (Linksys + Netgear) with at  
least CAT-5 cabling (maybe 5e but not CAT 6.)  Transfers using "scp"  
between two Linux hosts average 3.9MB/s.  All NICs are 100BT except  
for one Gigabit NIC so I should not expect Gigabit speeds but I do  
expect 100BT speeds.   I have also noticed that "ssh" logins usually  
take a long time (10-15 seconds).  What could be the problem?  How  
should I go about diagnosing it?  What tools should I use?  The LAN  
has a mix of Linux, Mac, Windows and VOIP systems.

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