OEL 6.3 :Slow login due to /etc/ssh/sshd_config configuration

UNIX for Advanced & Expert Users
1

Version: Oracle Enterprise Linux 6.3
Running on VMWare Workstation

When I login to my Linux VM from putty, the third line prompting for password comes only after few seconds.

login as: root
Access denied
root@192.168.0.235's password: ---> It takes around 5 seconds to get this prompt

I managed to fix this issue after several trial and error experiments.
I have to do both Step1 and Step2 mentioned below to fix this issue. Doing either one of Step1 and Step2 won't fix the issue

Step1.
In

/etc/ssh/sshd_config file

Comment the line

GSSAPIAuthentication yes

and
Remove the comment for the line

 GSSAPIAuthentication no

sshd_config file should look like below

grep GSSAPI /etc/ssh/sshd_config
# GSSAPI options
GSSAPIAuthentication no
#GSSAPIAuthentication yes
#GSSAPICleanupCredentials yes
GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no

Step2. In /etc/ssh/sshd_config file
I commented the line

UseDNS yes

and then
uncommented

UseDNS no

and did a restart using

/etc/init.d/sshd restart

Soon, I'll have to use DNS functionality for this VM. So, I am worried that the above change ("UseDNS no") will prevent the VM from using the DNS service.
Is there any other workaround to make the login quick?

2

It is fine to set UseDNS to no. UseDNS is only necessary if you use hostname-based authentication (which is very weak authentication)

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