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New Member

NTP with Authentication on Cisco 2621

I am trying to configure NTP in my network with authentication. I dont have any device in my network with H/W clock. I am planning to set clock manually on cisco 2621 (Acts as master with stratum 4) and enable authentication as well. I configured as below on master (Cisco 2621;host name R1)

r1(config)#ntp master 4

r1(config)#ntp authenticate

r1(config)#ntp authentication-key 1 md5 cisco

r1(config)#ntp trusted key 1

on client switches

r2(cofnig)#ntp authentication-key 1 md5 cisco

r2(config)#ntp server r1 key 1

is this all needed to get what I wanted? or anything is missing? I couldnt succeed with the above.

As an alternative I am planning to consider NTP Access by restricting with an ACL. What keyword should I use to synchronize is it serve-only or serve???

Please help me!!!!!!!



  • Other Network Infrastructure Subjects
New Member

Re: NTP with Authentication on Cisco 2621


Restricting NTP access using ACLs can be accomplished by using the ntp access-group command under router global configuration mode.

Based on your configuration, NTP authentication has not been enabled on the client. Did you try specifying the NTP server's IP address instead of the hostname on the client?

The following link should be useful:

Hope this helps,


New Member

Re: NTP with Authentication on Cisco 2621


Thanks for the response.

Do I have to enable authentication even at client by the command "ntp authenticate"? I dont want peer association.

I tried by giving ip address instead of hostname but in vain.

If I configure ACL what keyword should I use for NTP access. Is it serve-only or serve?

I also wanted to know is there any problem in giving loopback ip as NTP server ip address (Currently I am using loopback as NTP serveru ip add). I knew HSRP virtual IP does not work as NTP server ip.................Is this same with Loopback ip aswell?????

Thanks in advance,


New Member

Re: NTP with Authentication on Cisco 2621


Somebody can help me on this?



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