Set / sync router Clock With NTP Server on GNS3

How to sync router time from internet?

The Network Time Protocol (NTP) is a protocol used for synchronizing the clocks of network devices over data networks.  In Cisco router sometimes obtaining the correct time is extremely important because a variety of services depend on it. The logging service shows each log entry with the date and time so for the accurate data you need the updated time and date at every time. Similarly in configuring some routing protocol’s authentication you also need to have the updated and accurate time on the every router on which you want to enable the authentication. You can sync your router’s time and date with NTP server. You can use some internet NTP server or own master NTP server from within your internal network if you have.  In this gns3 lab we will learn that how we can perform NTP configuration on Cisco router and can sync your router time with the internet NTP server.

In this lab we have three routers R1, R2 and R3. R1 is connected to internet.

Labs Objectives:

·         Configure R1 for automatically sync its time from internet NTP sever and configure as NTP master.

·         Configure R2 and R3 as NTP client and enable them to update their time from R1.

For configuring this gns3 lab you need internet connectivity for accessing the live NTP server from your internal GNS3 router. For providing the internet connectivity on R1 you have to add a cloud for network nodes in gns3 then associate your physical network interface with it, e1/0 is the interface that is connected to your physical interface (cloud) so you must assign IP address from same subnet that your physical interface have. Since my physical interface has IP with gateway therefore I have assign to e1/0.

R1 configuration:


config t

interface e1/0

ip address

no shutdown


ip route (for providing internet access)


After the above configuration you must able to ping your gateway and any internet address.

NTP configuration:



You can find IP address of live NTP server by pinging “”

R1(config)# Ntp server

R1(config)#ntp server master

You can verify the NTP configuration by following commands:

R1(config)#show NTP status

R1(config)#show ntp clock

R1(config)#show ntp association 

Following configuration create the connectivity with R2 and R3.

R1(config)#inter e1/1

R1 (config-if)#ip address

R1 (config-if)#no shut

R1 (config-if)#inter e1/2

R1 (config-if)#ip address

R1 (config-if)#no shut


R2 and R3 configuration:

Configure R2 and R3 as NTP client and enable them to update their time from R1.


R2(config)#inter f0/0

R2(config-if)#ip address

R2(config-if)#no shut


R2(config)#ntp peer

show ntp status

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