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In an effort to make sure all Windows application that rely on time work (such as RDP), and to make sure logging between computers and router are using the same times, I would like to use NTP technology between my Cisco router, my domain controllers, and all client machines and devices on my network.

My current setup is. Cisco DPC 3908 modem (Provided by Comcast ISP) -> Cisco 1921 ISR K9 -> Netgear 10/100 switch -> Linksys WAP and Connected Servers (all running Windows Server 2008 R2).

Currently, the domain controller is the NTP server, with all Windows clients and other devices getting their time synced using the domain controller.

I would like to have the Cisco 1921 act as a NTP client, and sync it's clock using the server (Windows Domain Controller).

What ports or firewalls are required to stay open in order for this to work? Are there any extra tasks needed other than using the appropriate commands in IOS?

Kevin
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All I had to do on all my Cisco Routers (827/837/877 with iOS 12.3) was the following:

clock timezone gmt 0
clock summer-time BST recurring last Sun Mar 2:00 last Sun Oct 2:00
sntp server 192.168.17.11

Set the sntp server IP to the IP of your windows domain controller that provides NTP Time for the network (In my case this is a standard Windows 2008 Server install)

Then set your timezone (so the router knows how to do clock adjustments) and summer time/daylight savings if you need to for your territory.

From memory only the sntp line was actually required, then you will need to do a reload (Or at least I did) and on rebooting the router contacted the time server and started to sync from it

shawty
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