Configure and verify NTP as a client
Configure and verify NTP as a client
“Time is inherently important to the function of routers and networks. It provides the only frame of reference between all devices on the network. This makes synchronized time extremely important. Without synchronized time, accurately correlating information between devices becomes difficult, if not impossible. When it comes to security, if you cannot successfully compare logs between each of your routers and all your network servers, you will find it very hard to develop a reliable picture of an incident. Finally, even if you are able to put the pieces together, unsynchronized times, especially between log files, may give an attacker with a good attorney enough wiggle room to escape prosecution.” –Thomas Akin, in Hardening Cisco Routers.
NTP provides us (the network, systems, and security guys) with an easy way to ensure that all of our network devices have the same time. In smaller networks, this is desirable; in large networks, it is a must. In this lab, we’ll configure one Cisco router as both a client (synchronizing time from hosts on the Internet) and server (providing time synchronization to other internal devices).
The physical topology looks like this:
For our demonstration, R1 will be both an NTP client and NTP server while R2 will only be an NTP client. Because we will be synchronizing R1′s time with a host on the Internet, R1 will need connectivity to the Internet for this demonstration; R2 will not. R1′s actual connectivity to the Internet is irrelevant and out of the scope of this demonstration.
• R1 will synchronize time against nist.netservicesgroup.com (64.113.32.5).
• R2 will synchronize time against R1 (172.16.12.1).
• NTP synchronization between R1 and R2 will be authenticated, using a key of “ThereIsTimeForEverything“.