[ntp:questions] Cisco switches in internal time reference pool

Jan Ceuleers janspam.ceuleers at skynet.be
Sat Mar 3 13:00:17 UTC 2007


Timo Ruiter wrote:
> I'm building a pool of internal time servers (which will run in stratum 
> 2) that will be used for synchronizing time for all other computers in 
> the network.
> Is it a good idea to include some cisco switches (say two) into the 
> pool?  Do they make a reliable time source when used in symmetrical 
> active mode using a statement like "ntp peer ntp2.local.net key 42" in IOS?

It depends. How important is accuracy? How many NTP clients per switch? 
What is the CPU load on these switches, and how worried are you about 
CPU load on them? How trustworthy are the clients (e.g. how much do you 
trust the clients not to launch a DoS attack against your IP 
infrastructure, intentionally or otherwise)?

In my opinion it is unwise to use an embedded NTP server (i.e. an NTP 
server that is included within a specialised platform whose primary 
purpose is not time keeping, such as a router, media gateway, ...), 
unless accuracy, resource usage and security are all secondary to the 
cost savings as compared to running ntpd on a "proper" server.

Cheers, Jan

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