One NTP server distributed to multiple networks

[RicksterC]

I'm a relative newbie to LAN switching and Routing and I hope somebody can give me some tips on how to solve the following:

I have a GPS NTP server with a single Ethernet port. I need to distribute this time source to six separate networks but I need to maintain isolation between these networks. The networks are not interconnected in anyway at the moment. Is this possible?

If so, could I accomplish this with a managed switch and VLANs or should I use a router with multiple interfaces? 

Any guidance would be appreciated.

Thanks in advance.

[Leo Laohoo]

If they're not interconnected, then there is no way. 

Ever heard of a cheap GPS-based NTP server using a Raspberry Pi?  Read THIS.

[Joseph W. Doherty]

Unless you follow an approach like what Leo has suggested, you're going to have to interconnect your networks in some fashion, this to allow NTP between devices.

One you have connectivity, you can block all internetwork traffic except that needed to support NTP.

You'll need to decide whether all the networks need to directly access your NTP server (i.e. communicate with its IP), or whether you might extend out a NTP topology. How you approach this will impact how you need to route (or not) between your networks.

[RicksterC]

Thanks Leo and Joseph for your replies.

I should have been clearer in my post, in that I am aware that I need to connect the networks in some way, I'm just not sure how I limit the traffic to just NTP?

Can this be done with a Cisco managed switch and VLANs? or, as I have five different networks, would I also need a router?

Apologies if these are basic questions.

[Leo Laohoo]

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@RicksterC wrote:

I'm just not sure how I limit the traffic to just NTP?

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Either a firewall or ACL.

[johnd2310 · Accepted solution]

Hi,

If your networks are segregated for security reasons, then the best option for you would be to buy an NTP appliance for each of your networks. 

thanks

John