Share network device across 2 networks


Someone has asked me if it is possible to do something and Im not sure.  They have 2 networks both with a Draytek 2820 router.  One is basically a private network for the important people in a company and the other is a public network for the likes of me!  They have one device which they would like to access on both networks.  Is this feasible?  I have asked for the setup of both networks (ip address ranges etc) but Im just trying to get a bit of headway on this.

Many thanks
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Fred MarshallConnect With a Mentor PrincipalCommented:
Where is/are the internet gateways in all this?  I will assume for now that the two networks are *totally* separate and there are two internet gateways.  The other option of course is that there is but one.

When there is but one internet gateway then I've set such things up in a cascade arrangement with the "private" network at the end of the chain.  See the attached.

The first page shows a cascade arrangement where you would put the shared device in the middle LAN.  Users on the middle LAN generally can't reach devices on the lower LAN without routing added.  Users on the lower LAN can generally reach devices on the upper LAN.  Results may vary depending on the equipment but I've not seen that variation so far.
To me it's a bit of a stretch but it might be possible for users on the upper LAN to "sniff" traffic from the lower LAN.  I leave how to do that up to who's interested.

The second page shows a parallel arrangement where you would put the shared device in the upper LAN.  Users on both LANs can obviously reach the internet gateway in this arrangement and so should be able to reach the shared device.
Users can't reach the "opposite" LAN without added routing.

In either case, users on both LANs should be able to reach the shared device.  

Does this match up closely enough to what you're wanting to do?
I really don't see what is complicated about this, unless I am reading this incorrectly. Just put the device on it own network, give access to it from both the private and public network.
Fred MarshallPrincipalCommented:
"Give access to it from ...." is what I understand the question to be.  i.e. How?  Is that right simonwait?
simonwaitAuthor Commented:
Hi.  Im still waiting for more information from the other person but yes the question is how you would give access to it.  The only additional information I have from a 3rd party is that the device is currently on private network (ie the cat5 is patched into the switches which look after the private network)
simonwaitAuthor Commented:
Sorry guys but the fella who originally asked the question has disappeared.  As soon as I know more I will pass it on.
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