VLAN subnets and routing

[jrlowe86IT]

Hi,

A couple of years ago I had a vlan which was something like this 192.168.200.0/22.  I'm looking to this again but I want to make it 192.168.0.0/16.

I've forgotten the original setup of this, so.... I'm connecting a router to a swtich.  On the router interface I've assigned the IP address 192.168.1.250.  If I were connecting a device that was on something like 192.168.100.1, would using 192.168.1.250 be fine as the next hop?

Thanks

[daniel.dib]

It depends on the network mask. If you are using a /16 at both ends then yes they are in the same network. Usually it's not recommended to use such large subnets but it can be done.

Daniel Dib
CCIE #37149

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[devils_advocate]

192.168.0.0 as a /16 means 192.168.anything.anything.

192.168.1.250 and 192.168.100.1 would be in the same network if you were using 255.255.0.0 (/16) as a subnet mask.

As mentioned by Daniel though, this is a large subnet mask to use so if this is in a production network, you need to have a reason to use it otherwise you could be asking for trouble later on. Can you imagine the broadcasts on a /16 busy production network??

[jrlowe86IT]

Well it will only be traffic from desktops of about 80 and 1 file server, so there shouldn't be too many broadcasts going on.

[devils_advocate]

If that's the case, my question would be why a /16 mask?

A standard /24 would be ample for that?

[jrlowe86IT]

It was originally set up to use a couple of different proxies, a couple of ranges with no proxy, and then wireless and server have their own, too.  The /16 would basically allow things to stay consistent, but with a few changes I could reduce it to /22 or so.

It was using a very old router (not cisco) which allowed them to create sub vlans of 10.  For example 10-2 for 192.168.2.X, 10-3, for 192.168.3.X etc, which isn't possible with the router I have.

[Richard Burts]

I am not quite clear on what you are trying to achieve. But I do have this comment. The Cisco router should accept the configuration of 192.168.1.250 255.255.0.0. But depending on the OS of the connected hosts there may be problems where the OS considers an address in 192.168.x.x to be class C and will not accept a default gateway which it considers to be in a different network. If you were doing this in network 10.0.0.0 it would be safer than doing it in 192.168.

HTH

Rick