Pesky Subnets

[Crossy]

OK, consider this network (it's part of our office in BLR).

Router 1

IP 192.168.1.1

Sub mask 255.255.252.0

Router 2

IP 192.168.2.1

Sub mask 255.255.252.0

PC

IP 192.168.1.222

Sub mask 255.255.252.0

If I've got this right I should be able to see both routers from the PC, but I can't Router 2 is only visible if I change the PC to 192.168.2.222 (and then Router 1 disappears).

And no, I can't change any of the IP addresses, fiddle with the masks all I like though

Daft thing is, I CAN see 192.168.2.8

What is going on? How can I fix it? Is there a god?

[harrry]

Have a look at http://www.rolo.org/192-168-1-1.html

Basically you have chosen addresses which are reserved for private networks. The problem with these addresses is that they cannot be passed through a router to another network without using techniques such as NAT to enable them to cross the router barrier.

Edited April 28, 2009 by harrry

[Jdietz]

Change netmask to 255.255.0.0 and all will be well... basically this jams 192.168.x.y all in one segment.

[surface]

Hmmm, 2 routers on 1 subnet? RIP, BGP, OSPF? Do you have any managed switches on the network?

When you say "see" do you mean ping?

Is the desktop getting routes via DHCP?

[Prasert]

OK, consider this network (it's part of our office in BLR).

Router 1

IP 192.168.1.1

Sub mask 255.255.252.0

Router 2

IP 192.168.2.1

Sub mask 255.255.252.0

PC

IP 192.168.1.222

Sub mask 255.255.252.0

If I've got this right I should be able to see both routers from the PC, but I can't Router 2 is only visible if I change the PC to 192.168.2.222 (and then Router 1 disappears).

And no, I can't change any of the IP addresses, fiddle with the masks all I like though

Daft thing is, I CAN see 192.168.2.8

What is going on?

The subnetmask 255.255.252.0 or /22 combines 4 class C networks. Class C networks were used in the previous century, these days all equipment should support VLSM or variable-length-subnet-masks.

The IP range with this subnet: 192.168.0.0 till 192.168.3.255

Valid host addresses are all addresses between these 2 above (1022 addresses).

How can I fix it?

Check if the router that gives you a headache is a real router running software that conforms to the IPv4 standard. It should work!

Bad thing is that when a subnetmask has anything else in it than a 0 or255, most people get totally confused, but it's common practice on the internet to use the smallest possible subnet.

Configure a pc at 192.168.0.5 and one at 192.168.3.234 with a /22 subnet

You'll be able to ping from one to the other (turn off firewall).

The routers should be able to ping each other as well, they are on the same subnet.

Is there a god?

Read the forum rules....

[Crossy]

Thanks chaps, it's working with 255.255.0.0 although I don't really know why it didn't work before.

There are all sorts of switches (managed and non-managed) and hubs in what seems to be a random configuration and I for one am NOT going to attempt to untangle the mess. The very act of entering the network cabinet stops something working and I don't intend getting blamed for that, my bit now functions and I'm happy.