Discontigous network -- is this not possible?

I have 2 buildings

Building A has hosts
192.168.1.1 /24
192.168.1.2 /24
192.168.1.3 /24

Building B has hosts
192.168.1.4 /24

They are connected by three routers on a point to point

R1

R2----R3

Where R1 is in Building A, and R3 is in Building B

All these hosts are in the same subnet!!!!

So how does R2 know where to route packets? Since routers only know the network addresses

For example what if I make R2 ping 192.168.1.4 -- wouldn't it get confused? Or this design wrong? Can you not have broadcast through routers? Then how do VLANs in far away locations work?

I know pretty basic, but I'm confused.

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Comments

NetworkVeteran

There are many explanations and not enough info to know for certain--

+ The hosts in Building 1 & Building 2 may be prohibited from communicating outside their buildings.
+ The routers may be configured with proxy-arp (not with these addresses, but with similar ones).
+ The routers may be configured to act as switches. Real routers can usually do that.
+ The routers may be configured to use Network Address Translation.

mguy

none of that advanced configuration at all.

R1 and R3 configured to

router rip
version 2
network 192.168.1.0

rip works perfects on all

NetworkVeteran

Since you have access to the configurations, post "show ip route" for each device.

There are still many possibilities, such as host routes.

georgemc

NetworkVeteran wrote: »

Since you have access to the configurations, post "show ip route" for each device.

There are still many possibilities, such as host routes.

NV,

I'm often confused by Mguys posts, but in this case I believe he's asking HOW to do it, vice HOW DID they do it. My impression is that he does not have a working configuration doing what he's talking about in the original post.

Or maybe I'm just confused again.

georgemc

mguy wrote: »

Building B has hosts
192.168.1.4 /24

:

mguy,

What is the assigned gateway for 192.168.1.4 /24 and where is is located(what router is it on)?

Geographically disparate VLANs(same VLAN in 2 or more locations) work at layer 2 with the gateway of said VLAN being in a centralized location. This is not done much anymore.

What you're doing here really does not fall under the definition of what we'd think of as "discontiguous" subnets.

As NetVet requested, the SH IP ROUTE and possibly the SH RUN for each router would be very helpful.

mguy

georgemc wrote: »

NV,

I'm often confused by Mguys posts, but in this case I believe he's asking HOW to do it, vice HOW DID they do it. My impression is that he does not have a working configuration doing what he's talking about in the original post.

Or maybe I'm just confused again.

I apologize for the confusion. You are right, I don't have a configuration, this is more theoretical.

Say you have a sales building this building is VLAN sales that is network say 192.168.1.0 /24

Sales guy goes to another building, say engineering, but retains his ip address. His default gateway is not changed, but router R3 is configured with subinterface.

Now we have an outsider and he wants to ping the sales guy through R2 (which is the corporate gateway). How does R2 know where to send it?

(sales)R1

R3(engineering + the sales guy)

NetworkVeteran

mguy, the way this works in the real world--

Building A uses 192.168.1.0/24. Building B uses 192.168.2.0/24. When the sales guy plus into the second building, his PC sends a DHCP request and is automatically assigned a Building B IP address.

If you want end-to-end VLANs, convert R1/R2/R3 to switches. Your network will be cheaper. It's not Cisco's preference, and it's not the model I see deployed at the majority of large corporations, but many carriers manage to pull-off huge switched domains.

The middle device (R2/S2) is only needed if there are many buildings. In most cases, if a middle-device were needed, you would add two of them, for redundancy.