Help! How can I connect to resources across multiple routers?

[admorphit]

Hi,

I have two routers (A, B) connected together through cable.
2 computers are connected to router A and a computer is connected to
router B, all via cable.

Router A has IP of: 192.168.1.1
Router B has IP of: 192.168.2.1 and 192.168.1.4

[Comp1] \
=|Router A|= -------------- =|Router B|= ----- [Comp3]
[Comp2] /

Comp1 (192.168.1.2) talks without problems to Comp2 (192.168.1.3), but
neither Comp1 nor Comp2 can talk with Comp3 (192.168.2.2).

How can I get Comp3 to share resources with the other comps?

Any help would be greatly appreciated,

Tim.

 

[Mike Scott]

Hi,

I have two routers (A, B) connected together through cable.
2 computers are connected to router A and a computer is connected to
router B, all via cable.

Router A has IP of: 192.168.1.1
Router B has IP of: 192.168.2.1 and 192.168.1.4

[Comp1] \
=|Router A|= -------------- =|Router B|= ----- [Comp3]
[Comp2] /

Comp1 (192.168.1.2) talks without problems to Comp2 (192.168.1.3), but
neither Comp1 nor Comp2 can talk with Comp3 (192.168.2.2).

How can I get Comp3 to share resources with the other comps?

Any help would be greatly appreciated,

Tim.

Looks like your addressing is wrongly set up. The way your diagram is
drawn you have /3/ subnets. Comp1, comp2 and the left side of router A
should be on one network, the R of A and the L of B on another, and the
R of B and Comp3 on the third. Routers have at least 2 IP addresses -
that's what they do: route between different networks. But even if you
get the addressing correct, you need to think carefully about routing
protocols, and this may depend an what your routers are exactly -
/somehow/ Comp1 needs to know that packets for comp3 should be sent to
router A, for example (and not, say, to comp2).

But why the complexity? What's wrong with a simple switch, or cascaded
switches?

 

[admorphit]

Hi,

I have two routers (A, B) connected together through cable.
2 computers are connected to router A and a computer is connected to
router B, all via cable.

Router A has IP of: 192.168.1.1
Router B has IP of: 192.168.2.1 and 192.168.1.4

[Comp1] \
=|Router A|= -------------- =|Router B|= ----- [Comp3]
[Comp2] /

Comp1 (192.168.1.2) talks without problems to Comp2 (192.168.1.3), but
neither Comp1 nor Comp2 can talk with Comp3 (192.168.2.2).

How can I get Comp3 to share resources with the other comps?

Any help would be greatly appreciated,

Tim.

Looks like your addressing is wrongly set up. The way your diagram is
drawn you have /3/ subnets. Comp1, comp2 and the left side of router A
should be on one network, the R of A and the L of B on another, and the
R of B and Comp3 on the third. Routers have at least 2 IP addresses -
that's what they do: route between different networks. But even if you
get the addressing correct, you need to think carefully about routing
protocols, and this may depend an what your routers are exactly -
/somehow/ Comp1 needs to know that packets for comp3 should be sent to
router A, for example (and not, say, to comp2).

But why the complexity? What's wrong with a simple switch, or cascaded
switches?

Sorry for the delayed response, I haven't checked back here in a
while.
I'm still confused perhaps because my ASCII diagram isn't very clear.
I created a visual one here:http://www.geocities.com/digitalcomplexity/
_source/hometopology.png
which may help better explain my setup.

Again my problem is that Computer A and B can't connect to any
computers on the right of the diagram, but all computers on the right
can connect to the internet and ping computers on the left (ie.
computers A and B).
I'm really lost here and don't know why this is the case.

Thanks again.

 

[Mike Scott]

admorphit wrote:
....

Sorry for the delayed response, I haven't checked back here in a
while.
I'm still confused perhaps because my ASCII diagram isn't very clear.
I created a visual one here:http://www.geocities.com/digitalcomplexity/
_source/hometopology.png
which may help better explain my setup.

Again my problem is that Computer A and B can't connect to any
computers on the right of the diagram, but all computers on the right
can connect to the internet and ping computers on the left (ie.
computers A and B).
I'm really lost here and don't know why this is the case.

Thanks again.

OK, that's clearer. I may even see what's wrong

I think you'll find that a cheap and simple router only knows about two
segments - a LAN and a WAN. It will assume that anything it sees that's
not headed for the LAN must be shoved out of the WAN port, and that
whatever is upstream of that will deal with the data correctly.

In your case, router B will direct any traffic not on 192.168.2 down its
"WAN" port - in other words to router A, which will again direct its own
own local traffic to its LAN ports, and anything else to the "real" WAN.
That will work.

However, router A will behave similarly. Any non-192.168.1 traffic will
be directed down its WAN port. That's OK, /except/ that traffic intended
for 192.168.2 will be sent that way as well - which will effectively
block traffic from 192.168.1 to 192.168.2.

(I'm fudging an issue here; the gist should be correct though. I hope ).

I would strongly suggest that you replace router B with a wireless
access point and switch, and merge both networks into one. Life will be
much, much easier. I can't see any reason for your setup, unless you
need to firewall off one group of machines from the other. If you
absolutely must have two LANs, consider using a *BSD machine with
multiple NICs, for example, in place of both routers: this can then make
proper routing decisions.

 

[admorphit]

admorphit wrote:

...





OK, that's clearer. I may even see what's wrong

I think you'll find that a cheap and simple router only knows about two
segments - a LAN and a WAN. It will assume that anything it sees that's
not headed for the LAN must be shoved out of the WAN port, and that
whatever is upstream of that will deal with the data correctly.

In your case, router B will direct any traffic not on 192.168.2 down its
"WAN" port - in other words to router A, which will again direct its own
own local traffic to its LAN ports, and anything else to the "real" WAN.
That will work.

However, router A will behave similarly. Any non-192.168.1 traffic will
be directed down its WAN port. That's OK, /except/ that traffic intended
for 192.168.2 will be sent that way as well - which will effectively
block traffic from 192.168.1 to 192.168.2.

(I'm fudging an issue here; the gist should be correct though. I hope ).

I would strongly suggest that you replace router B with a wireless
access point and switch, and merge both networks into one. Life will be
much, much easier. I can't see any reason for your setup, unless you
need to firewall off one group of machines from the other. If you
absolutely must have two LANs, consider using a *BSD machine with
multiple NICs, for example, in place of both routers: this can then make
proper routing decisions.

Mike,

Thanks for your prompt response.
I did notice that packets I pinged from router A go out the WAN port
(tracert 192.168.2.1).
The wifi Router B was a gift and replaced what used to be plain old 5
port switch. The network was fine back then when everything was in the
scope of 192.168.1.x

I can't go back to that because there are now two wireless devices
which need to connect to the internet.
Hmm.. but perhaps the most feasible solution is the one you suggested,
getting an access point.

Thanks for your help.
Tim.