Network design

[1028]

hello,
can anyone tell me whether or not the following network design is problematic; i have one router configured to have 2 subnet interfaces. Say, one interface is 10.1.0.1/16 and the other 10.2.0.1/16.
And, one PC(10.1.0.2) is connected to 10.1.0.1 interface.
And, L2 switch is connected to 10.2.0.1 interface. and, another two routers linked to the L2 switch--one router(A) is 10.2.10.1/16, and the other(B) 10.2.20.1/16. And, onc PC(10.2.20.2/16) is connected to router(B).
can 10.1.0.2(PC1) communicate the 10.2.20.2(PC2)?

maybe. picture like this;
Router(10.1.0.1/16)----PC1(10.1.0.2)
(10.2.0.1/16)
|
L2 Switch(no ip)---routerA(10.2.10.1/16)---PC(10.2.10.2/16)
|
routerB(10.2.20.1/16)
|
PC2(10.2.20.2/16)

any comments will be appreciated. thank you.

 

[jimmyzz]

1028,
I'd recommend using a 24-bit mask for the networks for simplicity in your network design. You may get some confusion with network boundaries. For example, using a 16-bit mask 10.2.10.1 and 10.2.20.1 are summarised as 10.2.0.0

JimmyZ

 

[1028]

thank you, JimmyZ. however, it still doesn't answer to my question. as you commented, say i used 24-bit mask. then, it would be like this;

Router(10.1.0.1/24)----PC1(10.1.0.2)
(10.2.0.1/24)
|
L2 Switch(no ip)---routerA(10.2.0.2/24)---PC3(10.2.0.4/24)
|
routerB(10.2.0.3/24)
|
PC2(10.2.0.5/24)

can PC1 communicate to PC2? will the packet(unicast) go to routerA, routerB or both?

 

[jimmyzz]

1028,
Your latest diagram is completly different from your original. Your 2nd diagram has only two subnets, 10.1.0.0 and 10.2.0.0. As 10.20.0.2/3/4/5 are all in the subnet, I don't see why you need both routerA and routerB to seperate PC3 and PC2. If you want to create 3 subnets then as long as routerA acts as an intermediate router between the subnets (ie.. has an interface into both LAN1 and LAN3) then you should have full routing. Your design should look more like this:

ROUTERC-e0(10.1.0.1) -> LAN1(PC1=10.1.0.2)
|e1(10.2.0.1)
|
SW ---e1(10.2.0.2)ROUTERAe0(10.4.0.1)-->LAN2(PC2=10.4.0.2
|
|e1(10.2.0.3)
ROUTERB -e0(10.3.0.1)-> LAN3(PC3=10.3.0.2)

There is a common network between RA,RB and RC which is 10.2.0.0. This common interface can be a second network interface, or secondary IP, or serial interface connecting the sites via a Frame Relay WAN, etc..

JimmyZ

 

[1028]

at the original diagram, i was also trying to picture diagram using only 2 subnets... and, yes, utilizing just 3 subnets is the right way to do. but, i'm curious if THREE routing interfaces in the same subnet are connected to each other, can routing occur properly? so, on my second diagram, will Router route packet from PC1 to PC2 to routerA or routerB?

 

[tschouten]

It depends on what routing protocol you are using. With EIGRP it might send the first packet to RouterA, RouterA would forward the packet and also send out a notification PDU to say you can better Reach PC2 through RouterB. Then Router will start using RouterB for this specific Network Flow. With OSPF, it would of course choose the shortest path to its destination.

 

[kittenhammer]

>but, i'm curious if THREE routing interfaces in the same
>subnet are connected to each other, can routing occur
>properly? so, on my second diagram, will Router route
>packet from PC1 to PC2 to routerA or routerB?

There's no problem having three router interfaces connected to each other on the same subnet, if that's what you're wondering... the problem in this scenario is that you're using the same networks behind more than one router. That will cause issues when more than one router is saying "Hey, I can get to 10.2.0.0/24 with metric x" and the top router needs to decide whom to believe... and it won't care whether it's trying to send data to 10.2.0.5 or 10.2.0.4.