Subnetting problem

Answered Question
May 28th, 2008

Dear All

Problem: i had given a task to configure the 8 routers that will be connected to the 4 routers at the other end.The configuration will be (8*4)

i.e there will be 8 different wan links that will be connected to the 4 other side links . and main problwm is that any router can connect to any no of routers from the 4 terminating side .

MY Question: This is possible or not ,If possible then how?

My solution to problem: Either it can be done to assing the same subnet ip to all the routers i.e(172.168.1.1/24)

But this scheme has a very less ip available for the use.

I want 100ips at the 1 wan side.

so please suggestme any other wa.

I have this problem too.
0 votes
Correct Answer by PAUL TRIVINO about 8 years 6 months ago

OK, given just the information provided let me make a couple of assumptions - the 8 lines to the (remote? call them B1-8) routers are point-to-point; you *can* assign any (Local? call them A1-4) router to any of the others, but let's do A1 to B1 and B2, A2 to B3 and B4, etc.

You could assign 192.168.1.0/30 to the link A1-B1, and 192.168.1.4/30 to the A1-B2 link, then do 192.168.1.8/30 for A2-B3 and 192.168.1.12/30 to A2-B4. Continuing on you end with A4-B8 as 192.168.1.28/30.

That entire range can be summarized as 192.168.1.0/27. That leaves 192.168.1.32/27, 192.168.1.64/26 and 192.168.1.128/25 open for use, and the latter has 126 usable IP addresses.

Does that help? (Please rate)

Paul

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Correct Answer
PAUL TRIVINO Wed, 05/28/2008 - 09:15

OK, given just the information provided let me make a couple of assumptions - the 8 lines to the (remote? call them B1-8) routers are point-to-point; you *can* assign any (Local? call them A1-4) router to any of the others, but let's do A1 to B1 and B2, A2 to B3 and B4, etc.

You could assign 192.168.1.0/30 to the link A1-B1, and 192.168.1.4/30 to the A1-B2 link, then do 192.168.1.8/30 for A2-B3 and 192.168.1.12/30 to A2-B4. Continuing on you end with A4-B8 as 192.168.1.28/30.

That entire range can be summarized as 192.168.1.0/27. That leaves 192.168.1.32/27, 192.168.1.64/26 and 192.168.1.128/25 open for use, and the latter has 126 usable IP addresses.

Does that help? (Please rate)

Paul

sanjukumarsharma Fri, 05/30/2008 - 00:16

Dear Paul

Thansk for suggesstion,

All that i have is one cisco router that has 2 wic 2t cards. that means i have only four interface (lets name it A1-A4). AT the far end side i have complete different 8cisco routers with wic 1T cards(i.e. B1-B8).

And they are going to connect in the form of

(A1-A4)DTE-DCE---network cloud--DCE-DTE(B1-B8)

THe routers are connecte din this format.

What i am using is that /16network

Ip schmea is on the bassis of location

like A1-192.168.1.100/16

A2-192.168.2.100/16

------and so on

At the other end

B1--192.168.11.199/16(rest ip are for the future use)

B2--192.168.12.199/16

and so on .

Is this going to work ???? (please rate)

As far as your ip schema concern

how can i assing the four ip to link A1?

I am not geeting your Ip schemas point ?

thanks and regards

sanju

PAUL TRIVINO Fri, 05/30/2008 - 08:41

Let me address these inline:

> All that i have is one cisco router that has > 2 wic 2t cards. that means i have only four > interface (lets name it A1-A4). AT the far >end side i have complete different 8cisco >routers with wic 1T cards(i.e. B1-B8).

> And they are going to connect in the form of

> (A1-A4)DTE-DCE---network cloud--DCE-DTE(B1-B8)

> THe routers are connected in this format.

OK, since you've said T1 cards I'm assuming Frame Relay here. I can't give you the configs for that but I assume you'll put two DLCIs/PVCs on each T1 at the "A" end, each PVC going to a "B" router? That might be two subinterfaces per T1 interface, depending on how you configure the Frame stuff (I'm no expert at that).

> What i am using is that /16network

> Ip schmea is on the bassis of location

> like A1-192.168.1.100/16

> A2-192.168.2.100/16

> ------and so on

> At the other end

> B1--192.168.11.199/16(rest ip are for the future use)

> B2--192.168.12.199/16

> and so on .

> Is this going to work ???? (please rate)

I can't rate YOU, you're asking the questions! ;^)

> As far as your ip schema concern

> how can i assing the four ip to link A1?

> I am not geeting your Ip schemas point ?

As I understand it, this won't work, unless your WAN is some form of broadcast-able media. The 192.168.1.100/16 network on A1 includes all of the addresses you've assigned - it's 192.168.0.0 through 192.168.255.255.

My suggested IP scheme assigns a network address to each point to point link (be it T1 or FR or whatever), with the smallest IP address footprint possible (actually I think you can use /31 masks now but I've never done it).

Does that help?

Paul

sanjukumarsharma Sat, 05/31/2008 - 02:05

Dear Paul

As far as the connectivity concern,

These are connected through the frequency bassis using the satellite modems.

so these are not participating in the other network.

Thanks and regards

sanju

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