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Basic Routing Question

Hi,

I've just installed a frame-realy lab for the first time and started using it. It's really basic with one hub router (R1) and two spoke routers (R2 and R3). I've setup two subnets 192.168.100.0/30 and 192.168.100.4/30.

Although I can ping the spoke to the hubs respectively, the confusing part is when I run "show ip route", for both the spokes I get the following:

R2:

Gateway of last resort is not set

     192.168.100.0/30 is subnetted, 1 subnets
C       192.168.100.0 is directly connected, Serial0/0.1

R3:

Gateway of last resort is not set

     192.168.100.0/30 is subnetted, 1 subnets
C       192.168.100.4 is directly connected, Serial0/0.1

For the hub I get:

R1:

Gateway of last resort is not set

     192.168.100.0/30 is subnetted, 2 subnets
C       192.168.100.4 is directly connected, Serial0/0.2
C       192.168.100.0 is directly connected, Serial0/0.1

My question is why do the spokes and the hub say the following:

     192.168.100.0/30 is subnetted, 2 subnets

Shouldn't R2 show

     192.168.100.0/30 is subnetted, 1 subnets
C       192.168.100.0 is directly connected, Serial0/0.1

and R3 shoudl show:

     192.168.100.4/30 is subnetted, 1 subnets
C       192.168.100.0 is directly connected, Serial0/0.1

Can someone please explain this to me?

Many thanks

Dan

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: Basic Routing Question

dan_track wrote:

Thanks Jon,

Silly me in my hurry I got things the wrong way round, what I meant to say was shouldn't

R3 be:

     192.168.100.3/30 is subnetted, 1 subnets
C        192.168.100.4 is directly connected, Serial0/0.1

Ending with .3 will cover the connected subnet. Ending with .0 will not cover that network.

and R2 should be:

     192.168.100.0/30 is subnetted, 1 subnets
C        192.168.100.0 is directly connected, Serial0/0.1

Also in R1

     192.168.100.0/30 is subnetted, 2 subnets
C       192.168.100.4 is directly connected, Serial0/0.2
C       192.168.100.0 is directly connected, Serial0/0.1

where it states "     192.168.100.0/30 is subnetted, 2 subnets", how can that be subnetted into two? "192.168.100.0/30" only covers teh first subnet it can't cover teh subnet 192.168.100.3/30?

Obviously I must missing something

Thanks

Dan

Dan

192.168.100.0 255.255.255.252 =

subnet = 192.168.100.0

2 host addresses = 192.168.100.1 & 192.168.100.2

broadcast address = 192.168.100.3

so your next subnet is

192.168.100.4 255.255.255.252 =

subnet = 192.168.100.4

2 host addresses = 192.168.100.5 & 192.168.100.6

broadcast address = 192.168.100.7

All R1 is saying is that it is aware of 2 subnets of the 192.168.100.0 network using the 255.255.255.252 mask ie. 192.168.100.0/30 and 192.168.100.4/30.

Jon

3 REPLIES
Hall of Fame Super Blue

Re: Basic Routing Question

Dan

R3:

Gateway of last resort is not set

     192.168.100.0/30 is subnetted, 1 subnets
C       192.168.100.4 is directly connected, Serial0/0.1

the above is correct because the subnet is 192.168.100.4 255.255.255.252


and R3 shoudl show:

     192.168.100.4/30 is subnetted, 1 subnets
C       192.168.100.0 is directly connected, Serial0/0.1

this would not be correct because the subnet is not 192.168.100.0 255.255.255.252 as that is assigned between R1 and R2.

Jon

New Member

Re: Basic Routing Question

Thanks Jon,

Silly me in my hurry I got things the wrong way round, what I meant to say was shouldn't

R3 be:

     192.168.100.3/30 is subnetted, 1 subnets
C        192.168.100.4 is directly connected, Serial0/0.1

Ending with .3 will cover the connected subnet. Ending with .0 will not cover that network.

and R2 should be:

     192.168.100.0/30 is subnetted, 1 subnets
C        192.168.100.0 is directly connected, Serial0/0.1

Also in R1

     192.168.100.0/30 is subnetted, 2 subnets
C       192.168.100.4 is directly connected, Serial0/0.2
C       192.168.100.0 is directly connected, Serial0/0.1

where it states "     192.168.100.0/30 is subnetted, 2 subnets", how can that be subnetted into two? "192.168.100.0/30" only covers teh first subnet it can't cover teh subnet 192.168.100.3/30?

Obviously I must missing something

Thanks

Dan

Hall of Fame Super Blue

Re: Basic Routing Question

dan_track wrote:

Thanks Jon,

Silly me in my hurry I got things the wrong way round, what I meant to say was shouldn't

R3 be:

     192.168.100.3/30 is subnetted, 1 subnets
C        192.168.100.4 is directly connected, Serial0/0.1

Ending with .3 will cover the connected subnet. Ending with .0 will not cover that network.

and R2 should be:

     192.168.100.0/30 is subnetted, 1 subnets
C        192.168.100.0 is directly connected, Serial0/0.1

Also in R1

     192.168.100.0/30 is subnetted, 2 subnets
C       192.168.100.4 is directly connected, Serial0/0.2
C       192.168.100.0 is directly connected, Serial0/0.1

where it states "     192.168.100.0/30 is subnetted, 2 subnets", how can that be subnetted into two? "192.168.100.0/30" only covers teh first subnet it can't cover teh subnet 192.168.100.3/30?

Obviously I must missing something

Thanks

Dan

Dan

192.168.100.0 255.255.255.252 =

subnet = 192.168.100.0

2 host addresses = 192.168.100.1 & 192.168.100.2

broadcast address = 192.168.100.3

so your next subnet is

192.168.100.4 255.255.255.252 =

subnet = 192.168.100.4

2 host addresses = 192.168.100.5 & 192.168.100.6

broadcast address = 192.168.100.7

All R1 is saying is that it is aware of 2 subnets of the 192.168.100.0 network using the 255.255.255.252 mask ie. 192.168.100.0/30 and 192.168.100.4/30.

Jon

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