Subnetting with VLSM IP addressing design
Setotek
Member Posts: 61 ■■□□□□□□□□
in CCNA & CCENT
Hi Everyone,
Practicing for the CCNA and came across a practice question regarding subnetting which involves VLSM. I hope someone can shed some light. Thanks.
The admin received 192.168.151.0 as the network address of a company. The company plans to configure ip subnet-zero and use RIPv2 as the routing protocol.
I dont have a way to upload the diagram but ill describe it the best way i can...
R3
|
SW1 - R1 - R2 - SW2
|
SW3
SW1 - has 11 hosts
SW2 - has 19 hosts
SW3 - has 4 hosts
RW3 - is the ISP router
RW1 and RW2 - connect the switches together using vlsm and ripv2
They list the following ip addresses with subnet mask and youre supposed to apply them to the router interfaces accordingly:
192.168.151.93/30
192.168.151.102/27
192.168.151.92/30
192.168.151.255/25
192.168.151.84/29
192.168.151.72/28
When i calculate which ip addresses to use for each router interface this is what i get:
R1 = 192.168.151.72/28 <-- This will work for SW1 host requirement
R1 = 192.168.151.84/29 <-- This will work for SW3 host requirement
R2 = 192.168.151.102/27 <-- This will work for SW2 host requirement
R3 = 192.168.151.92/30 <-- This will work for the ISP router
However, the answer key shows that the ip addresses are swapped for the below
R1 = 192.168.151.84/29 <-- supposedly for SW2 host requirement
R2 = 192.168.151.102/27 <-- supposedly for SW3 host requirement
Can anyone tell me why that is? To me, the ip addresses and subnet masks will not help with the host requirements at all unless VLSM and RIPv2 are involved in this matter.
Or is it just a plain mistake on printing??
Setotek
Practicing for the CCNA and came across a practice question regarding subnetting which involves VLSM. I hope someone can shed some light. Thanks.
The admin received 192.168.151.0 as the network address of a company. The company plans to configure ip subnet-zero and use RIPv2 as the routing protocol.
I dont have a way to upload the diagram but ill describe it the best way i can...
R3
|
SW1 - R1 - R2 - SW2
|
SW3
SW1 - has 11 hosts
SW2 - has 19 hosts
SW3 - has 4 hosts
RW3 - is the ISP router
RW1 and RW2 - connect the switches together using vlsm and ripv2
They list the following ip addresses with subnet mask and youre supposed to apply them to the router interfaces accordingly:
192.168.151.93/30
192.168.151.102/27
192.168.151.92/30
192.168.151.255/25
192.168.151.84/29
192.168.151.72/28
When i calculate which ip addresses to use for each router interface this is what i get:
R1 = 192.168.151.72/28 <-- This will work for SW1 host requirement
R1 = 192.168.151.84/29 <-- This will work for SW3 host requirement
R2 = 192.168.151.102/27 <-- This will work for SW2 host requirement
R3 = 192.168.151.92/30 <-- This will work for the ISP router
However, the answer key shows that the ip addresses are swapped for the below
R1 = 192.168.151.84/29 <-- supposedly for SW2 host requirement
R2 = 192.168.151.102/27 <-- supposedly for SW3 host requirement
Can anyone tell me why that is? To me, the ip addresses and subnet masks will not help with the host requirements at all unless VLSM and RIPv2 are involved in this matter.
Or is it just a plain mistake on printing??
Setotek
Comments
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Setotek
Member Posts: 61 ■■□□□□□□□□
Adjustment:
When i submitted the question the diagram did not post correctly.
SW3 is connected to R1
R3 is connected to R2
Thanks... -
Gauge
Member Posts: 8 ■□□□□□□□□□
That's definitely wrong. The subnet masks make it an impossibility. The 29-bit mask yields only 8 IPs, or 6 hosts. That can't be used on a network of 19 hosts.
-
techED
Member Posts: 55 ■■□□□□□□□□
From a Modified network, below is the device to subnet.
R3
|
SW1 - R1 - R2 - SW2
|
SW3
R1 = /30
R2 = /29
R3 = /30
SW1 = /27
SW2 = /25
SW3 = /28