Packet Tracer Lab help

jrmeulemans

So I'm stuck on this step, not understanding what they want:

3. The Headquater has given IP address
range 192.168.0.0/27 for the network
behind our router, then you have to:
3.1 enable interface Fa0/0 and set
IP address/Subnet Mask to be the
last IP of this subnet that has
10 host as members.
3.2 enable interface Fa0/1 and set
IP address/Subnet Mask to be the
last IP of this subnet that has
5 host as members.
3.3 Set IP address/Subnet Mark of Host1
in each LAN to be the first IP of its
own subnet, and set IP of gateway also


If this network is already subnetted (borrowed 3 bits), why are they asking about 10 and 5 host subnets, when each subnet allows for 30? Here is what i have worked out:

192.168.0.x
255.255.255.11100000
8 subnets
30 hosts


network blocks:
.32
.64
.96
.128
.160
.192
.224

Thanks for any help :P

jrmeulemans

I might add that i got these labs from the CCNA forums at the cisco learning network...so if it is above ICND1 requirements, I guess i don't have to worry about it yet.

Selfmade

you're using Variable Length Subnet Masking, or VLSM, all you have to do is apply what you learned in there to be able to do that.

it says 192.168.0.0/27 is your starting address block

they want you to build a subnet for only 10 hosts

you use the power of 2 to figure out how many you need to achieve that.

2^1 = 2
2^2 = 4
2^3 = 8
2^4 = 16

since they want 10 hosts, you have to go with 16, because 2, 4, and 8, won't meet the requirements

so now you have an address block of 16

the first ip address in the subnet is reserved as the Network Identifier, and the last ip address in the subnet is reserved as the Broadcast IP address.

you will have 192.168.0.0 as your network id, you will have 192.168.0.1 as your first useable ip host address, while 192.168.0.14 is the last useable host address, so you will use 192.168.0.14 as your router's ip address. 192.168.0.15 is reserved as the broadcast address for this subnet. The subnet mask for this one will be /28

Now, for your 5 host subnet, you will need at least 8, so you will increment by 2^3 which gives you 8.

your starting network identifier IP address will be 192.168.0.16 and the broadcast ip address will be 192.168.0.23. your router will be assigned the 192.168.0.22 for it's ip address on fa0/1. The subnet mask for this one will be /29

really simple once you get the hang of it. All you have to do is when you're using subnets of any length, is that you have to borrow 2 from whatever the final number is, because one is reserved as a network identifer IP address, and the other is reserved as a broadcast address. Whatever remains are useable host addresses that can be applied to interfaces or applied to computer hosts.

Hope that helps!

Also, here http://www.vlsm-calc.net/ That website has a built in VLSM calculator for you to use, for your first few assignments, use it to get an idea of what you need to do, and as you progress, do the work on your own without the calculator, THEN use the calculator to check your answers, that will help you tremendously.

Also remember, all you're trying to do when they tell you how many hosts they want is to find the subnet range that satisfies that requirement.

For instance, if you're asked to fit 120 hosts into a subnet that only has 30 addressable spaces, it's not possible, you would only manage to fit 30 in. but if you increased the addressable spaces to 126, then you could fit that in, it would have an addressable range of X.X.X.1 to X.X.X.126 and would be all on the same subnet

If they said after that they wanted you to make another subnet with 10 hosts

You'd just increment the .128 network by 16 to make enough space for 10 hosts (up to 14 hosts would fit in this subnet)

so your addressable range would be from .129 to .143. Now, if they said add one more subnet for up to 5 hosts, you'd increment it by 8, because it allows you to put 5 hosts inside the subnet while still leaving 2 ip addresses for the NID and Broadcast IP address. So that one would be started with .144 as the NID, and .145 as the first useable host address to .151 as the broadcast address and .150 as the last useable host address.