gatway/routing question...can anyone help explain this?

mastercorm

here is a sample question i found.

From Host A you have the follwing IP configuraation: IP address: 192.168.1.242 Default Gateway: 192.168.1.241 Subnet Mask: 255.255.255.240 Which of the following IP addresses will require routing to a separate network? (Select 2)
192.168.1.24
192.168.1.249
192.168.1.254
216.168.1.240

Obviously the 216 IP is on a seperate network. However, how do i determine which other address needs to be routed differently? As far as I can tell, they're all Class C, and have the same network ID.
Can anyone help explain this?

kenny504

If I understand your question coreectly you basically want to find out which of those ip addresses are on a different network. Hence, will have to be routed to a different network.

Well the answer is "A" 192.168.1.24. and obviously D


The reason why i gave this answer is because all the other ip addresses are in the same network except for this one.

Seeing that 255.255.255.240 is ure subnet mask that means that your first subnet will be: 192.168.1.16 and your last address in that subnet will be 192.168.1.31 so "192.168.1.24 is in that first subnet.

Your last subnet will be 192.168.1.240 and your last address in that subnet will be 192.168.1.255 so the other three addresses fall right into that subnet. Of course 192.168.1.240 being ure network address it will not be used for any host unless your using subnet-zero. But hey it still is in that subnet. So there it is..... i hope you understand my answer.

Kenny.

NightShade1

Ok let see if i can help

This is a simple subnetting question

You got the IP addresss and the default gateway which is supposed to be configured in the proper way so what we want here is to find out here is

1-We gotta see which is the incremetal interval of the network

2-then we look which network belongs to the IP address: 192.168.1.242 Default Gateway: 192.168.1.241 which should be in the same network if they are correctly configured


Okay now how we find this incremental interval?

You see the mask which is 255.255.255.240
This means the incremental interval is 16
How i know this?
ill tell you the easy way if you wanna how this is done well i guess i can explain it also but for now ill tell you the easy one

if you got
255.255.255.128=incremental interval is 128
255.255.255.192=incremental interval is 64
255.255.255.224=incremental interval is 32
255.255.255.240=incremental interval is 16
255.255.255.248=incremental interval is 8
255.255.255.252=incremental interval is 4
255.255.255.254=incremental interval is 2


So well the thing is that you know that the incremental interval is 16

Now you gotta find the network that those ips belongs
you will have
Network adress

---

Usable IPs

---

BroadCast Address
192.168.1.0

---

192.168.1.1--192.168.1.14

---

192.168.1.15
192.168.1.16

---

192.168.1.17--192.168.1.30

---

192.168.1.31
192.168.1.32

---

192.168.1.33--192.168.1.46

---

192.168.1.47
.
.
.
192.168.1.240

---

192.168.1.241--192.168.1.254

---

192.168.1.255


As you can see your IPs belongs to network 192.168.1.240
And your ip address and the default gateway are using Usables Ips so its all cool

Now let see your question
You wanna know which Ips doesnt belong to that network(as far i understand for whatyou were asking)
Well you can see it easy now

192.168.1.24 It DONT belong to the network
192.168.1.249 It BELONG
192.168.1.254 it BELONG
216.168.1.240 it DONT belong to the network

So as you can see asnwer is A and D

What you need is learn how to subnet.... if you need a manual or something i can give you one just ask

mastercorm

K, thanks guys. I appreciate it. In the class i'm taking, this is what we've been going over for 3 days, so i'm starting to comprehend it better. kinda confusing at first though. I'm grasping it now though. I actually have a final tonight, and the teacher said at least 5 questions are related to subnetting, so I've been busy studying that.

kujayhawk93

mastercorm wrote:

K, thanks guys. I appreciate it. In the class i'm taking, this is what we've been going over for 3 days, so i'm starting to comprehend it better. kinda confusing at first though. I'm grasping it now though. I actually have a final tonight, and the teacher said at least 5 questions are related to subnetting, so I've been busy studying that.

This might be something you need to know for your final, but it goes way, way, WAY beyond the scope of the Net+ test. As long as you know the address ranges and default gateways for class A, B, and C, then you're good.

NightShade1

If you planning in taking CCNA after better start learning it from now.... this is something you should be able to do in mind, at least in CCNA because well at least that saved me LOT of time in the exam.

mastercorm

yeah, i definitely intend to know it. i just had my final the other night and i think i got at least an 89 on it. I hate not knowing stuff anyway. Plus, I definitely will need it, so it's not something to gloss over. last thing i want is to be at an interview and have a boss ask me something about subnetting and not know it. that'd suck.

eventually, I plan on getting my MCSE and earning some good cash. One cert. at a time though. Sucks that they're so much money.