topic Re: how to check if devices are on same network or not? in Switching

how to check if devices are on same network or not?

mahesh18 — Wed, 06 Mar 2019 10:54:41 GMT

i have one host IP

172.16.10.100/16 and another host

172.16.20.200/24

how can we check that if they are in same network or not?

many thanks

mahesh

Re: how to check if devices are on same network or not?

Jon Marshall — Wed, 10 Dec 2008 21:10:08 GMT

Mahesh

Not sure i fully understand.

172.16.10.100/16 is host 10.100 on network 172.16.

172.16.20.200/24 is a host 200 on network 172.16.20.

is there some connectivity issue you are having.

Jon

Re: how to check if devices are on same network or not?

royalblues — Wed, 10 Dec 2008 21:10:52 GMT

use any online subnet calculator

http://jodies.de/ipcalc

Narayan

Re: how to check if devices are on same network or not?

mahesh18 — Wed, 10 Dec 2008 21:20:43 GMT

Hi jon,

i want to know if these two devices are on same subnet or not?

if they are on different subnet how can we check that?

many thanks

Re: how to check if devices are on same network or not?

Jon Marshall — Wed, 10 Dec 2008 21:27:10 GMT

Mahesh

No they are not on the same subnet - see my previous answer.

Jon

Re: how to check if devices are on same network or not?

Edison Ortiz — Wed, 10 Dec 2008 21:28:05 GMT

The host 172.16.10.100 255.255.0.0 is on the same network as 172.16.20.200 255.255.255.0 but 172.16.20.200 255.255.255.0 is not in the same network as 172.16.10.100 255.255.0.0 - thus you will have connectivity issues between these devices as the path from one device to another may be different.

Edison.

Re: how to check if devices are on same network or not?

royalblues — Wed, 10 Dec 2008 21:30:10 GMT

Yes they are in the same subnet

The first ip address is part of the major subnet 172.16.0.0/16. 16 here would denote the network bits leaving the other 16 as host bits

The IP address 172.16.200.0/24 is a subset of the major subnet above

Time to read some ip addressing

http://www.ralphb.net/IPSubnet/

Narayan

Re: how to check if devices are on same network or not?

Jon Marshall — Wed, 10 Dec 2008 21:35:53 GMT

Narayan, Edison

First time we have all disagreed.

Narayan - yes in same subnet

Edison - yes for one, no for the other

me - no for both.

How do we decide this 🙂

Jon

Re: how to check if devices are on same network or not?

royalblues — Wed, 10 Dec 2008 21:40:46 GMT

Edison,

I think you put it the reverse way

The address 172.16.20.200/24 is on the same network as 172.16.10.100/16

Narayan

Re: how to check if devices are on same network or not?

mahesh18 — Wed, 10 Dec 2008 21:41:50 GMT

Hi ediortiz,

can u please explain me in more detail

many thanks

mahesh

Re: how to check if devices are on same network or not?

Edison Ortiz — Wed, 10 Dec 2008 21:44:37 GMT

Host

172.16.20.200 255.255.255.0

needs a router to reach

172.16.10.100 255.255.0.0? (Yes|No)

Host

172.16.10.100 255.255.0.0

needs a router to reach

172.16.20.200 255.255.255.0 (Yes|No)

Based on the answer above, you determine which host sees the other host as belonging to its own subnet. This is a broken network to begin with but the question is valid and can be seen as tricky CCNA question 🙂

Edison.

Re: how to check if devices are on same network or not?

royalblues — Wed, 10 Dec 2008 21:45:37 GMT

Best way is to put it to test

Router(config)#int fa 0/0

Router(config-if)#ip add

Router(config-if)#ip address 172.16.10.100 255.255.0.0

Router(config-if)#

Router(config-if)#no sh

Router(config-if)#

Router(config-if)#int fa 0/1

*Mar 1 00:01:06.299: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state t

o up

*Mar 1 00:01:07.299: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthern

et0/0, changed state to up

Router(config-if)#

Router(config-if)#ip add 172.16.20.200 255.255.255.0

% 172.16.20.0 overlaps with FastEthernet0/0

Router(config-if)#

Narayan

Re: how to check if devices are on same network or not?

Edison Ortiz — Wed, 10 Dec 2008 21:48:06 GMT

Narayan,

I think you are missing the point 🙂

Re: how to check if devices are on same network or not?

Jon Marshall — Wed, 10 Dec 2008 21:52:12 GMT

I understand how it works in the respect of 172.16.10.100 255.255.0.0 thinks 172.16.20.200 is on the same network because of it's own subnet mask ie. 255.255 but that wasn't the question or at least it wasn't the way i interpreted it.

The question was is 172.16.10.100/16 on the same network as 172.16.20.200 and not does 172.16.10.100/16 think 172.16.20.200 is on the same subnet.

172.16.10.100/16 = network = 172.16

172.16.20.200/24 = network = 172.16.20

maybe it's a terminology thing in terms of network/subnet.

And maybe it's just me as i seem to be having these sort of dicsussions with a few fellow NetPro's and the one thing they have in common is me !

Perhaps i just need a break 🙂

Jon

Re: how to check if devices are on same network or not?

royalblues — Wed, 10 Dec 2008 21:52:55 GMT

I agree

You were explaining more from a routing perspective whereas i was referring to the configuration on a single router 🙂

Narayan

Re: how to check if devices are on same network or not?

Edison Ortiz — Wed, 10 Dec 2008 22:05:52 GMT

The OP never asked about configuration in a router.

That's the problem with us techies, we just think about if the router supports the commands and we end up failing on those tricky questions during the exam 🙂

I've been burned many times assuming just that and now read the questions differently.

I have a feeling the OP saw this question in a Cisco exam 🙂

Edison.

Re: how to check if devices are on same network or not?

Edison Ortiz — Wed, 10 Dec 2008 22:08:19 GMT

The question was is 172.16.10.100/16 on the same network as 172.16.20.200/24

It is 🙂

The other way around, the host does not see the other host as its own subnet - needs a router 🙂

Re: how to check if devices are on same network or not?

Jon Marshall — Wed, 10 Dec 2008 22:13:40 GMT

okay, you can put it in bold if you like 🙂

"The question was is 172.16.10.100/16 on the same network as 172.16.20.200/24"

It is on the same major network 172.16. but for the life of me i can't see how

172.16 = 172.16.200

From each addresses perspective i can see how 172.16.100.16 thinks 172.16.20.200 is the same network but i didn't think we were talking about perspective.

Forget it, it's me.

Jon

Re: how to check if devices are on same network or not?

Edison Ortiz — Wed, 10 Dec 2008 22:15:04 GMT

Jon, my friend. Step away from the computer 🙂

Seriously, I know how you feel. I've felt burned a couple of times from answering questions in NetPro in addition to holding a full-time job. Take a week or two off. It helps.

We don't have to compete in the 'Top NetPro' of the month anymore 🙂

Re: how to check if devices are on same network or not?

viyuan700 — Wed, 10 Dec 2008 22:26:15 GMT

hi mahesh

your network

172.16.10.100/16

network 172.16.0.0

first host 172.16.0.1

Last host 172.16.255.254

broadcast address 172.16.255.255

next network 172.17.0.0

So your network 172.16.20.200/24 and 172.16.10.100/16 are host 172.16.0.0/16 network