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

Unanswered Question
Dec 10th, 2008

i have one host IP and another host

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

many thanks


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4.5 (2 ratings)
Jon Marshall Wed, 12/10/2008 - 13:10


Not sure i fully understand. is host 10.100 on network 172.16. is a host 200 on network 172.16.20.

is there some connectivity issue you are having.


mahesh18 Wed, 12/10/2008 - 13:20

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

royalblues Wed, 12/10/2008 - 13:30

Yes they are in the same subnet

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

The IP address is a subset of the major subnet above

Time to read some ip addressing


Jon Marshall Wed, 12/10/2008 - 13:35

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 :-)


Edison Ortiz Wed, 12/10/2008 - 13:44


needs a router to reach (Yes|No)


needs a router to reach (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 :)



Jon Marshall Wed, 12/10/2008 - 13:52

I understand how it works in the respect of thinks 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 on the same network as and not does think is on the same subnet. = network = 172.16 = 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 :-)


Edison Ortiz Wed, 12/10/2008 - 14:08

The question was is on the same network as

It is :)

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

Jon Marshall Wed, 12/10/2008 - 14:13

okay, you can put it in bold if you like :)

"The question was is on the same network as"

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 thinks is the same network but i didn't think we were talking about perspective.

Forget it, it's me.


Edison Ortiz Wed, 12/10/2008 - 14:15

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 :)

Jon Marshall Wed, 12/10/2008 - 19:47


Ironically i'm not working at the moment but i take the point, i'm actually busier than when i do work !

Since i have nothing but the highest respect for you i think i'll take your advice and have a week or so off.

"We don't have to compete in the 'Top NetPro' of the month anymore :)"

That used to be fun tho didn't it ?.

Still don't agree with Cisco memebers not being allowed to be on the boards :-)

Thanks Edison.


royalblues Wed, 12/10/2008 - 13:45

Best way is to put it to test

Router(config)#int fa 0/0

Router(config-if)#ip add

Router(config-if)#ip address


Router(config-if)#no sh



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)#ip add

% overlaps with FastEthernet0/0




royalblues Wed, 12/10/2008 - 13:52

I agree

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


Edison Ortiz Wed, 12/10/2008 - 14:05

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 Ortiz Wed, 12/10/2008 - 13:28

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



royalblues Wed, 12/10/2008 - 13:40


I think you put it the reverse way

The address is on the same network as


mahesh18 Wed, 12/10/2008 - 13:41

Hi ediortiz,

can u please explain me in more detail

many thanks


viyuan700 Wed, 12/10/2008 - 14:26

hi mahesh

your network


first host

Last host

broadcast address

next network

So your network and are host network


This Discussion