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Ping gets 2 addresses

Posted on 2014-02-14
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Last Modified: 2014-02-17
When  I ping an address in my local network, I get responses from 2 different IP addresses. What would cause this?
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Question by:tenchulyo
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by:Justin Yeung
ID: 39859538
do you have multiple names under your DNS on the same ip address?

or it is a domain root?
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by:tenchulyo
ID: 39859578
Sorry, I'm just a dumb programmer...LOL...can you elaborate on that...Thanks Again!
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by:Fred Marshall
ID: 39859579
Is it possible that one device has two IP addresses assigned to the same NIC?
I've not tried pinging one set up that way it but it seems possible for this to happen if you did.
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by:tenchulyo
ID: 39859589
So you're saying it is possible to add multiple IP's to a MAC on a DHCP, wouldn't that cause IP conflict?
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by:Justin Yeung
ID: 39859601
as you said "ping an address", are you ping IP or Name?
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by:tenchulyo
ID: 39859605
an address 192.168.4.113
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by:Fred Marshall
ID: 39859619
No it doesn't cause a conflict.
Level 2 switches will indeed work using MAC addresses but the MAC addresses have to be translated from the IP addresses.
So, the ARP table should show two IP addresses, each with the same MAC address.
Either IP address will work that way.

Conflicts arise when the same address belongs to two separate devices because then there's an issue of "where to go?"
There's no conflict when the same device has two addresses because there is no question of "where to go?"
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by:Justin Yeung
ID: 39859628
you can have multiple IP address on a single network adapter without problem.

you can add an alternate ip address on a windows box.
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by:tenchulyo
ID: 39859633
Well, not sure if this helps but when I do a arp -a it says "no ARP entries found"
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by:Justin Yeung
ID: 39859647
do you have a management layer 2 switch that connected the device?
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by:Fred Marshall
ID: 39859663
Sometimes one needs to ping in order to refresh the arp cache.
I would ping both addresses and then follow shortly with arp -a
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Author Comment

by:tenchulyo
ID: 39859680
The switch it is connected to directly is Unmanaged (Netgear Prosafe), I can go check the trail to see all switches that are involved in the connection...the PC I'm pinging from is in another site.
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by:Justin Yeung
ID: 39859694
fmarshall,

you might not able to see that in a windows machine, and he doesn't have a managed switch to troubleshoot.

tenchulyo,

is the target machine a windows box?

if it is, check if you have 2 IP assigned on the machine.
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Expert Comment

by:Sasa Kranjac
ID: 39859717
A high level overview:

A name, for example www on microsoft.com, or www on google.com domains can have multiple entries in DNS. Pinging either www.microsoft.com or www.google.com would return different IP addresses.
Try to run nslookup.exe at a command prompt and type either www.microsoft.com or www.google.com. As the result you will get multiple IP addresses.

It is also possible to set up a single network card in Windows (Server or Client) with multiple IP adresses, even from different subnets. That way you can access computers from different subnets.
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by:Fred Marshall
ID: 39859721
fmarshall,

you might not able to see that in a windows machine

I'm not sure what was meant by "see" or "that"....???

In Windows XP:
Network Connections
Local Area Connection ... (or?)
Internet Protocol (TCP/IP) Properties
Advanced TCP/IP Settings
IP Address <<< window will show all the IP addresses assigned.

Windows 7 is the same....

So, in this context, one is able to see that in a Windows machine.
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by:Justin Yeung
ID: 39859724
sorry I meant the arp info even after you ping the ip
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by:Justin Yeung
ID: 39859730
or there are 2 adapters "wired and wireless", so then you got 2 ip from the dhcp server on the same dns name
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Author Comment

by:tenchulyo
ID: 39859738
fmarshall,

I went into the machine and everything says obtain automatic (IP & DNS)
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Author Comment

by:tenchulyo
ID: 39859743
Also, this machine has no wireless only 1 NIC
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by:Fred Marshall
ID: 39859823
Well, maybe you could use Wireshark on the pinging computer to see what MAC addresses come back with the pings..... something like that.
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by:Justin Yeung
ID: 39859881
can you put the ping result on here?
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by:tenchulyo
ID: 39859912
Ping
Sure...Here it is.
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by:Justin Yeung
ID: 39859922
are you pinging from the machine that has 192.168.4.113?
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Author Comment

by:tenchulyo
ID: 39859927
where should I ping to from 192.168.4.113
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by:Fred Marshall
ID: 39859931
now, after the ping, will arp -a show the MAC address?
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by:Justin Yeung
ID: 39859933
it should if you have a management switch..........not sure it will show up on a windows machine.
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by:tenchulyo
ID: 39859938
192.168.0.242 is the machine I'm on locally

192.168.0.126 is the mystery machine
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by:Justin Yeung
ID: 39859946
if you ping 192.168.0.126 since it is on the same subnet......

then do a arp -a on the machine of 192.168.0.242

if you can see the mac address of the mystery
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by:tenchulyo
ID: 39859977
ARP -a

Here are the ARP results For the sake of security I blacked out the last 2 sections
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by:Justin Yeung
ID: 39860013
what is your dhcp server? hardware or software?
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by:Darr247
ID: 39860036
I suspect there's a VPN present that we haven't been told about, and proxy-ARP is making the connection[s] happen for the pings.
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Author Comment

by:tenchulyo
ID: 39860048
Well, it's windows driven, if that is what you are asking...not using the router's software.
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by:Justin Yeung
ID: 39860058
you have a unmanaged switch. so I believe you only have one subnet on your local network.

the .4.x address is not on the same network. it could be a VPN connection as mentioned by Darr247
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Author Comment

by:tenchulyo
ID: 39860085
Well I do believe there are more than 2 sub nets. .14.x and .9.x also exist. The VPN I know exists is to a vendor we contract, but their IP's begin with 10.1.100.X they host a huge application. Does this clarify things more... We use sonicwalls to connect the sites. Sorry, I'm trying to be as detailed as possible.
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by:Justin Yeung
ID: 39860111
you have a unmanaged switch but using 2 subnets? how does it route your traffic?

would you please provide more detail on your network diagram.
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Author Comment

by:tenchulyo
ID: 39860115
Like I said, I'm the programmer...the reason I'm here is to try and be proactive because the IT dept can't figure out the problem and it is making my application respond incorrectly. I know the app works perfectly, I've tried it in virtual networks and other sites without any issues.
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Accepted Solution

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Justin Yeung earned 500 total points
ID: 39860117
this is probably your problem, you have a unmanaged switch with multiple network on it....

http://answers.yahoo.com/question/index?qid=20070828235104AA8NYiT
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Expert Comment

by:Fred Marshall
ID: 39860305
what do you get if you do this command:

tracert 192.168.4.113

?
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by:tenchulyo
ID: 39860542
YES Justinyeung!!!

You got it! Now, It says I can setup a vlan to correct the issue. The switch does support vlan,
however, i am not familiar with this technology... how do I set this up on a netgear plus prosafe (GS105E). Any ideas?
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Author Comment

by:tenchulyo
ID: 39865107
Nevermind...just taught myself everything over the weekend and fixed my issue...thanks to all!
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