Comments for What's the difference between a Mac Address and an IP Address?

Comment from Steve on 2009-10-08

2009-10-09T01:49:31Z

Please be clear...we are trying to trace an e mail...we have an IP...probably a public access point...now we want to try to find the mAC address of the computer that sent that mail from that public connection??? Is it possible? Does the router retain that address? This access point was used to access a hushmail account and that account send the mail we are interested in tracing.

The router sees too many MAC addresses to remember them all. I suppose some routers could be keeping a log, but in general they do not.

09-Oct-2009

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Comment from Abhishek on 2009-10-05

2009-10-06T06:52:24Z

Dear Leo,
this information is really very valuable.
I have a keen interest in network security methods in current times and I wanted to ask something to clarify some things for myself ...

I have a system that connects to a router which further connects to my modem.
when i do ipconfig/all, i get the mac address of my ethernet port, not the router or modem, which i can check using the interface for the respective device. if my understanding is correct, my mac address does not go past the router, coz it changes there to the address of the router which further changes to the address of the modem and so on ...
however, at the site "http://www.ipaddresslocation.org/find-mac-address.php" it uses java to find the mac address of my ethernet card.

this is what brings me to my question... as you said, "So your MAC address doesn't make it out very far. Even if someone knows your MAC address, that knowledge certainly doesn't help anyone do anything either good or bad." just as the site used java to find my original mac address, can't a similar process be applied to trace a person/machine's location on the internet.
also, there are proxy service providers, both free and paid softwares, that change the external ip address of a machine. in theory, is ip address tracking the only professional way of tracing a person/machine's original address?
my understanding is that the sender's ip is included in the chat/email/post that is received at the other end, and these proxy servers/softwares change that header info to keep it anonymous. i know legal intervention is required, but is the packet info that contains the IP address the only way of tracing the origin or does it also have mac address info of the originating machine/person?
Please help me understand this better.
Thanks in advance.
Best Regards.

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Comment from sachin on 2009-09-04

2009-09-05T06:56:46Z

I think that mac address & ip addrss is same but from this i know the difference. Nice to share this info. I usually found one site to find the ip address from http://www.ip-details.com/ to get the ip address.

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Comment from shubham on 2009-08-21

2009-08-21T17:07:22Z

Dear sir,
The ip address at any given time in the internet is unique to a host. if so then why is mac address even required?
can't ip address be used to recognise the host inside the network too?

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Comment from Jason Scully on 2009-07-23

2009-07-23T12:20:04Z

For how long the MAC Address remains stored in the router's memory?

Depends on the router, and how busy it is.

- Leo
23-Jul-2009

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Comment from DINESH on 2009-04-28

2009-04-29T06:44:19Z

why cant we replace IP system by MAC system, bcoz MAC address is going to be unique as similar to IP Address instead of sending source IP address we can transmit Source MAC address, why cann't we do that? i am also not clear "MAC Adress travels no further than the next router or equivalent network interface" !!!!

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A comment on: What's the difference between a Mac Address and an IP Address?

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Comment from Jetrue Hudson on 2009-01-15

2009-01-15T22:42:40Z

Dear Leo
Can you connect Macs and PC's to the same server?
How?
Thanks,Jetrue

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A comment on: What's the difference between a Mac Address and an IP Address?

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Comment from Octavius on 2008-12-08

2008-12-09T03:20:59Z

Dear Sir,

This is indeed a useful site.

Please advise me the followings:
Is it mandantory to get a MAC address (OUI/IAB),
even if, I used the ethernet device on a LAN only?

Thank you.

Regards,
Octavius

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Comment from Jason on 2008-10-13

2008-10-13T19:18:46Z

Why would someone want the same mac address as me? I just found out through my Internet provider that some one else had the same mac address as me, which is why my internet wasn't working. How does that happen, and should I be concerned?

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Comment from Dave on 2008-09-05

2008-09-05T22:14:14Z

Would love to know the answer to this above post as well.

IP and MAC - Very nicely differentiated.
I have some doubts. Will the MAC address also go with the IP address as part of the Header details along with the Mail exchange ? Can the Mail be tracked back to the MAC no (ie., the Mail originating PC )?
What is the real purpose MAC Address ?

A MAC address uniquely identifies every network interface. It travels no further than the next router or equivalent network interface. It does not appear in email headers as it makes no real sense to be there.
-Leo

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Comment from Chuck on 2008-08-08

2008-08-08T16:03:44Z

Very interesting in fact I understood your metaphor. Perhaps you can answer a question.
I'm installing a new machine, I'm connected to the internet but cannot open my browser (page cannot be displayed). Checking my IP address it appears as all letters.

Any help will be greatly appreciated

Uh, no. An IP address should never appear as all letters. (OK, an IPv4 address should never appear as all letters, the newer IPv6 is another matter, but not something you should be seeing anyway.) I'd have to know exactly how you're looking at your IP address to know what it is you're actually seeing.

-Leo

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Comment from rahman on 2008-08-03

2008-08-04T05:51:29Z

Dear Sir Leo:

Hope you will fine and healthy. I'm so happy from your site and your information to take us and u solve our problems.
Sir i have Three quetions.
1. what is diffrent between Table and Query in Access programm?

2. What is different between routing protocols and routed protocols?

3. What is different between ISA server and Proxy server?

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Comment from Chandra Sekaran K on 2008-08-03

2008-08-03T11:08:53Z

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Comment from Chandra Sekaran K on 2008-08-03

2008-08-03T10:39:17Z

It gives a good picture about the IP and MAC addresses.
Does the MAC address also go along with the IP address as hidden-part of the Header Details of the Email to the receiving PC / Server ?

No. The mac address only travels as far as the next piece of networking equipment in the path. So it probably only goes as far as your router.

-Leo

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Comment from JohnE on 2008-07-30

2008-07-30T09:49:59Z

Leo - one part of the original question asks about the difference between IP addresses you get 'for free' and those you buy. I think this is asking about the difference between a dynamic and a static IP address - most ISPs will give you a dynamic IP address as standard but will charge you for a fixed IP address; a dynamic IP address is fine if you just use email and the internet, but if, for example, you want to run your own web server, and host it yourself on your own computer, you need a static IP address.

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Comment from Ken B on 2008-07-25

2008-07-25T16:11:49Z

It's funny you use a postal metaphor here. My father once asked me how his computer "knows" how to talk to a computer across the country. I used a postal metaphor to describe how Internet traffic is routed.

When you mail a letter, how does the letter "know" how to get across the country? It doesn't have to. The postman who picks up the mail only has to know how to get it from your mailbox to the local post office. Someone at the local post office only has to know that a letter going to Florida gets sent to the White Plains post office. From there, someone only has to know that it goes to the New York City branch. From there, someone sends it on a truck to Miami. From there, it's put on a truck to the local post office. And from there, it's put on a truck to be delivered.

At each step, all that's needed to be known is which direction to send it on its next step along the way.

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A comment on: What's the difference between a Mac Address and an IP Address?

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