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What is the MAC address of the broadcast frame? i have no idea and need help

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posted on Jan, 26 2012 @ 11:54 PM
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if anyone can explain this too me that would be great I'm taking online classes and if i could get a damn tutor it would be great . My teacher posted a response to my answer then explained how a default mask worked i under stand every thing he said except for the damn question. here is his response to my answer

professor

Great. The mask enables TCP/IP devices to differentiate between the network portion of the address and the host portion of the address. The mask acts like a filter that is used to determine the address of the network. It relies on a simple logical bit ANDing operation. The logical AND basically states that if the bits in both the network address and the subnet address are ON, the outcome is ON; however, if this logical operation is not true, the outcome is 0.

I am assuming you know how to translate from decimal to binary. If not, please go over the lecture slides.
For example, you have IP address 100.100.100.100 with a subnet mask of 255.255.255.0, the network device will turn the ip address and the mask into binary:

IP address : 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0
Subnet Mask : 1 1 1 1 1 1 1 1. 1 1 1 1 1 1 1 1. 1 1 1 1 1 1 1 1. 0 0 0 0 0 0 0 0
=========================================================
Network Address : 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0. 0 0 0 0 0 0 0 0

Turn it back into decimal. 100.100.100.0

The Host address is the address of the host on that network. Which is the bits that are not masked. I have the bits in bold above.


Picture this as a home address in a zip code. You could have multiple 1010 Mountain Avenues, what makes those addresses unique is the zip code. The network is the zip code, the home address is the host address.

The broadcast address is the address that is intended to be sent to all devices on the network. It's like the overhead paging system, all devices in the network (layer 3 broadcast domain) will receive the broadcast packet. Switches forward the broadcast frame to all devices on the network. The broadcast address is differentiated by all host bits ON. In our example above, the broadcast address would be: 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0. 0 1 1 0 0 1 0 0. 1 1 1 1 1 1 1 1 or 100.100.100.255

The host bits are can be all ON (broadcast) or all OFF (network address). Those 2 iterations of bits formation are reserved for network and broadcast. When we calculate the number of hosts that you can have on the network, we determine this number by using the formula 2^n - 2. The 2 addresses that are deducted are the broadcast address and network address.

What is the MAC address of the broadcast frame?




posted on Jan, 27 2012 @ 12:04 AM
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Wish i could help you.I was on a personalization ip address site the other day and they nabbed me and kicked me off...wtf.



posted on Jan, 27 2012 @ 12:16 AM
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in my networking 101..i remember that mac-addresses,layer 2 have a broadcast frame of ..

Unicast packets are delivered to a specific recipient on an Ethernet or IEEE 802.3 subnet by setting a specific layer 2 MAC address on the Ethernet packet address. Broadcast packets make use of a broadcast MAC address (FF:FF:FF:FF:FF:FF), which includes setting the broadcast/multicast bit in the address.


source : wiki

just my two cents..


mac addresses are split in two, the vendor part and the specific haedware device id part..each vendor is given a range but for the broadcast mac.. it has to carry an industry tag to broadcast on the network..hence the FF:FF:FF



posted on Jan, 27 2012 @ 12:17 AM
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Your MAC address is like a serial number for individual hardware.

It is used a lot on things like bluetooth, 802.x, etc.

You may have several devices connecting through a network node with identical IP address's (eg coming from the same PC/mobo), the MAC address allows the system to route the data to the right device.*note - Think of a webcam connecting to a live feed - the IP will point to the PC....the MAC address will point to the actual webcam.
edit on 27/1/2012 by OccamAssassin because: (no reason given)



posted on Jan, 27 2012 @ 12:21 AM
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FF:FF:FF:FF:FF:FF



posted on Jan, 27 2012 @ 12:30 AM
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First of all: WTF? What does this even have to do with a MAC address? The MAC (Media Access Control) addresss is a unique identifier burned into a chip on a piece of hardware. It has absolutely nothing to do with subnetting nor IP addressing.

Secondly: Sorry. I've been doing networking for years--all of it in the nature of hands-on, practical experience. I have NEVER understood subnetting, even though I have seen it explained at least a bazillion times. Well, not really a bazillion--more like a jillion. Every single time I have to deal with it I have to use past experience and trial-and-error. Because my brain simply will not absorb its purpose and meaning. I know what "AND"-ing is; I can easily translate from binary to decimal to hexadecimal--but I cannot on my best day understand what subnetting is.

So I guess I'll stand by with you and wait for someone to come along and try once again to explain it in simple terms. Maybe this time I'll get it....

ETA: Well, I already see that I had the wrong idea about MAC addresses. Others answered that question while I was still typing my response, obviously. But I'm still in the dark as far as subnetting.
edit on 1/27/2012 by Ex_CT2 because: (no reason given)



posted on Jan, 27 2012 @ 12:43 AM
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reply to post by pcrobotwolf
 


thanks you guys for answering my post



posted on Jan, 27 2012 @ 02:25 AM
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Originally posted by staple
FF:FF:FF:FF:FF:FF


He answered your question. The text was just going over logical ANDs, the question is just kind of out of place which is why it seemed so confusing.



posted on Jan, 27 2012 @ 09:08 AM
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I have seen this MAC address in packet captures for work, and it really doesnt have a lot to do with the OP, because this MAC address is used by the gateway or whatever device to announce something. This is universal and does not have much to do with subnetting or ip addresses.


In Ethernet networks, a frame that has a hexadecimal MAC address of FF-FF-FF-FF-FF-FF. This hexadecimal address is equivalent to 48 binary “ones.” The meaning of this address in Ethernet is simply that this frame is intended to be received and processed by every node on the network of computers. Broadcast frames are generated when certain network services need to make announcements to other hosts on the network. Too many broadcast frames on a network can degrade communication between nodes on the network.


Source

When you start talking about mac addresses at this level, it is typically referring to ARP, sort of like how DNS resolves google.com to 74.125.113.99, arp resolves the IP to the mac 192.168.1.2 is 00:08:5d:22:2a.

The easiest way I have been able to figure out subnetting, which im not totally sure I have wrapped my head around it even though I work for a ISP / carrier is::

ex: 255.255.255.0

Entire network your local network

Which tells your computer / device where it needs to route the packets, shows the limits of your section of the network, shows us the gateway, and limits broadcast packets. Where 255.255.255 will be always be the same on your side of the network and represents outside addresses, and the 0 is the changable addreses.

Basically you are taking the bigger (entire network) and dividing it up for routing and broadcast purposes.

Here is a subnet cheat sheet that has inverse masks on it, which can be useful when dealing with cisco / adtran / carrier related networking things.

Hope this helps, please correct me if im wrong, because I am certainly no expert and im working towards my cisco certs aswell.


edit on 27-1-2012 by sicksonezer0 because: (no reason given)



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