Questions tagged [mac-address]

For questions about Media Access Control (MAC) address which is used as the OSI layer-2 address for many OSI layer-2 protocols.

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Switch Lookup Table

I was just reading a book called HeadFirst Networking and I'm a bit confused about something. I am attaching an image from the book. The page says that the direction of the frames as maintained in the ...
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3answers
201 views

Lab: I need to determine information about a device on a specific port of a Cisco multilayer switch

I have a Cisco Catalyst that has a port that is up up, and the device does not show in the ARP table. The MAC address-table shows a MAC address for the port. What can I do from that switch to find out ...
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2answers
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How is Multicast IP mapped to Multicast Mac address?

My main concern is why is the address 01-00-5E- and how? Especially 5 and E??
6
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1answer
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Unable to fetch Mac-Address table via SNMP. Is there a command/setting I need to enable?

I'm using SNMP to poll switches for data. I'm trying to retrieve the MAC address table (sho mac address-table) to view what devices are connected to various ports but I seem to have encountered a ...
6
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2answers
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Cisco IOS: How to view MAC addresses on an Ethernet pseudowire

With two Cisco ME3600 (or similar MPLS & VPLS capable devices) running recent code [15.3(3)S], is it possible to show the MAC addresses passing over a standard MPLS encapsulated xconnect? In the ...
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3answers
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Using SNMP retrieve MAC addresses of directly connected machines to a switch

I want to get MAC address of machines directly connected to a switch using SNMP. I am querying dot1qTpFdbPort for this. But this returns all the MAC addresses learned by switch which includes machines ...
5
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3answers
9k views

How to trace a MAC address on a switched LAN?

How to trace a MAC address on a switched LAN? I want to be able to find out a switch port's MAC address. No device uses IP, therefore no address resolution and no SNMP. No device runs CDP, therefore ...
5
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3answers
45k views

MAC Address cloning. Why and when is it required?

REF: https://superuser.com/questions/932293/motorola-sbg6580-cable-modem-into-bridge-mode-on-bright-house-networks-does-not Question being, with cable based connections where your incoming cable can ...
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2answers
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Does a switch MAC address table sync across all switches in the same VLAN?

Ok, I have read up about this 16K limit for the MAC address table, or better known as the CAM table, on certain switches. Lets say I have 14 different edge switches with that 16K limit, and I have ...
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3answers
1k views

When are MAC addresses used instead of IP addresses in the OSI model?

Okay, so I'm studying for the Network+ exam, and I've gone over the OSI model about a million times, and I understand most of it fairly well, and my studies are coming along fine. However, there is ...
5
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2answers
704 views

Learn MAC addresses via replies to other hosts requests

I have a question regarding ARP: If host A wants to send a message to host B and the ARP table of host A does not contain a MAC address for host B then he sends an ARP request and host B replies with ...
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Did the LSB-first method of transmitting the canonical MAC address in Standard Ethernet have any specific advantages?

When MAC addresses are sent out they are sent such that the Group Address Indicator is the first bit of the Ethernet frame but when stored in memory this forms the LSB of the leftmost byte of the MAC ...
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3answers
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Is there any relation between MAC addresses of a dual band (2.4 and 5 GHz) router?

I have a use case where I need to determine whether two MAC addresses belong to the same router with dual band connection 2.4 GHz and 5 GHz. When I did some study, I found that the MAC address of ...
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3answers
105k views

How to find the MAC address of a router?

I'm trying to figure out the MAC address of my router. This picture is of using the command ipconfig: This picture is of using the arp -a command: I see it says my IPv4 address is 192.168.1.114, so ...
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1answer
2k views

Which switch MAC addresses are used for the Bridge ID in STP?

Lets imagine that I have big LAN environment with many switches and many VLANs, for example, VLANs 5,15 and 50. I have PVST+ activated, and all of my switches have same (STP) priority. I connect a ...
5
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1answer
2k views

Reason for U/L bit in MAC address

What is the reason for U/L bit in MAC address? Or is it solely for identifying if MAC address is locally generated or not and technically it is not used anywhere?
5
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2answers
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Which layer does modem operate and are they still used?

I was searching this for quite long time but I haven't found any satisfying result so my question is basically that, if I understand correctly how modems work and when they are used. I have some more ...
5
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2answers
176 views

does MAC filtering provide security against MAC spoofing in wired networks?

i have googled about mac address spoofing.All I know is that MAC filtering is not much of a protection in wireless network.And in wired network it only works for routers that support MAC Filtering.Is ...
5
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1answer
374 views

Cisco MAC Sticky Ports

So I have setup a sticky port on my switch with 1 allowed MAC for an access point. It has grabbed the Mac of the AP and after testing the port with a pc it shutdown the port as it should. But then I ...
5
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1answer
144 views

What are the various standard and industry practice ways to express a 48-bit MAC address?

My team builds software that allows MAC Addresses as user input. These addresses are often copy and pasted from various platforms in a variety of formats. Wikipedia documents MAC Address Notational ...
5
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1answer
2k views

MAC address can be used to generate an IPv6 link local address

MAC address can be used to generate an IPv6 link local address. What is the process of using MAC address to derive an IPv6 address ? What are the problems that can be caused due to process of using ...
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3answers
476 views

Switch and mac address table

I thought that a switch learnt the mac addresses by the computers sending out packets. However when I configured 2 switches, and 2 pc's, 1 pc connected to 1 switch, the other pc connected to the other ...
4
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2answers
12k views

What does a switch do when the destination MAC address is unknown?

Say I just connected my computer to the internet through a home/office LAN network. I then proceed to ping google.com. Of course, the DNS converts google.com to the destination IP address, but how is ...
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4answers
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Is there a way to get physical location of computer through MAC address?

Is there a way to get physical location of computer through MAC address?, I know switch's address and computer's mac address. All this on a LAN network
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3answers
979 views

What is responsible for dropping Layer 2 frames that's not addressed to it?

It's my understanding that if a network interface card (NIC) receives a Layer 1 packet, it will extract the Layer 2 frame from it, checks its destination MAC address, and if it is not addressed to it (...
4
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3answers
937 views

What is the point of ARP?

I'm a complete beginner at networking, but if I've understood this correctly, the gist of ARP is: We want to use high level adresses to the highest degree possible but ultimately, we actually need ...
4
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2answers
534 views

Learning of MAC addresses with cut-through switching?

I would like to ask, what part of frame is actually read in cut-through mode of switching? I understand that as soon as he read the destination MAC address it can forward. However, how will switch ...
4
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1answer
779 views

Will the Sticky MAC access policy prevent unauthorized hubs from connecting to a network?

We have Meraki MS 250 switches. I have discovered some personal hubs attached to the network and want to ensure these devices wont work on the network to discourage the behavior. From what I can see,...
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1answer
397 views

Can I assign any MAC address in my internal network?

A piece of hardware I am working for contains a small network, which includes about 13 devices. This network is dedicated and only internal available. Due a factory error, a certain type of those ...
4
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1answer
144 views

What MAC, IP and IPv6 addresses should I use as example for testing and documentation?

There are example.com or example.org domains used for documentation. There are MCC 001 and MNC 01 used for testing equipment in cell networks. Are there MAC, IP and IPv6 addresses that are intended ...
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1answer
229 views

How do we prevent loss of sensitive information from MAC spoofing?

While IP addresses are often dynamically assigned during runtime, hardware addresses (so called MAC addresses) are usually statically allotted when a network interface card is manufactured. What ...
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4answers
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ARP table does not store devices responding to a broadcasted ping request

I have got a simple question, I am doing a broadcasted ping request on my local network, using a Mac with the latest Yosemite 10.10.4. So I ping 255.255.255.255, I get responses from a bunch of ...
4
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1answer
1k views

Why would a switch ever send an ARP request for a MAC address when it can just wait for the first packet to be received from a device?

I've been reading 'Windows Networking Fundamentals' and in that book it says that a switch can learn what MAC address is associated with a particular port when the connected device makes its first ...
4
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1answer
83 views

Why switch has records in mac-table when i just set ip address to the hosts which connected to the switch?

I created a new switch and connected to two hosts in GNS3.Like this: Host1--->LS<---Host2, i think the mac-table in the switch should be empty before i sent data between two hosts. But when i just ...
4
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1answer
1k views

How are duplicate packets handled at the Data Link Layer?

Reading up about the data link layer I found that the logical link control sublayer uses sequence numbers to find duplicate packet frame transmissions. I understood the sequence number game with ...
4
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1answer
3k views

MAC Table vs ARP

I understand that for a switch to learn a MAC address, if host A wanted to send data to Host B the switch learns host A MAC and places it in the MAC table. If it doesn't know where the MAC (for Host B)...
4
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1answer
596 views

Dell N3000 - Use port security for certain ports while Dot1x is globally enabled

I have 3 Dell N3048Ps that are going to connect to printers and computers. The computers will be authenticated through dot1x, but the printers need to be authenticated by mac address. Dot1x has been ...
4
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2answers
13k views

Mac address and IP address in physical addressing in Data-Link layer

Framing is done in Data-Link layer. We give physical addresses there. Destination address, source address and MAC. If two PCs in different networks, we try to sent data from one another, we specify ...
4
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2answers
2k views

ARP: how are MAC changes for an IP detected?

Assume a simple IPv4 network where all machines are on the same subnet and share a single switch. If an IP moves to another MAC, how are Layer 3 clients supposed to detect that change? Will a client ...
4
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1answer
5k views

What happens if two hosts with the same MAC address are in the same broadcast domain?

I am aware that situation, where duplicate MAC addresses appear in the same broadcast domain, should never happen. However, if such situation happens, then how will the network work? I think one ...
4
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1answer
4k views

show mac address on aggregated interface - Junos

I am trying to audit which interfaces are plugged to which switchport on our EX3300 switches. The problem is that when using aggregated interface I see only one mac address. wadmin@SIN11-VCsw-48-11&...
4
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1answer
2k views

Cisco Catalyst 2960 X MAC access list

I am using a MAC access list on this switch, so I go about it by first creating the MAC access list: #conf t #mac access-list extended aclname # permit host XXXX.XXXX.XXXX any Then, I tie this list ...
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3answers
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When a datagram moves through a network, do the MAC or IP addresses change?

So there are 4 fields I'm considering. Source/destination of each the MAC address and the IP address. If the datagram is going through a few hosts, which of these values will be changing. From what I ...
4
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1answer
314 views

Juniper EX4300 / MAC limiting SNMP trap

I have the following device and configuration: Model: ex4300-32f Junos: 17.3R3-S3.3 show configuration groups GLOBAL-SNMP { snmp { client-list MANAGERS { 10.8.9.0/28; } community TEST-COMMUNITY ...
4
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2answers
3k views

Wrong dynamic ARP entry - IP Address couldn't pinged

Situation: Our Stacked Switch (two WS-C2960X-48LPS-L - 15.2(2)E3 - 192.168.10.19 - VLAN 10) wont be reachable via ICMP or SNMP by the Cisco Prime Infrastructure (172.16.2.103 - VLAN1[nativ]) and back. ...
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2answers
2k views

What are wifi location scans and auto join scans?

Apple announced at WWDC that they are starting to randomize MAC addresses of location scans and auto join scans in iOS 9, in addition to Unassociated PNO and ePNO scans (see the video around 8:00 for ...
4
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1answer
1k views

VLAN assignment based on mac-address or RADIUS attribute

I'd like to know how to assign someone's client device to a different VLAN based on MAC address of that device.What kind of hardware/software would make this solution possible (if possible at all)? ...
4
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1answer
6k views

authentication mac-move permit

Why would someone use authentication mac-move permit when dot1x authentication is not performed by the switch? Note that there are APs attached to the switch, which are being authenticated by a WLC.
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2answers
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Why the first octet of a MAC address always end with a binary 0?

I stumbled upon a piece of code on GitHub: https://github.com/adeverteuil/bash-ula-generator/blob/master/gen-ula.sh # Generate an EUI64 from the MAC address # as described in RFC 3513 # https://tools....
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4answers
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How does a router know the destination mac?

so if I send a packet from a host to another from the same network we know the mac address of both the source and destination. However if the receiver is in a remote network the destination mac ...

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