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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37 views

can two devices communicate without physical layer?

can 2 device communicate with each other without data going to physical layer? for example we just use protocol of data link layer that use MAC address , but transferring this frame data between 2 ...
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4answers
2k views

How to detect the presence of a known MAC address on the .local ? (and get IP)

I would like to make a presence detection application which would be able to detect when a known device connects to the local Wifi network. So basically I would know the MAC address of the device, but ...
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I can receive a Ping Reply from a device but not an UDP Broadcast message? [closed]

I have a simple Setup which consists of a Windows PC-Ethernet Switch (10/100M)-Embedded Device. I can ping the Embedded Device, no problem at this stage. The Embedded device is UDP Broadcasting (SRC ...
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6 views

PPP vs PPPOE vs Ethernet frame [duplicate]

PPP is a protocol that encapsulate data for point to point communication between 2 device that know mac address of each other ( I say they are in a scope that can see each other) why we need PPPOE and ...
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1answer
491 views

Distributed Trunking Inconsistent MAC table

I've recently faced a problem in an HPE Distributed-Trunking Switch-to-Switch Square-Topology. Image 1 (shows the essential part of the architecture that consists of 4 switches working in pairs, ...
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2answers
35 views

Is there a layer 2 protocol that can be used to send arbitrary data?

I would like to design several devices that receive simple commands from a single controller device all residing on the same layer 2 switch. Is there a protocol that allows me to do this without ...
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1answer
1k views

Do typical Ethernet switches have timeout for MAC table entries?

Ethernet switches have a learning process through which they gradually begin to understand the network topology -- which MAC address is behind which port. When seeing a port to send a frame with a ...
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1answer
32 views

Do unicast frames get sent to all switches associated with the target VLAN?

If a network topology has a VLAN which spans multiple switches, what happens if a frame is sent to a MAC address that is connected to the source device's "home" switch? By that I mean if a ...
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2answers
53 views

Basic conceptual questions about network interfaces

I have some basic questions as I am trying to understand the concept of network interfaces a bit better. Is network interface same as network interface card (NIC)? If not, what's the difference. What ...
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1answer
44 views

Mac Instability in STP after topology change!

So I'm learning about STP and I recently been taught that when the topology is changed due to direct or indirect Link failure a Mac Instability could occur, So I was wondering, If the blocked port is ...
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1answer
22 views

issue regarding broadcast mac address

I read a line saying {Routes do not forward packets coming from one interface having broadcast mac address (FF:FF:FF:FF:FF:FF)} what is meant by one interface in that line? if router cannot broadcast ...
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2answers
42 views

What is Mac Addressing in terms of Networking

I want to ask what does the term "Mac Addressing " mean ? I know what is a Mac address ,but when we say for example that "one of the functions of Network Interface Card (NIC) is MAC ...
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2answers
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Private IP vs MAC

What I know is that when we connect to another IP, our Public IP gets shared to the outside world, and when they address us they use our Public IP (gateway), and then the gateway directs the ...
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4answers
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Why do we use VLAN?

According to my understanding, the network switch will look out for the specific MAC address and then it will forward the frame so basically it doesn't broadcast the frames then why do we make VLANs? ...
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2answers
968 views

Why does a switch have different MAC addresses?

I am working with Cisco Nexus 3000 switch. I was under the assumption that a switch will always have a single MAC address but when I ran the following command, it displayed two different MAC addresses ...
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2answers
593 views

Does a PC have a MAC address table?

I have a network topology like this: We know switch has MAC address table, but does the PC have MAC address table? I know PC have ARP table in Windows I can use arp -a display all the arp information ...
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2answers
167 views

Basic understanding of network operation

Assume two stations, A and B, are connected by two intermediate routers. A----R1-----R2----B Now, when A sends a packet to B, then the OSI model will come into the picture. Like, A's TCP layer will ...
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2answers
2k views

Confusions regarding byte and bit ordering of Ethernet Frame

I understand the concept of Endianess regarding numbers because there the bit significance is well defined. But when applied to things like Ethernet frame or Mac address, things are so clear to me, ...
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2answers
137 views

Spoofing the L2/L3 information and replication across L2

Could I have a server that spoof the same IP/MAC address of my server on the same L2 network that: 1 - does not do any conflict on the network. 2 - And on the same time when capturing packets on my ...
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3answers
5k views

Why do we need MAC Address if we can uniquely identify each machine with an IP Address

I learnt that in ARP Protocol, to send a packet from one machine to another machine we need to know the MAC Address of the destination machine but since the destination has already been assigned a ...
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2answers
2k views

Strange router's MAC address from ICMP Echo Reply?

Using Wireshark to capture ICMP packets (Windows) using ping to google.com, I can see the source-MACAddr of the ICMP Echo replies is not the same as the MAC address of my direct router (which is the ...
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3answers
42k 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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3answers
6k views

Does Switch need its own MAC address?

I saw a post say Switch do not need its MAC address, unless it's an administrable Switch for managing. but I found the spanning-tree protocol need a MAC address of Switch to form STP Root Bridge ID. ...
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1answer
238 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 ...
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2answers
856 views

Endpoint MAC address change detection [closed]

A question regarding a host behavior when gateway mac address has changed (although it deals with Windows, I think it's the best forum). Assuming a windows host sending trafic to a destination IP, ...
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3answers
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How does a switch learn a switch table?

Say the switch table is empty. If computer A sends a frame destined to computer B, the switch will broadcast asking who has the mac address of B. What if C suddenly sends a frame to A? What is the ...
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1answer
41 views

How does router know MAC addresses of computers that are connected to a separate switch? [duplicate]

i am a newbie but i need to understand this ARP thing. In my company we have a router that has 3 switches connected to it. On the switches there are more than 100 hosts. I know that switch learns and ...
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3answers
8k 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 ...
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2answers
92 views

How does the ARP table know to update if two hosts flop IP addreses?

When hosts on the same local network communicate, they manage their own ARP tables which translate between IP addresses and MAC addresses. Thus when computer A needs to send data to IP address ...
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2answers
397 views

MAC address and unicast, multicast and broadcast

I'm very new to computer networking and I'm trying to figure out this dilemma about the Unicast, Multicast and Broadcast transmissions. I was told that MAC address are unique for each device and they ...
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1answer
48 views

What if receiver changes its IP address during the transmission process?

Suppose I am sending data to a laptop with IP address say x but before data could reach its destination the laptop is moved to another network and now its IP address becomes Y. Will the receiver still ...
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1answer
210 views

Sending a gratuitous ARP on an interval - Cisco

In response to my question Propagating Static MAC Addresses , I realize I can not avoid the unknown unicast problem. Essentially I have hosts that forward their traffic via an L2 frame to a ...
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1answer
29 views

BPDU Header System ID Extension

Previously network switches was using the 8 byte field Bridge Priority to identify a root on the network.When networks grows and becomes complex vlan creation comes into play the 2 bytes Bridge ...
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3answers
62 views

Propagating Static MAC Addresses

I have a situation where I need to place a static MAC on a switch as the server in question does not generate any outbound traffic. This static MAC seems as if it will work for hosts on the same ...
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4answers
2k views

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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1answer
21 views

Huawei switch mac address sticky (model S5720) persistence after power cycle

Suppose I configure the commands "port-security enable, port-security mac-address sticky" in a Huawei switch port, then an endpoint device is connected on the switch port, and a MAC address ...
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3answers
885 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 ...
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2answers
2k views

Same MAC address on different VLANs

I am facing a situation where on the core network I have around 15k MAC addresses, and on the edge switches (Access Layer), I am finding switches with 27k MAC addresses. Access switches are configured ...
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3answers
145 views

Switching and MAC Address representation?

Since the destination and source MAC addresses in a frame in a LAN change, how does it know where to finish, as the destination is only the next hop? And if there is a switch, which connects to hosts ...
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3answers
20k views

Do Bluetooth Devices have MAC address with the same specification as the MAC addresses of the Ethernet and Wi-Fi Network cards?

I recently found out that ZigBee devices have MAC addresses. ZigBee is more related to Bluetooth from what I know rather than Ethernet or Wi-Fi. Do Bluetooth devices such as phones, headphones, ...
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2answers
149 views

Are all packets addressed with the MAC address of the router as they leave the machine?

In the Comptia Network+ All in One, it is said that most home routers have a switch built into them. It is also said that the first thing the router does is strip off any layer two information present ...
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1answer
142 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
101 views

Unicast and Multicast MAC address convention

I need help in understanding how Unicast and Multicast MAC address is differentiated as explained in wiki. According to what I understood, when the least significant bit is set as 0 in the first octet ...
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3answers
91k 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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Why would OpenFlow require N^2 entries for MAC address learning in single table?

I'm reading this whitepaper and trying to wrap my head around why it would require O(N^2) entries for MAC address learning in OpenFlow with single table. See paragraph 2.2.1. In my naive mind, I think ...
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1answer
41 views

Unknown device mac address listed in switch table on start out

After playing a little bit with a topology randomly created in packet tracer, I figured out that the switch (Switch0) stores a unknown device mac address on start out, wich I think that it belongs to ...
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9answers
85k views

Reason for both a MAC and an IP address

If my computer has an IP address,why does it need a MAC address?
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2answers
54 views

Can a host from different subnet bypass the network mask validation of destination host and communicate on layer 2?

I am aware that a host will always check the subnet of the destination node before the transmission in order known if it has to send it to the gatewey for different subnet. However, would it be ...
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3answers
85 views

Forwarding and routing table for host [duplicate]

I'm new to computer networking and from what I've studied, I've understood that Forwarding tables map MAC addresses to ports. So they are used by switches. Routing tables map IP to IP ..they define ...
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2answers
207 views

Why do WiFi bridges replace the source MAC Address with their own?

Ive read quite a bit about the issues i currently have with my Aruba WiFi Bridge 501 and the failure of DHCP going through, and as far as i can tell the issue is that the bridge replaces the MAC of ...

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