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Questions tagged [mac]

Not to be confused with mac-address tag, Media Access Control is a sublayer of the OSI data link layer that provides addressing and channel access control mechanisms. It resides between the LLC sublayer and the physical layer.

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What are the MAC layer specifications of IEEE 802.15.1?

I'm a networking newbie. I've come across this question but can't find any to-the-point learning resources for MAC layer specifications of IEEE 802.15.1. How can I understand this?
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Why the ARP packet contains values like “Physical Address length” etc?

From what i know,MAC addresses are made of 48 bits,while IPv4 addresses are 32 bits Why are there these header fields? Are there MAC addresses with more or less 48 bits?
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Is IP an abstraction

If packets "hop" from network device to network device across networks using MAC addresses, resolved by ARP, does this suggest that IP is essentially an abstraction? By abstraction, I mean, the ...
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What actually is EIFS?

There are a couple of things on the Internet about EIFS intervals. One way I've found to help people understand EIFS is the following: When a station receives a corrupted frame, it has no way of ...
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1answer
44 views

What is the use of Phy and MAC chip?

Is it mandatory to have a MAC and PHY chip? Are these two chips within a NIC CARD? As I understand, these two chips are connected using RGMII or SGMII or xaui.
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What happens within a switch when a frame is moved from Device A on Switch 1 to Device B on Switch 2? [duplicate]

This might be a noob question but what happens within a switch (regarding mac tables) when a frame is moved from Device A on Switch 1 to Device B on Switch 2? I'm assuming the 2 switches are connected ...
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1answer
75 views

Changing MAC Address

On learning about MAC addresses i came across U/L bit in the first octet. Further on i learned that MAC address could be spoofed. If U/L bit switches according to MAC address modification , how ...
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1answer
104 views

To what address does ARP reply in the presence of MAC masquerading

The ARP packet has a duplicate of the sender/destination hardware address. Theoretically, you could have a case where a device sent Layer2: From AA:BB:CC:DD:EE:FF To FF:FF:FF:FF:FF:FF Layer3: ARP ...
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1answer
180 views

Does MACsec (IEEE 802.1AE) support multicast / broadcast?

In general, Ethernet supports both multicast and broadcast. However, once you start encrypting the payload, you need a key management. I am wondering if IEEE 802.1AE supports multicast and broadcast? ...
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1answer
137 views

Packet with wrong source MAC address

When I send a UDP packet with wrong source MAC address but with right source IP address, assuming a reply is sent, will I get the reply because I have right source IP address, or I will not get the ...
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2answers
77 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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Run MACsec and VLAN in parallel?

MACsec (IEEE 802.1ae) adds a security tag to an Ethernet frame and encrypts the IEEE 802.1Q field, the EtherType and the payload field. If you want to use VLAN, you need the 802.1Q field to announce ...
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BGP with x2 sessions and x2 L3 VLANs - Please Explain

I am learning about Cisco BGP networking now and came across an interesting situation. In my examples, there was one which suggested that two VLANs were configured on Layer 3 in order to run two BGP ...
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2answers
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Why is RTS/CTS optional for IEEE 802.11?

In wikipedia it is stated: Request to Send (RTS) frame: The RTS and CTS frames provide an optional collision reduction scheme for access points with hidden stations. A station sends a RTS frame as ...
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56 views

Connect to the switch console port, type the keyboard I will get messy code

I follow the Tutorial to connect a switch, use ls *usb* I can find the usb: $ ls *usb* cu.wchusbserial1410 tty.wchusbserial1410 I connect to it: screen tty.wchusbserial1410 9600 but I get the ...
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111 views

How might I test layer2 latency over ethernet without a target IP address? [closed]

Is there a way, via standard ethernet layer2 protocols, to test latency to a device without using it's IP address? Background: I have a fibre "box" provided by my ISP physically connected to my ...
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1answer
186 views

MAC ACL to prevent access to unauthorized computers

My company wanted to prevent rogue PCs from being connected to our network. Network access must be allowed only for our company users and specifically for PCs, Printers.. that are provided by the ...
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MAC address table [duplicate]

I believe this is a very simple question for you, but a interesting one for me, so I hope I don't mind you with my first question here, noob question. We have two switches. SW1 and SW2. First of all:...
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Sending packet through LAN cable to another PC having ip of another network

What happens if, say PC A(192.168.2.2) tries to send a packet to PC B(10.0.2.3) connected through LAN(only 2 computers are connected in this case PC A and PC B) as there is no router or a switch ...
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Cisco Asr1001 not able to receive 2048 macs (arps) in a sub-interface

I´m Brasilian, so excuse me any gramar error. I have a cisco router ASR1001 (IOS XE Version: 03.08.01.S) and I need to connect it to a service provider running BGP ipv4. This service provider gave me ...
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1answer
47 views

How often does it happen that at the Layer 2 (MAC) an error goes undetected?

I know there are certain error detecting and correcting codes added at the Layer 2. However is it still possible to have errors go undetected eve with the addition of these codes? What type of ...
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1answer
74 views

In the MAC acronym what do the words Media, Access and Control refer to independently?

I am not a native English speaker and I know what MAC addresses are and how are they used in networks. However what I do not understand is where this words came from independently. What does Media ...
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213 views

Is the MAC address pool from which Bluetooth, Wi-Fi, GSM cards etc take their addresses from the same address pool as the ethernet MAC address pool?

I know that most wireless communication devices have a MAC address. I wonder if the pool from which their MAC addresses are assigned is the same address pool from which physical Ethernet devices also ...
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Why do we have to connect through a default gateway in a LAN?

I'm a beginner in networking and I'm looking for answers for these questions: Why do we have to connect through a default gateway when we are connected to a LAN and want to connect to another devices ...
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677 views

Minimum frame size in ethernet CSMA/CD

How long sender needs to transmit to capture the channel in Ethernet when we apply CSMA/CD ? I my book , i have read it sender should be transmitting for at least the 2*PT,where PT is end to end ...
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881 views

Understanding MAC table with simulation on packet tracer

i created the following topology using packet tracer to understand how the switch mac table works , at the beginning , i looked at the mac table in the swithc S1 before i send any packet or do any ...
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2answers
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How transparent bridging Wi-Fi with Ethernet works?

The way I understand (two-port) transparent bridging is that the bridge simply forwards packets to another segment on the network. But since the MAC address of the ethernet interface is different to ...
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1answer
79 views

Why is local network communication handled differently to inter-network communication in the OSI model?

Looking at a Stack Overflow question - https://stackoverflow.com/questions/13006949/what-is-the-difference-between-the-data-link-layer-and-link-layer - one of the answers says that the data link layer,...
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3answers
1k views

Count of MAC addresses misunderstanding

I know that MAC address has to be unique. It has 6 elements - k. And it chooses from 36 chars (A-Z,0-9) - n. It means that there are nk combinations. 366= 2176782336 If there are 7.5 billions of ...
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1answer
34 views

Exact trunk operations over an incoming tagged frame

Consider the following example: H1 --- S1 --- S2 --- S3 --- H2 Hx are hosts, Sx are switches. Both hosts are connected with access port on VLAN 20 to the corresponding switches, while all the other ...
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Routing packets in 802.11 (Wi-Fi)

Say we have a router (capable of the 802.11 protocol standards) and some number of devices that are configured to communicate with this router. I have learnt about how devices/nodes use CSMA/CA to ...
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1answer
139 views

Switches - help me to understand please

If a PC wants to send to another PC through a switch and does not know its MAC address, that means all PCs on network will receive it and see it!! If we change the NIC for a PC in the network, how ...
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468 views

NLB Multicast / Source Mac Address

So I've been trying to complete my MCSA, I'm now on 412. Anyway, NLB (network load balancing)... I'm struggling with how it works. Multicast: Each node in the cluster keeps it's own mac and IP ...
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Regarding Encapsulation in OSI layer

The term encapsulation generally signifies the below in terms of OSI model as described clearly here "Each “function” (broadly speaking) encapsulates the layer(s) above it. The network layer ...
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What are the most common technologies that the IPv4 or IPv6 run on top of BESIDES the ethernet protocol?

I recently found out that lots of different types of devices have a MAC address not just ethernet devices. I was thinking that it is possible for Internet protocol to run over many other types of ...
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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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1answer
102 views

MAC Spoof frame delivery

in this topology, when I change MAC address on attacker NIC to PC2s MAC, where is running webserver, then ex. icmp attacker -> PC1, so in switch CAM is on Fa0/3 same MAC as on Fa0/2 I think so...? Now,...
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IPERF TCP vs UDP

I had to determine UDP performance over multi-hop network , I used MAC Air over gigabit ethernet ( Thunderbolt). As is customary, TCP was tested and the gig over link was saturated ~900mbps, but ...
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2answers
300 views

Checking the binding of IP/MAC addresses for a device

As a network administrator, assume I want to check IP/MAC binding of a certain device in my network to check if the binding has been changed or not (Since my network does not have DHCP server and ...
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1answer
925 views

Layer 2 Switch Mac Address

I know a layer 2 switch floods the frame out asking who has a certain mac address. My question is how does it know what mac address to ask for in the first place? Scenario: A brand new switch is ...
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2answers
660 views

How does a router know onwhich switch to send a packet?

Supposing we have a router (Internet box for example) with 2 switch connected on it. We have a machine A on switch 1 and a machine B on switch 2. The router wants to transmit a packet to machine A ...
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1answer
14k views

Assign an IP to a MAC Address to DHCP POOL

The idea is that I want to have a static IP for the MAC computer always assign me the IP . please help , as would the commands ? I have a cisco 3650 switch core where I configured the DHCP and VLAN ...
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1answer
471 views

What is persistent connection and session

There is one thing I still cannot understand is persistent connection and sessions. I will explain how I understand all network stuff. Physical layer . This is just voltage levels going through ...
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1answer
93 views

Host A to Host B on a remote LAN

I'm a newbie to networking. I wanted to ask this: When a transmitting device (host A) wishes to send packets to a host (B) which is on a remote network (LAN), (I understand that the datagrams are ...
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1answer
672 views

How to calculate the data rate in 802.11g? [closed]

I know this is not the community to discuss my homework problem but I cam confused because I cannot find a formula that can find data rate for 802.11g standard given modulation, coding rate and ...
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1answer
1k views

MAC address table showing the same MAC address on one port

When I try the sh mac address-table int gi 1/0/19 command: sh mac address-table int gi 1/0/19 Mac Address Table ------------------------------------------- Vlan Mac Address Type ...
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1answer
60 views

My server can see traffic between other servers

I was troubleshooting one of my servers when I noticed something odd. In the PCAPs I took from my server, I found non-broadcast traffic where my server was neither source or destination. The traffic ...
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1answer
73 views

Detecting MAC addresses in a shared medium using WLAN/802.11 features

Say you have 2 WiFi-enabled devices (e.g. 2 smartphones running a Linux-based OS) A and B, within range of each other, and within range of an access point of some WLAN. Both of them have their Wi-Fi ...
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1answer
202 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 ...