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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19 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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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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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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1answer
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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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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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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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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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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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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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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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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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Filter Packet PPPoE Discovery

i have a sw nexus i have a router BGN with vlan 50 is going to sw then mode access to Client 1 and Client 2 BNG ==== SW1 == PORT1 =Client 1 (Mode access vlan 50) PORT2 =Client 2 (...
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Multiple mac adrress on one cisco switch interface

How can i config Multiple mac address on one cisco switch interface? (I have 3 laptops and i connect only one laptop every time(I switch between them), and i want to config only one interface with the ...
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How to block unknown MAC addresses in OpnSense

I'm dealing with an OPNSense router, at the moment I already configured the DHCP server to provide IPv4 addresses only to a legitimate list of fixed MAC addresses and I want to block every unknown MAC,...
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decoupling of network and link layer addresses

can you pls help me understand what the instructor is trying to convey in the following slide. from what I understand:- network address and link address are independent in the protocol layers but ...
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How do hosts subscribe to multicast addresses?

So I am having a hard time finding materials online that explains how multicast address are set. I understand what unicast is: Basically one to one communication. In this scenario, an address ...
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Will the switch itself interfaces store in the MAC address table?

I have a topology like this: the port and mac address map: Mac address Interface ----------- --------- aa:aa:aa:aa:aa:aa - pc1 bb:bb:bb:bb:bb:bb - pc2 cc:cc:cc:cc:cc:cc - sw1_ac dd:...
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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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Why can't we assign MAC addresses on our own?

Mac addresses are used in networks, not in internetworks. So, why to not create a protocol, that will automatically assign to connected devices MAC address in that way, so they don't repeat in network?...
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What is the least possible separation of two NICs with the same MAC address?

Suppose you have two NICs with the same MAC address, but not necessarily the same IP address. What is the least possible separation (in terms of number of switches, routers, different IP subnets etc.) ...
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42 views

How do hosts filter broadcast signals in wireless network?

In bus/hub network, hosts check the destination address of every broadcasted packet they receive and accept it if they are the destination, otherwise they ignore it. Do we use the same principle in ...
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1answer
48 views

2 machines can have the same link-local address, in the correct context. What context?

I don't get in what context multiple interfaces/machines can have the same link-local address. Thanks in advance.
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Is it possible to access 127.0.0.xxx in anyway [closed]

So I've been configuring my network at work. We've got a lot of devices from NAS servers to Dante AoIP devices. While configuring some of my devices I managed to set the IP adress of one device to ...
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Is an IP address necessary for a gateway?

When a IP sends something to another host outside the same subnet, it constructs a packet (L3) with the target IP being the IP of the target host, but the frame (L2) has the destination address = ...
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205 views

Why is default gateway in routers configuration usually set as an IP address?

I mean why not just: a MAC address? It should eliminate the need in ARP requests asking for gateway address. Also it should eliminate the need in changing IP addresses in settings when gateway IP is ...
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What allows Pulse Secure to prefix MAC Addresses used for DHCP proxying with 55:4E?

I've been looking at traffic logs generated by a Pulse Secure appliance (formerly Juniper Pulse Secure) and have noticed that when the appliance generates a MAC Address it prefixes that address with ...
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2answers
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How to discover a host when you don't know its mac, ip and subnet?

I have a network switch and I don't know its ip nor mac address nor even subnet. I need to get all this information. Yes, there are tools like nmap and arp-scan, but the problem is they all need an ...
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73 views

How to determine BSSID from MAC Address

As I know BSSID is derived from MAC Address, but I have no idea how it is derived and what pattern is used. Since there might be multiple BSSIDs from a device, I want to get all the BSSID that could ...
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1answer
53 views

How to extract destination MAC from PCAP? [closed]

I have PCAPs collected at the Raspberry Pi (from this paper). I want to extract the following headers: Ether header (3) IP header (12) TCP header (10) UDP header (4) Then convert the PCAP into csv....
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153 views

How to get IP address of device from its MAC address on network?

Though it seems possible duplicate of this question. But the need to ask this question again is to simplify the scenario and the demands to just finding the IP address of the device. The network in ...
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1answer
246 views

Understanding EUI-64

I was reading Forouzan's book. It says following: In IPv4 addressing, there is not a specific relation between the hostid (at the IP level) and link-layer address (at the data-link layer) because ...
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1answer
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152 bit hardware address in dhcp binding?

When listing MAC addresses on a Cisco ISR DHCP service, I get a long list of hardware addresses, one per IP address, but for one IP I get an address so long it runs onto three lines. The other ...
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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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How data travel from a node to a destination IP address? [duplicate]

Let's say I have a lot of devices which connect to a single switch, and the switch itself connects to a router which provide Internet connection. Whenever an application on a node needs to ...
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99 views

Does a router send its own mac address or the mac address of the user?

When a request is made, does the router send its own mac address or the mac address of its user? Does it send the mac address at all? My specific case is the following: I am getting a 4g sim card to ...
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1answer
87 views

Is it possible to propagate MAC address back to sender?

Let me first to tell me what I know, please correct me if I am wrong. I know when Ethernet frame travels across the internet then Layer 3 data (Source and Destination IP) remains same and Layer 2 ...
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2answers
303 views

Cisco Nexus 6k mac move detection not working

My device is cisco Nexus 6001 Chassis (one unit dc switch) # show version ... kickstart: version 7.2(1)N1(1) system: version 7.2(1)N1(1) ... I've configured mac move detection: # conf t # mac ...
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Broadcast Timer [duplicate]

This question is regarding in the process of L2 MAC Address learning. As we know, if a sender sends a packet to some receiver host which switch doesn't know, it will broadcast for learning. Assume an ...
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283 views

Different MAC addresses [closed]

What happens if a host on the network receives an IP packet with a MAC source address that differs from the MAC address in the local ARP table for that source IP. The ARP table entry for that IP was ...
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1answer
2k views

What happens when a switch receives a packet with an unknown source MAC address?

The CAM table cannot be populated with the source address so other action must be taken. Is the switch going to drop the packet?
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4answers
188 views

How can I search for MAC addresses on local network without referencing any IP addresses [closed]

I think there is an IoT device on my network that has lost its IP address or IP address has been corrupted by a power surge. I want to scan MAC address to see if it is still 'hiding' on my network. I ...
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1answer
45 views

Is destination MAC address is always end point MAC address? [duplicate]

To simplify if the destination is on a separate network would the source still does ARP request or does it uses default GW's MAC as destination MAC?
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1answer
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Is this possible (NAT??)

I have a device on another network, say it's IP is 10.1.1.1 I want to ping it from my own network, say host 192.168.1.1, but I want to ping an address in my local segment to do so,so 192.168.1.2. Is ...
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839 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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1answer
132 views

ARP table updated when receive message

I'm studying networking and I have a question about when an ARP table should update. Consider this scenario: Host A has the MAC address of host B in its ARP table. Host B's ARP table is empty. ...
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1answer
134 views

ARP behaviors between hosts connected via switches

In a scenario like the following, where different hosts are connected via switches only, I'm not sure how the ARP packets will look like when A wants to send an IP packet to B. I assumed all the ...
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1answer
386 views

Setting Destination MAC address for RTP/UDP packets

I have a requirement where I have to send the UDP packet to a destination multicast IPv6 address. In addition to that the packets must also have corresponding destination multicast MAC address set. I ...
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1answer
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Finding MAC address with OUI List

I'm in the process of labeling the interfaces of my Cisco 3750G with descriptions referencing the device type that is associated with that port. I understand that I am able to run a show mac address-...
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71 views

Getting the IP Address from a device

I got some kind of "router" from another department and they want to know the IP address. I connected it for "testing" purpose on the switch at our place. I know the switch and port its connected to ...
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781 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 ...

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