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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503 views

Understanding multicast destination mac addresses

I'm currently learning about how to convert between a multicast ip address and the destination mac address. I fully understand the terminology, how to do the conversion, and why the 23 bits, instead ...
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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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Are IP source and destination fields necessary on LAN?

When sending a packet from one computer to another over LAN, you send both an ethernet header and an IP header. The ethernet header has a source and designation MAC address, and the IP header has ...
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1answer
1k views

Juniper ARP table max limit

I'm running EX3300-48T - Junos-12.3R11.2. After binding multiple /24s on multiple vlans on the same switch, Started to notice that the newly and the old assigned IPs are not pinging on multiple ...
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3answers
198 views

How does my network interface know which destination IP to ask for in an ARP request packet?

On my VMware internal nat network, when I try to do a simple HTTP request from my guest to my host OS, the arp request from my guest os asks for the MAC address of my host IP and attach it in the ...
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596 views

Are ARP replies sent directly to the solicitor? [closed]

I understand that most ARP requests are broadcasted to the entire network. What about ARP replies?Are they sent directly to the host asking for the answer? Or must ARP replies go through the router ...
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1answer
346 views

Why do we need VLAN tagging when there's already MAC address table to refer to

Why do we need VLAN tagging when there's already MAC address table to refer to? Switch A VLAN 10 -> Switch B VLAN 10
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3answers
108k 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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3answers
5k views

Source MAC address across VPN

I have multiple sites, all connected centrally to a corporate office over VPN. I can see the IP addresses of the remote hosts but the MAC gets stripped. Is there a way to configure the network so ...
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2answers
3k 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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1answer
1k views

mac access management with fortigate 90d

I'm not very familiar with firewalls. I have a "fortigate 90d". I must simply prohibit access to the internet (via wired network) to a group of about twenty pc. This ban must be made by mac address of ...
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740 views

Does modem has unique MAC address on your home network? [closed]

I know that MAC address is a physical address attached to Network Interface Card(NIC) to identify your computer uniquely. However, MAC address of Ethernet NIC or Wireless 802.11a/b/g/n WiFi NIC are ...
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1answer
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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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3answers
3k views

How does access point changing populate MAC addresses in switch tables?

Let us assume that I have a large corporate WLAN network with many access points having the same SSID. The WLAN access points are connected to each other by learning Ethernet switches. Now, each ...
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2answers
3k views

Multicast ARP Switch

So a few questions that I've struggled to find firm answers on. 1: Does multicast use arp? So does it ask for a corresponding IP address? I think the answer is no, as it translates the IP to a MAC ...
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720 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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1answer
131 views

Regarding the port security violation mode protected, what action needs to be taken when a new device replaces an old device?

If I turn on port security and configure a port with the following; the violation mode to protected, the ageing time to 10 minutes, maximum number of mac addresses to 1. If in the future I replace ...
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1answer
2k views

Is mac address aging just for dynamic/sticky mac addresses?

Regarding Cisco port-security. Is mac address aging just for dynamic/sticky mac addresses? Does the ageing play any part in a statically configured mac address? If no static or sticky configuration ...
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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 ...
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1answer
758 views

What protocol forces a switch to populate it's CAM table with the MAC address of a directly connected switchport?

In Cisco packet tracer, when I connect 2 switches together, the CAM table on each switch gives the MAC address of the switch port of the other switch. This is surprising to me, and it really threw ...
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0answers
3k views

Regarding vPC Dual Active or Split Brain scenario

Consider the below topology: Imagine that both the vPC peer keepalive link and vPC peer link have gone down. I am trying to understand how will that lead to unpredictable traffic flows or loops. ...
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2answers
1k 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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969 views

Can the source mac address in an Ethernet header be used to identify the sender?

I have programmed raw socket programs in C/C++ to initiate small tasks such as TCP/IP 3-way-handshakes, UDP, RTMP, etc. However I became curious about the next layer below IP and I was looking at an ...
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1answer
3k views

Why the FF:FE in EUI-64?

EUI-64 IPv6 addresses are generated from MAC addresses by taking the network prefix (64 bits) and appending the first half of the MAC address, then FF:FE, then the second half of the MAC. Is there a ...
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1answer
589 views

MAC Spoofing and EUI-64

I have two questions that both assume an attacker who has my MAC address: Suppose an attacker connects to the Internet before me, spoofing my MAC. I then connect and tell people to connect to my EUI-...
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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 ...
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1answer
72 views

How do computers connected to a Wi-Fi network communicate within the same network?

Let us assume Host A wants to contact Host B. Does it send the packet addressing (IP address of the Host B) and MAC address of router, or does it use ARP to send to the MAC address of the Host B?
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1k views

Single out switchports with multiple MAC addreses

Finding out how many devices are connected to a single switchport is easy on a non-stacked Cisco network switch with a sh mac add ta or sh mac add int fa/gi/eth. In our enterprise we have many large ...
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2answers
88 views

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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3answers
22k 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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1answer
1k views

How to simulate Mac flooding attack in Cisco Packet Tracer?

I'm trying to see effectiveness of port security on Cisco switches using simulations in Packet Tracer.but first I need to run some Mac flooding address attacks on switches in Packet Tracer. Can anyone ...
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1answer
5k views

List all MAC Addresses of Router [closed]

I have a modem which has an embedded router inside, I was led to believe by sources on the internet that each network terminal has its own MAC address. By typing the default gateway IP I managed to ...
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1answer
118 views

can a switch participate in STP without MAC?

I was wondering if my switch that doesn't have MAC addresses assigned to any of its customer ports can even pareticipate in spanning tree protocol negotiations?
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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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2answers
13k 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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2answers
2k views

Gateway changing source MAC address in packet headers

My question might be broad but I was watching a Youtube video and thus I want to ask the following: Is it true that a gateway may change the source MAC address of some packets passing through it to ...
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1answer
63 views

Standard Gateway (Passive Network Partner)

Following scenario +-----------+ +-----------+ | Network A |--- Router ---| Network B | +-----------+ +-----------+ Question If a client in 'Network A' wants to connect to ...
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1answer
81 views

What info can be retrieved about a host from its IP address?

We gave every user a static local IP address, bound them with their MAC addresses, and provided them access to different resources. But, a user has spoofed their MAC address to connect using another ...
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1answer
1k views

Spoof MAC address of VLAN interface on IOS

Is there a way to change the MAC address of VLAN interfaces (switched virtual interfaces) on IOS? I would like to configure the MAC address of a Catalyst switch. Because all VLAN interfaces derive ...
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2answers
799 views

Computer mac address appearing on more than one switch

I have three HP Procruve switches and have been trying to find out which switchport my computer is connected to. I issued the following command on each switch: show mac-address my_mac_address And ...
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1answer
4k views

What happens with MAC table in switch when I disconnect some device?

I have found some information about switch MAC table here: How does a switch learn a switch table? . There is explained how switch learns MAC addresses but what happens when I manipulate cables? What ...
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1answer
170 views

How to best mitigate a switch mac-address limitation

If I have 15 switches on the same VLAN and each switch has an upper limit on mac-addresses of 16k, and one of them is reaching that upper limit of 16k, what would be the best approach to mitigate this ...
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2answers
4k views

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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2answers
429 views

How does a switchport learn a MAC address

I have a very basic question. How does a switch port learn a MAC address? In this scenario say a host is not trying to communicate with any one. It is just plugged in the switch port. Does the host ...
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1answer
2k views

Wireshark to capture router MAC's

Is there any way I can capture the router IP or MAC addresses along the path of a ping packet using Wireshark tool?
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1answer
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how are bridges handled in ARP?

assume want to send a packet from H1 to H3 and we have a network like this: **H1** A:a | | N **B1** E --- E:e **R1** F:f--- C:c**H3** S | | B:b **H2** How will ARP table look for these nodes in the ...
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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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1answer
2k views

Obtaining MAC address of an external IP

Is there any way to resolve an external IP address to a MAC address without access to the specific LAN? In other words, is it possible to obtain a MAC address for any given public IP? To my ...
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2answers
385 views

Is an Ethernet Packet sent to all the hosts on a network?

Is an Ethernet Packet sent to all the hosts on a network, and then all of them discard the packet except the right host to which the packet was sent to? This page here says: Local networks like an ...
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6k views

How do routers traverse packets to their destination?

Sorry in advance for such a noob set of questions. I understand that when set with the task of sending a packet to its destination, a computer first checks that the IP address of the destination is ...

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