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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votes
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
5k views

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
9k views

When it comes to Computer Networks, what is a logical address and physical address?

I understand the concept of logical address, and physical address when it comes to computer memory. That is, physical is the actual address and logical address is what the applications think the ...
3
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5answers
684 views

Is there a Layer 2 address advertising protocol?

I needed help in understanding if LLDP/CDP is the Layer 2 equivalent to RIP or say any Layer 3 route advertising protocol. If not,is there a protocol that advertises the MAC Address Tables among ...
3
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2answers
202 views

Client timeout for Cisco IOS Static DHCP Pool

I'm not a network admin, but I have an old Cisco Catalyst 3560 for my network. I've successfully set up a DHCP Pool: ip dhcp pool 192.168.0.0 network 192.168.0.0 255.255.255.0 default-router 192....
3
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3answers
6k views

Is it possible to perform a Layer 2 (MAC address) traceroute?

I understand the difference between layer2 & layer3 and MAC & IP. I understand address resolution protocol, etc. But is there any way to do a traceroute that will show Layer 2 information? For ...
3
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3answers
453 views

How to tell which one is the source IP and MAC address of the data being received?

I have to work with an FPGA module already running a code written by someone else. I have no access to the FPGA code. Now the setup is something like this:- FPGA is connected to the pc via ethernet ...
3
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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 ...
3
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1answer
2k views

Why bb:bb:bb:bb:bb:bb is non-unicast mac address?

For testing purposes decided to add static IP addresses to my router for some mac addresses. For simplifity I started with aa:aa:aa:aa:aa:aa and assigned ip 192.168.1.100. These combination has been ...
3
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1answer
216 views

Switch MAC learning problem

I'm doing some research on switching algorithms using a Level 1 GSW-2476 switch and I have a problem regarding MAC learning. As far as I know, a switch stores the source MAC address of each incoming ...
3
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1answer
624 views

ICMP packet with correct mac address but wrong ip address

I was wondering what would happen if you send an ICMP request with the correct mac address but the wrong ip on a local network. Would the request reach the computer with the correct mac address since ...
3
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1answer
18k views

When switchport port-security violation protect( or restrict) is configured , how many times can the security policy be breached?

The switchport port-security violation shutdown , shuts the port (err-disabled) when the policy is violated. But, for restrict and protect modes there isn't a mention of shutting a port down. So, can ...
3
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2answers
331 views

LANs with no router,just a switch(or hub)

Can a LAN be implemented just with a switch? If so,how is the communication completed?just by MAC addresses? When sending a frame from the source to the destination,and inbetween there is a switch,...
3
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2answers
74 views

Possibility of using Cisco "port security" in sensor networks?

Is it possible to use Cisco port security (to prevent a host changing its Mac address) in sensor networks? In a more general question, is Cisco port security platform independent? Meaning that it is ...
3
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1answer
2k views

Possibly an issue with MAC aging

I've got three switches, one core switch/router (Brocade 6450) and two access switches (HP 2530) which are connected to the core switch. I also have a number of devices connected to the access ...
3
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3answers
601 views

What more information can I get from filtering by MAC address rather than IP?

I want to do some very simple traffic analysis for a single device. I'm using tcpdump to collect this data. Is there an advantage to using a MAC address capture filter over a (static) IP address for ...
3
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1answer
4k views

How to send packets to MAC address instead of IP address

I am working on a project where I will send data from one country to another which will be, according to the data sent, processed for commanding devices connected to the computer. The problem is: I ...
3
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4answers
188 views

Question about ARP requests

When a device tries to associate an IP address with a MAC address for a given device, it sends ARP requests to all devices connected to the same network. If I understand correctly, the searching ...
3
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1answer
689 views

Port Security Or 802.1X Authentication On Non-Server Network

I have a closed network of 3 switches and 40 computers. 35 of those computers (Windows 7 x64 Professional) need to be plugged into any of the 24 ports on 2 of the switches at any time depending on the ...
3
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2answers
370 views

Why do we allow Mac-Address to be changed by software?

In CISCO routers, they provide a provision to change the MAC-Address. My question is MAC-Address is supposed to be a burned-in address i.e. a permanent address. If we allow the mac-address to be ...
3
votes
1answer
2k views

Practical difference between MAC-48 and EUI-48

As mentioned at Wikipedia, The distinction between EUI-48 and MAC-48 identifiers is purely nominal: MAC-48 is used for network hardware; EUI-48 is used to identify other devices and software. (...
3
votes
1answer
8k views

Get MAC address of all devices (IP cameras) connected to switch

I am a beginner when it comes to networking, and I have done as much research as I can to try and figure this out on my own, but the more I read the more I realize I don't know. I work for a ...
3
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2answers
198 views

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 ...
3
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2answers
2k views

Get MAC address of directly connected network neghbor

I have a PC (in the successive diagrams pc1) equipped with a network interface that can be directly connected to another PC or to a managed switch. I want to be able to get the MAC address of the ...
3
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1answer
41 views

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?
3
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1answer
113 views

Port security on a cisco switch - predefined source MAC address and maximum number of MAC addresses

With port security on a Cisco switch, if you configure 1 source MAC address, does that also set the maximum MAC addresses to only one?
3
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1answer
784 views

Cisco ARP cache rewrites?

I know that the Cisco's default ARP entry expiration is 240 minutes, however how does the ARP table mechanism work when a different MAC address is seen using the same IP? In other words, if I move ...
3
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2answers
82 views

Why don't switch MAC addresses conflict

Switches apparently have a base MAC and self-generate MAC value for each port from that base. If a company that makes both switches and processor boards builds a switch and assigns it MAC "N" and ...
3
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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 ...
3
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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-...
3
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2answers
6k views

What is the difference between MAC and İP broadcast addresses?

As far as I know, they are both used to send a packet to all hosts that are connected to a local arena network. Why would anyone need two addresses to send a broadcast package?
3
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2answers
2k views

How to update the ARP table of a router or switch? could it be possible through broadcasting?

I have mac table list of router, now I am trying to get a Ip address for each mac address in mac table list. So i tried to use ARP, unfortunately ARP is missing some of the mac addresses mapping which ...
3
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2answers
425 views

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 = ...
3
votes
1answer
475 views

Is a network interface supposed to have no more than one MAC address?

Is a network interface supposed to have no more than one MAC address? Since a network interface is free to have more than one IP addresses, is IP address a way of multiplexing MAC address, if a ...
3
votes
1answer
140 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 ...
3
votes
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 ...
3
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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 ...
3
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2answers
52k views

How to send an ARP request manually? [closed]

I recently sniffed with Tcpdump a packet "ARP, Request who-has 192.168.2.3 tell 192.168.2.2, length 28". I would like to reproduce this message, and to send an ARP request from my laptop to any IP I ...
3
votes
3answers
8k views

MAC Flapping on Cisco 2960G

We've been having an issue for the last few weeks on a relatively small network. The issue started when we swapped a specific Cisco 3750 for a 2960G (there were some other changes), exactly since then ...
3
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1answer
115 views

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-...
3
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1answer
101 views

Global Unicast in IPv6 Neighbor Discovery

I have a very small pcap file in which Neighbor Discovery is performed for Global Unicast Addresses. That is, IPv6 addresses of both neighbors as I can see in Wireshark start from 2001:. Both IPv6 ...
3
votes
1answer
97 views

MAC addresses of hosts that violate port-security

Do hosts that violate port-security show up in the mac-address table, or is this only in the logs? What would the log entry look like that has the violating address? We're on Cisco 2960X.
3
votes
2answers
202 views

Is a source Mac Address required for two directly connected computers?

I've read different sources of information, and the only answer I found is that the source mac is needed to fill the switch's table (the one that maps the address to the port). Is it right? What ...
3
votes
1answer
56 views

Is it a protocol of flooding to find the MAC address?

Is it a protocol of flooding to find the MAC address? As we know, if the switch can not find a MAC address, it will flooding to every switchport except the entry port to find the corresponding MAC ...
3
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1answer
3k views

Ping a mac address to get it to reply and update mac address-table

I need to find out what port a MAC address is connected to. Given a Cisco 3750, I can do a show mac address-table dynamic and see all the mac addresses that the switch has seen frames travelling to ...
3
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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. ...
3
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1answer
148 views

Why use one MAC per port design in L2 switch for STP function

While I'm testing the STP function in several different Switches, I found Some Switches use single MAC address for all LAN ports (e.g. Buffalo's BS-G2108M, Netgear's GS716Tv3), while some other ...
3
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0answers
1k views

Juniper EX Unicast Flooding [closed]

I have a few Juniper EX3300 switches in my core. I'm seeing something strange where packets destined for device with the MAC address 00:90:0b:30:2d:f2 are being flooded out all interfaces. However, an ...
2
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2answers
7k views

How physical addresses change hop to hop?

I've been reading Data Communication book by Forouzan it says that "The physical addresses will change from hop to hop, but the logical addresses usually remain the same." So, according to this ...
2
votes
2answers
205 views

What happens at the destination end if it is in a WAN?

When the Sender gets to know that the destination is in a other network ( by doing the AND operation with the subnetting adress of its network ) what are the procedures followed, so the packet does ...

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