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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Filter mobile devices MAC address

I am monitoring my network and I would like to know how many mobile devices are there. I am already filtering probe requests and matching MAC adresses with OUI identifier. However I have few doubts ...
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ARP request complexity squared?

Is it valid to say that the complexity of ARP requests in a broadcast domain increases squared to the number of participants, as in the worst case every participant wants to address every other ...
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3answers
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Using SNMP retrieve MAC addresses of directly connected machines to a switch

I want to get MAC address of machines directly connected to a switch using SNMP. I am querying dot1qTpFdbPort for this. But this returns all the MAC addresses learned by switch which includes machines ...
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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
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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 ...
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2answers
175 views

does MAC filtering provide security against MAC spoofing in wired networks?

i have googled about mac address spoofing.All I know is that MAC filtering is not much of a protection in wireless network.And in wired network it only works for routers that support MAC Filtering.Is ...
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1answer
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What happens if two hosts with the same MAC address are in the same broadcast domain?

I am aware that situation, where duplicate MAC addresses appear in the same broadcast domain, should never happen. However, if such situation happens, then how will the network work? I think one ...
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Did the LSB-first method of transmitting the canonical MAC address in Standard Ethernet have any specific advantages?

When MAC addresses are sent out they are sent such that the Group Address Indicator is the first bit of the Ethernet frame but when stored in memory this forms the LSB of the leftmost byte of the MAC ...
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138 views

Failing to obtain MAC

With the purpose of registering many users on a big network (~600 users), each user's IP and MAC are needed. Currently, I am using arp command to retrieve the MAC, but for some users, I recieve an "...
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Why each and every single port on Layer 2 switches need to have it's own MAC address?

A switch doesn't alter the frame, and source/destination mac addresses remain how sending host specified them,so let me say it again Layer 2 Switching never changes the frames means no changes in MAC ...
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Layer-2, static forwarding on a Juniper SRX?

I'm really new to Juniper, so I apologize if this is n00b question. I do, however, appreciate your guidance! Here is what I want to do: all traffic on ge0.0.0 and ge0.0.1 is to be redirected to fe0.0....
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IP Address and Layer 2

As per my Knowledge MAC address is required to communicate two machines...and on layer 2 (Switch) can't understand IP (if i am right)....suppose we have 2 systems (Sys1 and Sys2) with 2 different IP ...
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Cisco IOS: How to view MAC addresses on an Ethernet pseudowire

With two Cisco ME3600 (or similar MPLS & VPLS capable devices) running recent code [15.3(3)S], is it possible to show the MAC addresses passing over a standard MPLS encapsulated xconnect? In the ...
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3answers
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List of directly connected network devices by mac/ip?

I need a list of all devices that are directly connected to the cisco device I'm connected to through serial. I tried the arp table, but it contains more entries than I want since it spans multiple ...
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Won't GLBP confuse a switch's mac address-table?

Say for example two routers (R1 and R2) are connected to the same switch (SW1) and both routers have Gateway Load Balancing Protocol (GLBP) correctly configured as the First-Hop Redundancy Protocol (...
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2answers
204 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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When are MAC addresses used instead of IP addresses in the OSI model?

Okay, so I'm studying for the Network+ exam, and I've gone over the OSI model about a million times, and I understand most of it fairly well, and my studies are coming along fine. However, there is ...
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How can there be more than one MAC address on single switch port?

I am learning for the ICND1 exam through CBTNuggets video courses. In one of their videos they used a command, switchport port-security maximum This is what the cisco help says about it, To set the ...
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How are IP addresses mapped to MAC addresses?

I've been reading about the differences between MAC and IP addresses, and why we need both of them. To summarize, MAC addresses are physical unchangeable unique IDs for every single device while IP ...
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4answers
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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 ...
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4answers
618 views

Aren't MAC and IP doing the same job?

The question "What is MAC for?", "What is IP for?", and even "What is the difference between MAC and IP?" have been asked many times, even on these forums. Yet, there is STILL no clear explanation, ...
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6answers
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Finding Non-Cisco End Device IP Addresses Connected to Cisco Switch

I have Cisco catalyst switch, with many VLANs and address ranges. How do I find IP addresses connected to the switch that are not Cisco devices?
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List over assigned global Ethernet MAC multicast address

Where are global Ethernet multicast MAC addresses assigned? Is this by Organizationally Unique Identifier (OUI), and if so, is there a homepage that shows all the assigned global Ethernet MAC ...
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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 ...
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1answer
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Why ARP Cache clear when HSRP is already running

I have a scenario to discuss. There are three nodes that I am talking about. lets give those sites the name A, B and C. Site A and C has vendors routers installed. Vendor has no reachability for ...
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SVI as a DHCP client

Can a Cisco switch be configured to have a management interface (or SVI, or VLAN interface) become a DHCP client, therefore obtaining its own IP address on the respective network? This is out of ...
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Using SNMP to Find a Switch Port Number from a MAC Address [duplicate]

I am following this guide http://www.cisco.com/c/en/us/support/docs/ip/simple-network-management-protocol-snmp/44800-mactoport44800.html but it is not working for me. I have set this up on one network ...
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1answer
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What is the difference between ipNetToMediaPhysAddress and dot1qTpFdbPort?

I see the object description of ipNetToMediaPhysAddress from ipNetToMediaTable as the "The media-dependent `physical' address". Putting it simple, does it mean it returns the MAC addresses of all the ...
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2answers
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Why is the target IP address always my default gateway?

I am currently researching ARP packets using Wireshark and have found that when I ping a new computer asking for the MAC address that corresponds with the known IP address, my target IP address in my ...
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Differences and functions of type codes 0800 and 0806

What are the primary differences and functions (or applications) of type codes 0800 and 0806? Through my own research, I found the 0800 was related to the 0800 to the IP/Layer 3 of the OSI model. ...
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3answers
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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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3answers
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Is there any way to differentiate MAC address of an Access Point from that of a client?

If I have got a list of MAC addresses, is there any possible way to differentiate MAC of an AP from that of a Client. I am asking whether there is any pattern of the characters in the MAC address by ...
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Is it possible to use single MAC address for multiple IPv4 addresses?

Topology: modem with router and Ethernet LAN bridge <---> server having one NIC. Server network interface: It is capable of handling more than one IPv4 address. All addresses are within the same ...
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1answer
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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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3answers
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Why don't switches rewrite mac-addresses?

Is there any particular reason why Ethernet switches don't change the MAC address of a packet? Is it for end host identification using the MAC address, or anything else?
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1answer
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VLAN assignment based on mac-address or RADIUS attribute

I'd like to know how to assign someone's client device to a different VLAN based on MAC address of that device.What kind of hardware/software would make this solution possible (if possible at all)? ...
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3answers
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What to use as ARP request Target Hardware Address?

When sending ARP request, what must be filled in the target hardware address (THA)? This technet blog post says it is to be filled with zeros (0.0.0.0) -although doesn't look like a MAC address!, and ...
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How ARP works in case of Virtual machine?

As far as my understading goes MAC address is used to recognize a computer node in a LAN where as internet communications happen over IPv4 address. When a request comes from the internet to the ...
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4answers
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Switch Lookup Table

I was just reading a book called HeadFirst Networking and I'm a bit confused about something. I am attaching an image from the book. The page says that the direction of the frames as maintained in the ...
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1answer
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Microsoft NLB - static MAC necessary?

We've implemented Microsoft NLB before, but it's not a common thing for our environment, consequently I've not looked at the config in a while. The topology is: EDGE == 3750X's (stack of 2) == N5K's ...
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9answers
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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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1answer
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HP Procurve 3500 with K.14 - strange MAC search issue

I have strange issue with HP ProCurve J8692A 3500yl-24G. If I display MACs on port I see it: 3500(config)# sh mac 10 | inc 5cf3fc-a53456 5cf3fc-a53456 But if I try to find where is this MAC then I ...
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1answer
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Position of source and destination IP in an IP packet [duplicate]

In an Ethernet frame header, the destination MAC (DMAC) is placed before the source MAC for obvious reasons (stations accept based on DMAC). But why is not the same thing maintained for destination IP ...
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Will duplicated MAC address give problems, if in different VLANs?

A small company has 2 Cisco Catalyst 3550, with 24 ports each, connecting their equipaments. After some trouble, we found that two NICs had the same MAC address. After the initial reaction of blaming ...
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2answers
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How to infer 2960S switch base ethernet MAC Address

Cisco switches seem to allocate unique MAC address for each interface they have, this includes ports and vlan interfaces. These unique MAC are derived from a "Base ethernet MAC Address", which can ...
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4answers
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How to find a list of devices connected to my network (IP's and MACs)

I am trying to get a list of the devices that are connected to my Cisco (Catalyst 2960) switch. Preferably through SNMP. Here is what I've already done: I was able to retrieve the ARP table from the ...
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3answers
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ipv6 addressing /127 vs eui-64

Best practice is to use a manual /127 address for point to point addressing described here RFC2373 for EUI-64 ERFC 2373 dictates the conversion process, which has two steps. The first is to convert ...
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114 views

Data Link Messaging Protocol

Is there a way to exchange messages between two hosts in the same VLAN referring only to the respective MAC addresses? I am thinking of a sort of equivalent to the Phone utility in a VMS network.
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Why does ipv6 specify 128 bit address, when there are only 48 bits in MAC addresses?

So, I'm reading for a networking exam, and I'm just wondering if I have missed something basic. Is there a need for more ip addresses than MAC addresses, and how would a node with one network adapter ...

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