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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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1answer
33 views

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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2answers
2k 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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1answer
49 views

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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1answer
25 views

Why we need Mac address to send Packets? [duplicate]

While sending a packet network layer attach the source and destination Ip addresses to it. But Data link layer need a destination Mac address in order to send the data through router or within a ...
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3answers
69 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
33 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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1answer
101 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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1answer
21 views

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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2answers
102 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
127 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
105 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
41 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
55 views

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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2answers
110 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
32 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
44 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 ...
2
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1answer
100 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 ...
3
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1answer
50 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-...
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1answer
67 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 ...
4
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1answer
480 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 ...
2
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1answer
32 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?
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3answers
134 views

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 ...
2
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1answer
614 views

MAC Address Filtering Fortinet v6.0

I am having trouble configuring mac filtering. I do not use DHCP but am trying to figure out a way to set a mac address on a port and create a rule to block that specific mac address. So when I try ...
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2answers
77 views

Obtaining packet switch-port information via a mirrored port?

When sampling a mirrored port of a switch, is there any means of determining the switch-port information of the packet? Since Ethernet packets do not contain this information, I assume the answer is ...
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1answer
44 views

Mac Address Flapping and switches

Is mac address flapping the reason why switches don't exchange switching information just like routers exchange routing information?
2
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2answers
71 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....
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1answer
65 views

What is the meaning/translation of a MAC address?

For an instance : 00:0a:95:9d:68:16 I wonder if 00, 0a, 68 or 16 etc, has some specific meaning or can be translated, like giving the vendor information, date of issuing etc?
2
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1answer
59 views

MAC Address not resolving when IPSec VPN in place

I've created an IPSec VPN connection between two Mikrotik routers. They are connecting via IKEv2. Inside our two networks, we have a printer spooler which needs the printer's MAC address to verify it'...
2
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1answer
61 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 ...
4
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1answer
361 views

Will the Sticky MAC access policy prevent unauthorized hubs from connecting to a network?

We have Meraki MS 250 switches. I have discovered some personal hubs attached to the network and want to ensure these devices wont work on the network to discourage the behavior. From what I can see,...
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2answers
69 views

How is Ethernet traffic sent between computers with multiple switches in-between? [duplicate]

I've wondered how Ethernet packets sent from Laptop-A to Laptop-B on the local network segment are delivered, when multiple switches are in-between. For hubs, that just replicates the packet on all ...
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1answer
28 views

How does a system know the local gateways MAC address for given IP address [duplicate]

Assuming you have the following network structure. Knowing the IP address of the WWW-Server, system A wants to send an IP packet. As I understand the destination MAC address has to be in the same ...
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1answer
63 views

Wireshark remote hosts

I configured a rip network. I connected two PCS to router 1, router 1 is connected to router 2 and PC 3 is connected to router 2. When I pinged PC 3 and looked at this in wireshark, in the source it ...
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0answers
71 views

Juniper EX4300 / MAC limiting SNMP trap

I have the following device and configuration: Model: ex4300-32f Junos: 17.3R3-S3.3 show configuration groups GLOBAL-SNMP { snmp { client-list MANAGERS { 10.8.9.0/28; } community TEST-COMMUNITY ...
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0answers
20 views

Information passed through an access point to a router

We have WiFi routers that control access through ACL's. We would like to use Access Points (AP) to increase the range of the WiFi routers. Does the AP pass the MAC address of the client to the ...
6
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2answers
191 views

How to display entire MAC address table on HP switches

I want to display the whole MAC address table without needing to press 'space' for the next page, so that if there are 50 entries in the table I'd be able to view them with a single command. I'm ...
7
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4answers
2k views

Does every host on the LAN share the same ARP table, or do hosts keep them individually?

I'm just learning about ARP. I'm a little bit confused. My confusion is better explained in a scenario. Host A is communicating with Host B. Host A knows Host B's IP address, but not it's MAC address....
3
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1answer
393 views

MAC Table vs ARP

I understand that for a switch to learn a MAC address, if host A wanted to send data to Host B the switch learns host A MAC and places it in the MAC table. If it doesn't know where the MAC (for Host B)...
4
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3answers
317 views

Switch and mac address table

I thought that a switch learnt the mac addresses by the computers sending out packets. However when I configured 2 switches, and 2 pc's, 1 pc connected to 1 switch, the other pc connected to the other ...
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3answers
120 views

Is an IP address assigned only to something with a Mac address?

From https://en.wikipedia.org/wiki/IP_address An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol ...
3
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1answer
88 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?
2
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2answers
145 views

How does a router know the destination mac?

so if I send a packet from a host to another from the same network we know the mac address of both the source and destination. However if the receiver is in a remote network the destination mac ...
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2answers
43 views

What is the bridging decision when getting ARP request?

Setup: Assume I have 3 VMs. VM1 VM2 and VM3. VM2 has two interfaces, say eth1 and eth3. eth1 is connected to VM1 physically and eth3 to VM3. I create a bridge on VM2 using brctl with eth1 and eth3. ...
3
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3answers
442 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 ...
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2answers
86 views

Why we need ARP when each device has its own IP address?

I don't really understand Address Resolution Protocol (ARP). Why we need ARP when each device has its own IP address?
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1answer
175 views

locally vs universally administered MAC address? [duplicate]

Difference between locally and universally administered MAC address? What is the purpose of locally administered MAC address?
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3answers
267 views

If ARP uses broadcast, can I find out MAC-Address AND IP with it?

I have a peripheral device, connected via Ethernet to my Ubuntu. I would like to find out its IP, and untofetunately no it is not cached in my ARP table. ARP broadcasts the messages to every ...
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1answer
311 views

Private IP vs MAC

What I know is that when we connect to another IP, our Public IP gets shared to the outside world, and when they address us they use our Public IP (gateway), and then the gateway directs the ...
3
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2answers
37 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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1answer
266 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 ...