17 votes
Accepted

Why do some mac-addresses repeat so often?

This example in particular (58-2C-80-13-92-63) is a USB Ethernet chip made by Huawei. Looks like they're being lazy and reusing the MAC. Examples from Google: [50413.229125] cdc_ether 2-1:1.0: eth1: ...
MikeyB's user avatar
  • 39.6k
9 votes

how to generate a random MAC address from the Linux command line

These variants work as well. longer: openssl rand -hex 6 | sed 's/\(..\)\(..\)\(..\)\(..\)\(..\)\(..\)/\1:\2:\3:\4:\5:\6/' or shorter: openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/:$//' The load ...
Jaroslav Kucera's user avatar
8 votes
Accepted

Why does two different interfaces on the same machine result in two different MAC addresses?

You are right that one device has one MAC address. Your wireless card is considered one device. Your Ethernet card is considered one device. Every Network Interface Card (NIC) is one device and has ...
user5870571's user avatar
  • 3,144
6 votes

Physical interface MAC rather than macvlan MAC is sent as ARP response

Basically, nothing is wrong here. This is how Linux kernel works in regard to ARP resolution - by default it will reply to ARP requests for any of its local addresses regardless of interface they are ...
Peter Zhabin's user avatar
  • 2,871
5 votes
Accepted

Does a private MAC Address range exist?

You want to set the universal/local bit in the MAC address to 1. This is the second-least significant bit of the first byte of the address. All MAC addresses physically assigned to real hardware will ...
Michael Hampton's user avatar
4 votes

Monitor for duplicate MAC addresses?

Do you have managed switches? I suspect my approach might be to periodically pull the mac tables (cam table) from all your switches/network devices and then store them in some kind of database or ...
Zoredache's user avatar
  • 132k
4 votes
Accepted

Debian: Where does a bridge interface store its MAC address and how can I change it?

The overall behavior is caused by systemd, even if systemd isn't configured to manage the system's network. A bridge interface on Linux has two "modes" with its MAC address: the implicit ...
A.B's user avatar
  • 12.7k
3 votes

Why does two different interfaces on the same machine result in two different MAC addresses?

Each network interface, whether wired or wireless, is a unique device and as such will have a unique MAC address. https://en.wikipedia.org/wiki/MAC_address
joeqwerty's user avatar
  • 111k
3 votes

how to generate a random MAC address from the Linux command line

Here are five other options, all of which use random bits for the least significant bit of the most significant byte that indicates if the address is unicast or multicast and for the second-least ...
nisetama's user avatar
  • 131
3 votes
Accepted

Ubuntu 16.04, Keepalived VMAC

I have solved my own issue...for the curious, here's the blow-by-blow. First, make sure to carefully check your sysctls, as Ubuntu has some enabled by default you would not expect to be enabled by ...
Jason Keller's user avatar
3 votes
Accepted

Physical interface MAC rather than macvlan MAC is sent as ARP response

For this to work for me I had to add one step to the accepted answer and set the following additional variable: net.ipv4.conf.all.rp_filter=2 I did not need to set arp_ignore to 2, 1 seemed to work. ...
Sean's user avatar
  • 146
3 votes

Linux easy way to extract MAC address per device

You can easily get the MAC address of an interface using: cat /sys/class/net/eth0/address
Khaled's user avatar
  • 36.9k
3 votes

how to answer a who has arp request

You can configure a single machine with a static IP address matching the ARP request and a proper netmask. The netmask has to be short enough to cover both the requested IP and the IP of the machine ...
kasperd's user avatar
  • 30.7k
3 votes

iptables is occasionally logging MAC addresses. Why?

The MAC information is only logged for devices on your local network. It is actually a hex dump of the ethernet MAC header and consists of the source MAC address (00:26:a9:7b:c9:30), destination MAC ...
Nedry's user avatar
  • 98
3 votes

Possibility of detecting MAC address spoofing in a decentralized network?

it is practicable to detect MAC address changes in a network of course, and there are tools available, e.g.: https://github.com/craig/ge.mine.nu/tree/master/arpcheck Best practice would be to only ...
Craig's user avatar
  • 570
3 votes
Accepted

How to run several ESXi VMs that must have the same MAC address?

You don't want VMs with the same MAC on a single vSwitch port group, that's how they work. If I had to do this I'd end up creating 7 port groups, one for each VM, then if you have to route between ...
Chopper3's user avatar
  • 102k
3 votes

Centos 7.6 MAC addresses change for a network interfaces

For whatever reason, your system has disabled consistent network device naming. This means that instead of using modern device names for interfaces, which remain the same for each NIC, on every boot ...
Michael Hampton's user avatar
3 votes

can ping but not arping via OpenVPN

OpenVPN tun point to point links do not have MAC addresses and thus you can't use arping with them. Or anything else that uses ARP or requires MAC addresses.
Michael Hampton's user avatar
2 votes

Duplicate MAC address in VMware deploying from template

I've seen similar issues after upgrading vCenter with old customization profiles, after some version upgrades the profiles become flaky. The usual fix is to just recreate the customization profile ...
Stuggi's user avatar
  • 3,576
2 votes

Resolve MAC address to vendor BASH

A MAC address starts with a 24-bit number, the first three octets, that uniquely identifies a vendor or manufacturer called the OUI (Organizationally Unique Identifier). OUI's are assigned by the ...
HBruijn's user avatar
  • 80.3k
2 votes
Accepted

How can I create a top priority firewall rule for a trusted mac address?

MAC addresses are only relevant on a local subnet - your VPS can't see your remote devices MAC address. In short, you can't achieve what you're trying tobdo.
Dan's user avatar
  • 15.5k
2 votes
Accepted

Port forwarding by MAC address problems

There is no such thing as "Layer 2 Port forwarding". The MAC Layer is just the access layer, there are no ports to connect or forward. I think your router is learning just one IP from it's connected ...
bjoster's user avatar
  • 4,907
2 votes
Accepted

How can I set the external interface for my bridge to be the same as my primary interface using networkd?

According to the manpage of systemd.netdev you can add a MAC address in the [NetDev] section. [NetDev] Name=bridge0 Kind=bridge MACAddress= Just insert the MAC address of eth0 there.
Thomas's user avatar
  • 4,305
2 votes
Accepted

VXLAN format details

VXLAN is a layer 2 framework so when one VTEP wants to send data to another VTEP, it will create a layer 2 VXLAN frame (basically an Ethernet frame). This frame then needs to be delivered to the IP ...
USD Matt's user avatar
  • 5,391
2 votes

ARP table not updated until response is sent

The arp command when run as the root user has the facility to delete and add entries into the mapping table locally. However, I'd advise against this unless you have some type of special need. An ...
mdpc's user avatar
  • 11.9k
2 votes
Accepted

Can I use source MAC of Ethernet packet for UDP reply instead of ARP lookup?

What comes to mind for me is if you have asymmetric routing between your hosts A and B (I use B for the embedded device in the question). Ie, a network setup such that the route from A to B is not the ...
Håkan Lindqvist's user avatar
2 votes
Accepted

Why do some unknown hosts show up with nmap option-sL , and not with -sn [and do I need to worry about them]?

Nmap's -sL option is the "List scan", which is not actually a network scan. It's purpose is simply to list the targets that were given as input, regardless of whether they exist or respond to any ...
bonsaiviking's user avatar
  • 4,450
2 votes
Accepted

Is it possible to check the MAC address of TCP-connected host (on same LAN)?

Socket APIs at layer 3 and 4 don't see the layer 2 MAC address. That requires investigation of the neighbor discovery cache. (And that your network stack involves MAC addresses at all. Although Linux ...
John Mahowald's user avatar
2 votes

if all of the world used IPV6, there is no need to have mac address anymore?

IEEE 802 networks (like Ethernet and Wifi) would still require MAC addresses to function.
Bert's user avatar
  • 3,003
2 votes
Accepted

How to give permissions to local computers using computers' MAC addresses in Windows Server 2016 for file sharing

I'm not sure why you would want to use the MAC address to designate share permissions but the short answer is no. MAC addresses can be spoofed so that wouldn't be a very secure setup. Anybody would be ...
Justa Guy's user avatar
  • 187

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