Address Resolution Protocol is a layer 2 networking protocol used for resolving layer 3 addresses (such as IP addresses) into layer 2 addresses (such as Ethernet MACs). It is used by network devices when communicating with devices on the same layer 2 network.

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Strange network issue when moving EC2 elastic IP

Recently we had an issue with a Windows 2012 EC2 server, which meant that we had to move across to another instance. We duplicated the instance, ran some tests and moved over the elastic IP. Should ...
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arp problems with transparent bridge on linux

I've been trying to secure my virtual machines on my esx server by putting them behind a transparent bridge with 2 interfaces, one in front, one at the back. My intention is to put all the firewall ...
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Must an ARP broadcast query packet contain the target node's MAC address [closed]

So far as I know, Address Resolution Protocol (ARP), translates the IP address of a computer on a local network to an equivalent layer 2 address (MAC address), such as sending a packet from machine A ...
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80 views

Determine the hostnames of IP conflict

I have a network with several hundred machines on it. I have a machine that gives intermittent connectivity issues, reported via vSphere web client. This troublesome machine has the hostname ...
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3answers
60 views

Linux (Ubuntu 12.04) sending ARP requests over single interface

I have a system with custom hardware hooked up to 2 different ethernet ports on the same system. The interfaces are configured on the same subnet because the hardware (FPGA-based) has a hardcoded IP ...
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58 views

localhost answering wrong ip

No idea how/why, but here's what I'm seeing. Consider 3 CentOS 5.10 boxes: Host A [10.1.2.7] Host B [10.1.2.8] Host C [10.1.2.9] All of a sudden we're getting strange behavior from Host X, ...
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3answers
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Prevent Linux server host from using ARP

If I know all client will connect to the sever with the same MAC address and to the same interface, is it possible to prevent from server host to send ARP request for each new client IP it gets a ...
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66 views

VMXNET3 nic loses the ability to update ARP table after N hours

I have a fedora 18 VM that stops updating the arp table on eth1 after running for a number of hours to days. There are other VMs on the same hypervisor that can access all of the same networks without ...
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1answer
102 views

“Destination Host Unreachable” and ARP returns no addresses over LAN

I am currently trying to setup LAN over two machines with a network mask of 255.255.255.0 however I am receiving the following message when trying to communicate between them both; [root@alpha ~]# ...
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1answer
68 views

network level of veth doesn't respond to arp

I decided to play with veth : create a veth pair and send a ping from one end to another. $ ip link add type veth $ ip addr add 192.168.99.1 dev veth4 $ ip addr add 192.168.99.2 dev veth5 $ ip link ...
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86 views

Switch behavior on unicast packets when the destination is unknown

Please let me start by saying I am no network expert, I am a programmer who does a fair amount of L3/4 programming. My question is that when a switch receives a packet with a destination MAC that is ...
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4answers
85 views

Find out IP of connected interface?

Suppose I connect two machines directly together with an ethernet cable. I know nothing about machine2's configuration - I only have access to machine1. What can I do on machine1 to determine ...
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2answers
222 views

ARP responds with single MAC address on Linux server with multiple interfaces on the same network

Linux server has 2 active network interfaces: IF:eth1 IP:192.168.1.1/24 MAC:11:11:11:11:11:11 (1GbE) IF:eth2 IP:192.168.1.2/24 MAC:22:22:22:22:22:22 (10GbE) The idea is that the ...
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1answer
34 views

Can Windows Populate Network List in an MPLS?

With an MPLS of one host and one remote, when I go to Windows Explorer and bring up "Network", is the list supposed to be populated with the devices on both subnets? If not, can it be made to do so? ...
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1answer
303 views

brctl bridge forwarding packets to promiscuous interfaces

I have two promiscuous sniffing interfaces on my linux box: eth0 is connected to an external vlan bridge eth1 is connected to an internal vlan bridge with eth0 I can sniff all traffic on my ...
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44 views

Duplicate entries in switch ARP table

A server is showing twice or more on my L2 switch ARP table Same IP address, mac address, and ethernet port. What could be causing this? Thanks
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1answer
105 views

nmap and arp-scan inconsistent IP-MAC results

I seem to get variable and inconsistent results for the IP/MAC addresses from a particular machine, using nmap or arp-scan. The machine has 3 interfaces, and this is what it shows: $ uname -a Linux ...
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1answer
55 views

what would happen when macchanger to gateway mac address? [closed]

I thought arpspoof GATEWAY_IP -t VICTIM_IP can be prevented by add a static arp entry on victim side, i.e. arp -s GATEWAY_IP GATEWAY_MAC I read ...
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91 views

Configuring VRRP with keepalived on two machines - interaction with proxy arp

Let's assume we have the following topology for our network: Host1------- Router1-------Router2----------Router3-------Host2 and we want to configure vrrp on the two hosts with keepalived so that ...
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2answers
52 views

Is Windows Server 2008 R2 arp cache per user or per machine?

When running arp -a in a Windows Server 2008 R2 prompt, will the returned entries cover connections from all users logged on to the machine or only the current?
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1answer
68 views

How to convert proxy ARP setup to IPv6?

My company has a router/firewall deployed with the "common" Proxy ARP setup: it sits between some servers and the ISP gateway, and intercepts all the packets with proxy arp, so that it can apply both ...
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80 views

Ubuntu 12.04 reply ARP request delay 10+ seconds

I'm running Ubuntu 12.04 in VirtualBox, my server program is running in it, its IP is 192.168.1.105. My client is running at 192.168.1.107. But the client alway took 10+ seconds to send a package to ...
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1answer
190 views

Networking ARP table in windows cmd

I am reading the book practical packet analysis and I have just learned the fundamentals of the ARP protocol. They also added something about the arp -a cmd command. I'm curious about some of the ...
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41 views

Router Advertisement loopback

I have a machine acting as a router. To send out router advertisements it is running radvd. IPv6 enabled. When an interface is enabled (e.g. a link-local address is set) radvd will sent to all nodes ...
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2answers
190 views

Windows Domain controller ARPing for 169.254.0.0/16 addresses

I've been doing some sniffing on my company's network to try to clean up some of traffic and have noticed that one of our Server 2008 Domain Controllers is sending out ARP's every second or two to ...
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279 views

Physical switch not learning MAC address of virtual machines

I have a virtual environment running vSphere 5.1. I have two ESXis with a vDS between them. There is, for the purposes of the discussion, just one portgroup on that vDS configured to use a VLAN. The ...
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187 views

arpd does not send ARP requests

Sometimes a botnet (or whatever) tries to port scan pretty much all IPs in the internal network (two /21 subnets) in one second. As a result the router sends out a lot of ARP requests and some slower ...
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1answer
73 views

iptables arp compare and execute

EXAMPLE: iptables :internet - [0:0] -A internet -m mac --mac-source 48:5D:60:FC:29:B0 -j RETURN COMMIT [root@localhost:~ ] $ arp Address HWtype HWaddress Flags Mask ...
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1answer
47 views

Understanding ARP traces during OS load

Consider the following ARP packets captured while a unix machine was booting. From the packets I understand that this machine whose MAC address is 00:22:22:22:22:22 is requesting information about ...
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113 views

Keepalived failover not working for Static NAT target behind Cisco ASA

I've got a Cisco ASA[0] with a pair of Linux boxes in the DMZ running Keepalived and HAproxy acting as a load-balancing failover pair for another pair of Windows servers, also in the DMZ. I'm ...
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1answer
64 views

Move IP from one server to another without disruption

I have an internal DNS server running on a VM. I've rebuilt the server from scratch in a new VM, and I want to cut over from the old to the new at some point. In order to do this, I'll need to take ...
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81 views

I am not able to connect to my server from my leased line internet connection

I am having some troubles connecting to my Fedora server from my static IP ISP connection. Usually I can ping that server with no problems. But other times it just gives me timeout responses. When ...
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1answer
511 views

ARP response is not present on the other port of linux bridge based on ubuntu 13.10

I recently build linux based bridge for packet monitoring purpose, but there is BIG problem. the environment is, overall env. target of monitoring is VMs on vSphere. two vSwitches are configured ...
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2answers
488 views

Multiple NIC arp issue

I'm troubleshooting an issue on Centos 6.4. I have a few systems setting up for greenplum. Each one has two "interconnect" interfaces connecting to an isolated subnet. It is like a cluster ...
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59 views

Redhat 6.1 LVS (DR) over private subnet

I am trying to run LVS on RHEL 6.1, but with traffic from the routers to the real servers over a private subnet. with direct routing (behold this drawing: http://i.stack.imgur.com/aJ22w.png) ...
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1answer
522 views

Linux arp cache timeout values

I'm trying to configure sane values for the Linux kernel arp cache timeout, but I can't find a detailed explanation as to how they work anywhere. Even the kernel.org documentation doesn't give a good ...
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5answers
4k views

ARP broadcast flooding network and high cpu usage

Hoping someone here might have some insight to the issue we are facing. Currently we have Cisco TAC looking at the case but they are struggling to find the root cause. Although the title mentions ARP ...
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41 views

embedded linux is arping gateway periodically

I have embedded linux box, It sends arp to gateway periodically. If there is no connection with gateway, it sends more (3 arp request) permanently , and there is no ip packet going out from my linux ...
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108 views

Solaris 10 invalid ARP requests from 0.0.0.0? Link up/down every hour or 2

The guys at the data center where I'm hosting a server running Solaris 10 are telling me that my server is making a lot of invalid arp requests. This is an example of a portion of what was sent to me ...
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117 views

How to capture arp table when using network bridging?

I have a computer with 2 NICS that are bridged and I need a means of distinguishing between machines connected to eth0 from machines connected to eth1. I was hoping to use something like the "arp -a" ...
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2answers
366 views

Can a computer route IP trafic between two LAN if it is not configured as gateway? [closed]

Having two LAN, each one have its own gateway, DHCP and internet connexion LAN 1 - IPs: 192.168.0.0-255, Mask: 255.255.254.0, Gateway: 192.168.0.1 LAN 2 - IPs: 192.168.1.1-255, Mask: 255.255.254.0, ...
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1answer
56 views

Host not showing in ARP even after broadcast

serverfault community. What I would like: to determine the current IP of a host (a networked camera to be specific) What I have: its MAC, its previously documented hostname and IP What I have ...
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1answer
113 views

How to discover devices other subnet [closed]

Printers like some thermal I have tried Bixolon and samsung laser printer ,even mikrotik router have a tool where they discover the device via its mac address.No matter what the ip is. And they ...
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57 views

ARP Tables on Windows vs Linux

I noticed on Windows Server 2008, Windows Server 2008 R2, and Windows 7 that IP multicast groups joined by a computer are recorded in the ARP table as static addresses automatically. However, the same ...
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1answer
165 views

Same network on different interface

We work with devices that are flashed (factory) using TFTP on a usb network connection. The server has a fixed 192.168.2.100 address and the device a fixed 192.168.2.101 address. When it starts, it ...
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2answers
207 views

Excessive ARP request with no reply

I had been monitoring our LAN setting due to slow bandwidth. In the wireshark, I am seeing an ARP request that is never resolve to a MAC address from the same IP address. I did a NMAP scan, the ...
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2answers
309 views

Why do all computers on my network have the same MAC address?

I'm on a LAN provided by an ISP. My computer has its IP address, Subnet Mask, Default Gateway, DNS Servers(using DHCP). I just wanted to see the MAC addresses of all the computers on my LAN. After ...
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1answer
566 views

How to resolve an IP address to hostname

This is my first time trying to work with an ARP so I'm slightly lost as to what I'm missing. I'm probably going down the wrong track, so lemme know if I'm completely and utterly off. What I'm trying ...
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1answer
159 views

Cannot ping gateway

I replaced my aging fileserver with a new server running ESXi 5.1 and migrated my fileserver in a virtual machine running on it. Now I have the following problem with this VM: I'm getting the ...
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2answers
584 views

Multiple NICs with IPs from same network at Linux host respond to a single MAC

CentOS host is armed with multiple NICs. All NICs are bound to the same subnetwork (let it be 10.0.0.0/24). Their IP configuration is provided with DHCP server (as reservations). While trying to get ...