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 linux neighbor cache entries (whole-world-is-link-local syndrome) (linux 3.0.0-16)

On absolutely standard ubuntu-server linux distro running only BIND cache, sometimes i see non-link-local ip addresses in the arp/nei table and there is no way to communicate with those entries After ...
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Linux: arp cache timeout for non existent hosts?

In Linux, is there a different arp cache timeout for non existent hosts? At my router, 192.168.0.1, i'm seeing aprox. 8 new entries every 10 seconds for an IP that has been down for a long time. ...
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Detecting network state with arping

I am developing system for detecting network actual state. One part is to get all IPs and their respective MAC addresses. Right now I am using arping in DAD (Duplicate Address Discovery) mode. I send ...
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Machine always responds to 192.168.1.2 IP address, which is not set on the machine

UPDATE BELOW: UPDATE 2 BELOW: FINAL Solution I have a brand new HP EliteBook notebook 8560p running Windows 7 64bit. I plug it into a small Dlink di-604 router, it is currently configured with DHCP ...
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Where is the arp_cleanup_interval variable in Solaris 11?

In Solaris 10 I can configure (and audit) the arp_cleanup_interval variable using the following command: $ ndd -get /dev/arp arp_cleanup_interval 300000 In Solaris 11 (Express and Release) the same ...
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Why does a PXE-booting VM aggressively seek Reverse ARP?

Reverse ARP is.. well, pretty much dead, as far as I'm aware? One of the great Internet success stories in killing off a protocol? It's been deprecated in favor of BOOTP (and later, DHCP) for almost ...
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How to setup a static multicast ARP entry with Cisco SG300?

We're running a Microsoft NLB cluster in multicast mode as a loadbalancer. Using our old Cisco IOS switches we propagate access to the cluster to our branches using a static ARP entry in the core ...
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How do I prevent excessive ARP requests sent from Windows Server 2003?

OK, I've scoured the 'net already for possible solutions and have found none. Maybe you guys can help me. I have a Windows Server 2003 setup, with a fixed IP on a routed LAN, standard /24 network. ...
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Linux storing arp cache entries using wrong interface

I'm trying to get two virtual machines (running CentOS) to talk to host (Ubuntu 10.04) using VDE and the outside network. So far I'm running into an ARP issue. On Host I have a physical eth0 and a ...
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Adding entries for incoming arp requests to ARP cache?

Given a host A und B within the same broadcast domain whose ARP caches are both empty, under what circumstances would B add an entry for A to its ARP cache when replying to an incoming ARP request ...
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960 views

Many ARP requests in TCP dump?

I have been experiencing very slow upload speeds on my cable network lately. I ran a tcpdump and found many ARP requests. I'm not sure what process they are coming from, but could this be related to ...
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Why is my Nexus 5548UP not adding ARP entries for the trunk to a 2960S?

I have a Nexus 5548UP trunked to a Catalyst 2960S. I have verified that spanning tree is working. I explicitly made the 2960S the root bridge for all VLANs as a temporary measure since it is trunked ...
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Windows Server 2003 DC sends Gratuitous ARP requests with wrong IP

Hello and excuse me for my English please. ;-) Two server seems to be involved with this problem. Our DC (domain controller, 2003) an the VMware VC-Server (2008 R2). After capture "some" network ...
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Should a Dell 5424 switch have an arp entry for every machine connected to it?

I've got a Dell 5424 with about 20 machines directly attached to it. I did a ping sweep of my network (and got answers from all 20), then went to the CLI of the switch and did show arp. To my ...
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ARP reply vanishes from br0 to tap0 using OpenVPN in bridging mode

i have setup a linux box (on an esxi5) which acts as an openvpn server. the server is configured to use bridging for the clients, which essentially works, with one exception. if the client pings some ...
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linux routing bug?

I have been struggling with this not easily reproducible issue since a while. I am using linux kernel v3.1.0, and sometimes routing to a few IP addresses does not work. What seems to happen is that ...
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Why need to send ARP to ask for MAC address when IP address is already unique? [closed]

In the usual networks, since every host has a unique IP address recognised among the stations in the network, why is a MAC address still necessary? Suppose a station A wants to send to Station B. ...
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arp requests are sent continuously and my linux machine disconnected to the world [closed]

I have the following problem and really need your help I'm implementing a small server to receive request from client on port 18999(just sample) using TCP socket. When I tested my server by using a ...
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Which NIC have the IP address?

If I have two NICs where I know the MAC addresses. Without logging into the server, how do I figure out which have the IP address 10.10.10.10? Can arp somehow be used for this?
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postgres fallback to standby server, switching ip address, clear ARP cache

I'm using a hot standby server for my postgres database. I've assigned a virtual ip address to the server. In case of a failure I'm switching the virtual ip from the master to the hot standby server. ...
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ARP requests, etc.

I'm trying to run arp spoofing on a network. I've been working on this for about a week, and all the information I find is dated year 2000-2001. My issue is, after testing a script that uses ...
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ARP discovery on multiple subnets

I have an unmanaged switch which serves traffic belonging to different subnets. Lets say these are the subnets: 192.168.0.0/24 192.168.1.0/24 192.168.2.0/24 And few more subnets which I am not aware ...
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Pinging an interface of same network on same host not working

I'm setting up a very basic IPS test, and wondering if an interface on a host pings an interface with a different IP address (of same network) on the same host, will it reply? Will it respond to ARP ...
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Multi-NIC Linux machine's NICs are responding to each other's ARPs regardless of arp_filter setting

I have an old Linux machine running a 2.4.37 kernel. In the machine are two NIC cards both on the same network with different IPs. For some testing, we want each IP's traffic routed through that NIC, ...
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Sporadic routing(?) issues

We are running several virtual machines using KVM with libvirtd with a routed network (the host systems routes an extra subnet for the virtual machines). Host and Guest OS is Gentoo (host on amd64, ...
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Solaris does not record MAC address in ARP table

I have noticed that a Solaris 9 server keeps sending ARP requests for an IP address that is owned by our DNS server. The DNS server answers with its MAC address but Solaris 9 does not record the ...
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How to test 10 gigabit Intel X520 on Ubuntu

I got Intel X520 and connected it to PCI-E x16. The card is recognized as 10 Gbit by ethtool: # ethtool eth5 Settings for eth5: Supported ports: [ FIBRE ] Supported link modes: ...
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Direct server return, ARP problem

I'm trying to implement Direct Server Return scheme for our web cluster and I think i got stuck with some ARP issues. For testing purposes I deployed 2 virtual servers (inside ESXi environment). Host ...
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arp table filling up

I have a CentOS 5 system which serves as an IPSec VPN connector between my network and a couple of remote networks. Lately it is running into this problem once or twice a day where its ARP cache gets ...
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how can I stop my sonicwall TZ-210 (SonicOS Enhanced 5.5.1.0-5o) from responding to arp queries on the wan subnet?

My sonicwall TZ-210 is answering arp queries on the wan subnet (which my isp doesn't like), basically mapping all the wan ips to its own mac address, causing network havoc since it is not set to route ...
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Is there a config file for ubuntu server like /etc /ethers to config the mac-ip bind?

i can't find /etc/ethers in ubuntu server:< i want save something like "sudo arp -s someipaddress macaddress" so i don't need to set it again after reboot
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Is there a way to disable outgoing ARP requests on the wan interface on a sonicwall TZ 210

My internet provider is having a lot of trouble with excessive ARP requests coming from a sonicwall TZ-210. I need to tell the sonicwall not to send so many or to send no ARP requests at all from the ...
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Hardware won't respond to each others ARP requests

I have two pieces of hardware (embedded devices) that I have setup to communicate via TCP over Ethernet in a client/server fashion. The topology of the network is as follows: ----- | S ||=|== Debug ...
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Is this how ARP works? [closed]

A wants to send a datagram to B. A knows B's IP address. However B's MAC address is not in A's ARP table. So A broadcasts an ARP query packet to all machines on the LAN. B recognizes it's IP, so it ...
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Windows 2008 ignores Gratuitous ARP requests

We recently saw an issue after a fail over of our router where our Windows 2008 Boxes didn't start talking to the primary router after fail-back. When we did some digging they still had the ARP ...
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How to find the process which causes the arp request?

When i run tcpdump in the gateway, i get a lot of arp requests originating from the gateway itself. I wonder know why this happens. How can i find the process that causes these arp requests? $ ...
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ARP request are sent even though windows has an entry in cache (ARP Table)

we have a product which runs on windows XP embedded SP1. We add a fake(does not exists) MAC address for a fake IP in ARP table. When there is a communication happening Windows sends packets to the ...
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What would cause a Windows 2008 server to switch destination MACs in the middle of a TCP session?

My Windows 2008 server started a TCP session talking to one destination mac address, but in the middle of the TCP session started sending packets to another destination mac address and then eventually ...
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Effects of having a rapid ARP flush

So the scenario is we have a web server at our colocation. In front of that web server are two SonicWalls and two L2 non-stacking managed switches. We're trying to find an efficient way to set up ...
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Linux is not sending arp request

We have a local network that is connected to internet through linux gateway. There are about 50 workstations in LAN. We recently started observing a problem that gateway sporadically stops responding ...
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Need confirmation on layer 2 security question

I need confirmation on a question regarding layer 2 security. I've been doing research and I just need to know that I understand it correctly. Basically, if you have a LAN with a few machines ...
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ARP replies contain wrong MAC address

I've got a robot running linux with wired and wireless adapters. When I boot up, it connects to the wireless fine. When I assign an IP to the wired (either statically or with DHCP), it looks like it ...
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Is it possible to disable ARP in Windows 7

I have a unique requirement where I need to disable ARP on a Windows 7 box. In previous Windows versions you could modify the ArpRetryCount in the registry (and set it to 0), but this does not work in ...
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Windows 2008 R2 Servers Sending Arp Requests for IPs outside Subnet

By running a packet capture on my my routers I see some of my servers sending ARP requests for IPs that exist outside of its network. For example if my network is: Network: 8.8.8.0/24 Gateway: ...
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Clear arp cache

How to clear arp cache ? How to refresh arp table ?
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No answer on arp requests?

I have a problem where my Layer 3 Dell PowerConnect 6248 Switch (main switch) will sometimes (that means sometimes it works, sometimes it won't) not get an arp response from a device behind Dell ...
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Same native and tagged vlan possible on Redhat?

I'm looking at implementing a systems using a number of tagged and a native vlan connected to a server over a a/p bonded interface. The untagged vlan is for physical machine access, the tagged vlans ...
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Ettercap - packet injection / alteration

So I have a proxy setup using squid on port 3128. I also have ettercap setup. My main goal is to change data as it flows through my proxy. Basically, you open up www.something.com using my ...
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Why my laptop sends ARP request to itself?

I have just started to learn about protocols. While studying the packets in wireshark, I came across a ARP request sent by my machine to my own IP. Here is the details of the packet : No. Time ...
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Computers on one subnet can't connect to the internet

I have an issue with my student computers - they can't connect to the internet. Here's the weird part: I open a command prompt and ping our gateway server, and suddenly everything is fine (at least ...