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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Is there a way to trace what's sending gratuitous arps?

We have a box that's just started acting up and we're not really sure why. It has IP address (dummy examples) 199.199.199.1 on eth0, 127.0.0.2 on eth1, and 199.199.199.2 on eth1:0. Recently, for some ...
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1k views

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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1answer
449 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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404 views

Windows Server 2008 ARP Cache Poisioning

Recently ran into a very strange problem. Several applications were having issues communication through our F5 Load-Balancer. When we looked into it we found that the router had an incorrect ARP and ...
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1answer
415 views

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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1answer
62 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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1answer
302 views

openvpn connects but does not work until server pings client

I'm trying to configure a connection using openvpn from a windows 7 client machine to a linux host. I'm using openvpn in the traditional routed mode using tap devices, and the configuration I'm using ...
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1answer
204 views

Proxy arp and 1:1 NAT

I have a Linux router with 2 NICs doing masquerade from network 192.168.0.0/24 to an ADSL router. users <----> NIC A [router] NIC B <----> INTERNET Now I'm experimenting with proxy arp ...
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1answer
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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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1answer
421 views

Solaris Slow ARP Failure Unreachable Host

We have been experiencing slow timeouts for unreachable hosts is extremely slow. Recent testing in our lab shows it may be a delay reporting negative ARP lookups. Dumping traffic during attempts to ...
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1answer
215 views

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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534 views

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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1answer
384 views

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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114 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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520 views

Dynamic ARP Entries turning into Static ARP entries

I recently acquired a client that has a strange ARP caching issue on one of thier servers. I have a server that will eventually start turning it's dynamic ARP entries into static ARP entries. This ...
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196 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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115 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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141 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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60 views

ipwatchd detects non-existing conflict?

Ipwatchd is telling me about a conflict that I just do not understand. As far as I can tell, there is no conflict. Am I reading the message wrong? It's a Xen machine with the following network ...
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74 views

Can ARP with IP aliases on Windows be made to behave like on Unix?

On FreeBSD, when I have one interface with two IPs: ifconfig nic0 192.168.0.1 netmask 255.255.255.0 ifconfig nic0 alias 192.168.0.2 netmask 255.255.255.255 If I ping the alias, if the host I'm ...
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45 views

linux not replying to an arp request

I am running linux 3.14 on a system with 2 interfaces. on the first interface, i can access our local network. on the second interface, arp packets come in but linux doesn't send out reply. is it ...
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60 views

Broadcom NICs, Cisco ASA and ARP request collisions

First of all I am sorry for my english mistakes. Help me please to solve the problem with ARP request collision incidents. I have IBM BladeCenter E chasis with blade servers are installed in this ...
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94 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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92 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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591 views

VMWare ESXi 5.0 Networking Issue

I have an issue with 2 new ESXi hosts. OS - ESXi5.0 Custom Dell ISO patched up to Build 1024429 DELL R820 with 1G network 2 ports from integrated MB NIC(Intel) connected to 2 juniper switches, one is ...
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62 views

Can you SNMP poll the ARP table on Cisco ACE?

I'm trying to get a MAC <=> IP mapping from a Cisco ACE. Unfortunately according to this table, while it supports IP-MIB the ipNetToMediaTable and ipNetToPhysicalTable subtrees are not supported. ...
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139 views

Keepalived, Junos, and ARP caching

I'm trying to configure an active-passive stunnel setup, with the aid of Keepalived, for a public IP address at our company datacenter. I would like to know if a router or switch reconfiguration is ...
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589 views

arp reply is not processed

My eth0 interface does not process a legitimate arp reply. When I try to ping a host, I see arp request and reply with tcpdump from the host I try to ping from, but ip neigh says that there is a ...
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336 views

Cannot ping any machine on local network (embedded linux device)

I have an embedded linux installation (custom built using buildroot, uClibc and busybox) and I am unable to ping any machine on my local network. My /etc/network/interfaces file is as follows auto lo ...
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205 views

stop arp poisoning on a 5448 powerconnect switch

We have to disable arp poisoning on our dell 5448 switch. Right now it has all our production machines running on it and I'm not a networking guy at all so I don't want to run a command that will ...
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118 views

What is the meaning of the QUEUE in arptables

I use the nfqueue target of iptables in order to get packet to the nfqueue and do some business rules on them. iptables -A INPUT -p tcp -j NFQUEUE --queue-num 0 I need to do the same on arp reply ...
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817 views

Arp request is not resolved

On my machine, I have assigned ip addresses for two interfaces which are connected through a cable. They are connected with 10G ports. When i tried to ping the two addresses, ping was not working. ...
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60 views

Server Core DNS Server in VSphere doesn't respond to ping and needs continuous arp clean

I have a VSphere installation hosting two Windows Server 2008 R2 installations. One of them is a complete install that serves as a DHCP server and that I use for administration. The other install is a ...
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313 views

virtualbox bridged adaptor works only guest->host but not host->guest

I have virtualbox 4.1 on a ubuntu 12.04 host. On my host I have a virtual interface eth0:1 configurend as 10.0.1.1. I have a few virtual machines using bridged adapters, configured in the 10.0.1.0 net ...
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304 views

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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5 views

Linux bridge not answering arp packets

I'm trying to setup a test scenario regarding linux bridges for which I need a full virtual IP stack. Basically, I'd like to simulate the network between a VM (or container) and its host, just without ...
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51 views

Cisco ASA 5510 needs “clear arp <Interface>” periodically to reach a single host

ASA 9.0(3) The symptom is that I can ping from the ASA to any other host in that interface's subnet, save one particular host (that host can ping the interface on the ASA however). If I do "clear arp ...
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21 views

How to meet the arp table and the network toology with wireshark

I'm wondering if is possible meet(see) the arp table in a network traffic with wireshark or find some way to build manually the arp table, and how to see the router and swiches of topology( for ...
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37 views

FreeBSD jail loses network connectivity after some time

I have a Jail on a FreeBSD 9.2 installation on my office network, which I use to run some cron jobs that upload and download stuff from external servers. The cron jobs are configured on the main ...
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49 views

Pinging two virtual interfaces(IP aliasing) not working

I have two VMs. I have created a virtual interface on each of the VMs. On VM1: eth0 Link encap:Ethernet HWaddr 06:98:82:00:00:39 inet addr:10.129.34.76 Bcast:10.129.255.255 ...
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180 views

VMWare use of Gratuitous ARP REPLY

I have an ESXi cluster that hosts several Windows Server VMs and around 30 Windows workstation VMs. Packet captures show a high number of ARP replies of the form: -sender_ip: VM IP -sender_mac: VM ...
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38 views

How to fix stalled connection on large download

I have a cisco 1921 router performing routing and NAT function. Cisco 3750 is performing layer 3 core switching duties. Users are complaining about large file transfers being stalled (not dropped) ...
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X520-DA2 10GbE PCIe NIC on Ubuntu 12.04 doesn't respond correct ARP information for a traffic tester

I'm trying to configure stand-alone test network to examine a server that has two 10GbE ports PCIe NIC. But I couldn't get any ARP responses of those 10GbE ports. To execute my test, it's necessary to ...
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27 views

SYN-ACK with identical MACs

What could cause a CentOS machine to respond with SYN-ACK packet having both source and destination MACs set to the address of the NIC from which the packet is being sent?
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44 views

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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113 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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159 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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167 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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47 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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522 views

Trouble directing traffic to Honeyd virtual hosts

I am trying to set up an experiment to observe some network behavior and as part of that experiment I am setting up a closed LAN that has virtual hosts created by Honeyd. I have honeyd running one ...