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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Default gateway and ARP confusion

I have the following configuration (I'd post a pic but not enough rep for more than 2): PC1 (10.0.2.10/24) and PC2 (10.0.2.137/29) are connected to a hub, which is connected to a router on interface ...
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15 views

ARP cache getting null mac over a bridge

I have an interface eno1 and a bridge br0 $ ifconfig br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.250.53 netmask 255.255.255.0 broadcast 192.168.250.255 ...
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1answer
43 views

First ping (to any destination) fails from switch but not from router

I've got a basic network setup, just doing NAT to a single public address to an internal /24 without any VLAN's or fancy routing. Both my router and switch are running Cisco IOS 12.x. My ...
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3answers
43 views

Obtain MAC address of remote, unconfigured device?

I have a device that goes on the network. I need it's MAC address. There is no label on it. How do I do that? I have no access to the device itself. I can power it on and plug it in to a switch ...
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36 views

Cisco WAP321 dropping ARP packets

At my office we have 4 WAP321 connected directly to a Cisco 891f router. Randomly throughout the day, computers will lose access to the network. They will remain connected to the Wifi SSID, but can't ...
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19 views

ESX 6 arp fails in back 2 back link

we are having a strange problem with back 2 back connection between an ESX 6 and CentOS 7 machine. Hoping to find a solution on stackoverflow The story is below: - we are using a CentOS 7 directly ...
3
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56 views

ARP behavior in Linux

I have a L3 switch. Port 1 and port 2 of the switch are added to VLAN 30 and an IP address (30.0.0.1) is assigned to it. Port1 and port2 are connected to Host1 and Host2 respectively. Host 1 and ...
3
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36 views

Xen networking - dom0 receives ARP requests but no reachability

Both dom0 and domU are Debian 8. Dom0 network configuration is: auto xenbr0 iface xenbr0 inet manual bridge_ports eth1 bridge_stp off bridge_waitport 0 bridge_fd 0 auto xenbr0.4 ...
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1answer
23 views

Cisco IPv6 Proxy-arp like IPv4

Can I disable the proxy-arp in IPv6 in Cisco? I cannot find the "no ipv6 proxy-arp" command in my Cisco router. Please teach me how to do it. Thanks.
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64 views

Windows 10 arp cache getting stuck after failed attempts when target machines are offline

After upgrading our development team to Windows 10 from 7, we are experiencing an issue with the ARP cache where a machine has the correct IP-MAC mapping cached, but the type is invalid due to failed ...
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24 views

Cisco 2960X & IPDT

I am interested in finding the IP addresses assigned to devices attached to each interface on a Cisco 2960X switch. It seems like IPDT is exactly what I'm looking for. However it seems like the ...
1
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1answer
44 views

ARP Request Being Sent To Different Subnet From Ubuntu Linux

This question is very similar to this one: Linux is sending ARP requests to hosts in other subnets? Main problem - Ubuntu Linux server is sending ARP requests asking for a MAC address of a host on a ...
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24 views

Ubuntu - Destination Host Unreachable Through Router / ARP Requests

Very strange issues on an Ubuntu server running DNS. Here is the network setup. There are two class C network ranges. Let's say they are: 216.107.249.0/24 216.107.250.0/24 Server is assigned an ...
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0answers
36 views

ARP issuse in SUSE Linux

I am dealing with a very strange problem. I have a VM running SLES 11 SP4 in VMware Environment. The machine has two NIC. All of a sudden the second NIC stopped working. It's not even pinging the ...
1
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1answer
40 views

Not sending an ARP request to avoid IP conflict

I am working on Ubuntu. I am setting a static IPv4 for my wireless interface (ifconfig wlan0 192.168.1.2) and connecting to a Wireless Access point and pinging it. I don't see in the sniffer that ...
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110 views

http cookie contains datr not working (none packets is returned) wireshark

When I filter in wireshark: http.cookie contains datr none packets is returned, the list in null. What's I going wrong?
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1answer
61 views

How to make a simple network bridge in Vagrant?

I'm trying do set up the most basic network bridge demo in Vagrant. I have two machines in the same subnet, but on different LANs, and a bridge machine with two interfaces and a network bridge that ...
2
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1answer
59 views

Accessing a server with wrong IP out of segment range

I have run into a similar problem as in this question about a wrong IP in LAN. However, the standard addr alias trick on the NIC did not help. I have no direct access to the server console, I might ...
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75 views

(solved -> bug) forward arp packets as vlan tagged arp packets

How can i forward arp packets as vlan tagged arp packets? e.g. arp packet (no vlan tag) -> eth1 -> eth2.1 -> arp packet (with vlan tag) With the following setup, the outgoing arp packets (on eth2.1) ...
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0answers
16 views

Arp reply on behalf of another devices on Linux

There are devices on a network that don't support ARP (let's name them NARPs) and a device that supports ARP, running Linux (lets' name it LX). LX knows the IP and MAC addresses of NARPs. What is ...
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59 views

why iptables SNAT doesn't help to answer ARP on the vlan tagged subnet?

I'm using iptables SNAT to setup a "router" on a linux box, it suppose to do NAT for 2 subnets. one untagged subnet 10.0.10.0/24, the other one is vlan tagged subnet 172.16.0.0/24. both subnet come ...
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84 views

Ping is happening but arp is not resolved

I am seeing one interesting problem. I have setup two devices connected through lan cable over eth3 interface. Now a vlan session has been created on both the interfaces. Device 2: root@10:~ ...
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1answer
82 views

Why ARP cache is not emptied as I except it to be?

I'm trying to empirically test the time an entry stays in the ARP cache table. This time seems to be defined by /proc/sys/net/ipv4/neigh/default/gc_stale_time file and by ...
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106 views

ebtables arp filtering with openvpn tap interface

I want to prevent arp traffic not destined for the remote side going through a openvpn tunnel so I filter arp requests going to none of my own IPs. Server Setup: /etc/network/interfaces auto br0 ...
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2answers
154 views

Arp request for a non-existing host in a local network

I'm wondering why I get the following result : if I try to access a non-existing host on my local network, for instance using the command ping, I see with the tcpdump arp command that there is every ...
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111 views

What causes the Linux neighbour table confirmation counter to be reset

Given three linux hosts on the same broadcast domain, the sender constantly pings an IP bound to receiver1. When moving the IP address from receiver1 to receiver2 it takes a quite long time for the ...
2
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1answer
70 views

Broadcast ARP query to all nodes?

I am trying to broadcast an ARP query. I want to get every node's ip and mac address updated in my system via this query. So that I can type $arp and see all the nodes on my network and their ...
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0answers
32 views

Wireless devices see ARP replies but not requests, monitor interfaces see both

For the sake of brevity, let's call the wireless interface used for access point (AP) to device communication "wlan0" and the interface used for sniffing in monitor mode "wlan1." In my case, wlan1 is ...
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2answers
84 views

ARP packets are sent as IPv4 packet [closed]

Is it true and why? ARP packets are sent as IPv4 packet. Thanks, in advance.
3
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4answers
237 views

How to find all hostnames (even laptops that aren't currently on the network) on a network?

I manage a network that has a lot of laptops. The users that use the laptops are frequently traveling. When someone gets a new computer I run into a problem determining what the hostname should be. ...
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1answer
64 views

IPv6: I'm confused about addresses [closed]

I'm starting studying IPv6 and I'm having some troubles understanding some aspects. Let's clarify if I'm getting this right! A single host may have: - a unicast global address - a link local address ...
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65 views

MAC address in arp table doesn't match actual MAC, why?

If I connect my laptop directly to the config port of a ubnt airFiber radio I can set a static IP to my laptop and access the default config page to change settings on the radio. When I look at the ...
2
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1answer
125 views

Windows 8.1 Limited Connectivity (on Steroids)

About two weeks ago we performed maintenance on our on-premise infrastructure in our office. Including applying updates to our Hyper-V-based virtual hosts, as well as our SAN. We also modified some ...
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1answer
66 views

Why is there flooding on L2 but not on L3?

Why is it, that on L2 (when there is no MAC Table entry for a new packet) there is MAC Flooding. But at the same time on L3 there is an ARP request (when there is no entry in the ARP table for a new ...
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3answers
358 views

Scanning network devices by mac address

I work in the security devices industry and most of my work relates to IP cameras. Each camera manufacturer has their own software that scans the network for their cameras and gives details about ...
2
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2answers
107 views

New server unreachable for a time after swapping IP address

I am migrating nearly 20 websites from a win 2003 server to a win 2012 server. Both are VMware VM's, on different boxes, but in the same server room, and attached to the same switch. The 2003 server ...
3
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1answer
85 views

Default arp cache timeout

I didn't found how check and change the default arp cache timeout on Linux. I using debian with kernel 3.x (but I supposed it same with older kernels)
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2answers
120 views

arp table entry outside configured network

Can someone tell me why do I have arp table entry outside interface network? Server has 2 interfaces, both on the same network: eth0 10.10.34.146/22 eth1 10.10.33.188/22 ip route default via ...
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212 views

ARP/ICMP in a network environment with overlapping IP address

Currently I have lab network setup to mimic customer's network deployment. (According to the customer, they are using VRF over VLAN so that their customer can have overlapping network connecting to ...
0
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1answer
54 views

Master and slave devices talking to each other through another device with two interfaces. All in the same network

I have three devices, one is a master which will talk with the slave and Device3 but it is only physically connected to the Device3. The slave will speak only with the master(also through the ...
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2answers
79 views

Is turning off ARP a common practice?

I'm just trying to diagnose a problem I and a colleague have had on two separate occasions to swap out an old router with a new one. Both starting from scratch, we've found that we can't seem to ...
0
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1answer
83 views

Polycom VOIP phone seems to mask the secondary device's MAC address from a Cisco switch

When I have a Polycom VOIP phone plugged into a Cisco switch and a laptop plugged into the Polycom phone I get the following. 1) The phone goes into the voice VLAN as expected. 2) The laptop goes ...
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0answers
48 views

Broadcast ARP weirdness

we a running a router on a custom Linux box. Kernel is 3.14.14. What happens is that when you arping the router in broadcast only mode is the router has a verey slow response time: # arping -b -c ...
3
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1answer
115 views

Is it the normal behavior of arp requests?

Sometimes I dive into my network and often I see: tcpdump -n arp 17:59:15.754508 ARP, Request who-has 192.168.1.65 tell 192.168.1.212, length 28 17:59:16.754401 ARP, Request who-has 192.168.1.65 ...
0
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1answer
2k views

How to reverse arp using nping for Windows

I would like to send a reverse ARP to resolve an IP address given a MAC address using nping for Windows. The documentation is not clear on how this should work and I'm unable to find any examples ...
0
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4answers
88 views

Fault tolerance by using two IP with two interfaces

I would like to have a fault-tolerant setup for http requests. For brevity, let's assume we have a very simple Web-service and there is no difference which server responses. So I will have the ...
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1answer
105 views

First Reply on Ping is Unreachable the rest is okay [closed]

please check this weird ping i'm having What may have caused this problem
2
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70 views

arp poisoning and mitm protection [closed]

I'm trying to understand mitm by arp poisoning. To do so I'm practicing on the network I manage: attacker : IPA victim : IPC gateway : IPG I use nighthawk, and kali linux (via virtual box). I can ...
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1answer
400 views

How to troubleshoot internet unreachable periodically through firewall

Periodically the internet is unreachable on my network, sometimes for 30+ minutes. After testing a direct connection to our modem, I realized this was not a problem with our ISP but the network ...
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2answers
1k views

Linux is sending ARP requests to hosts in other subnets?

Setup Host B <--> Router <--> Host A Host A: IP = 192.168.1.10, Net = 192.168.1.0/24, VLAN = 1, Default GW = 192.168.1.1 (Router) Host B: IP = 192.168.2.10, Net = 192.168.2.0/24, VLAN ...