Questions tagged [arp]
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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Make Linux reply to certain ARP requsts
I’m trying to pull a certain routing stunt where I want my Linux server to respond to arp requests for 10.0.0.1 on eth0, although
10.0.0.1 is not the configured IP for eth0 (in which case the kernel ...
3
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Ping problems with two interfaces, same subnet, direct connections to two separate hosts
I have a configuration of a client machine (Ubuntu 14.04.2 LTS) that directly connects to two server machines. The server machines--while on the same subnet--cannot route to each other. Packets must ...
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When do STALE arp entries become FAILED when never used?
root@openwrt:~# ip -s -s -4 neigh show dev lan
10.64.42.121 lladdr b8:20:00:00:00:00 used 6387/6341/6313 probes 1 STALE
10.64.42.157 lladdr b8:20:00:00:00:00 used 24/813/19 probes 1 STALE
10.64.42.12 ...
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iwconfig and arp commands report slightly different MAC addresses
I'm at a wifi hotspot where, when I look up the router's MAC address by two different methods, I get slightly different results:
$ arp -a
? (10.128.128.128) at 00:18:0a:58:WX:YZ [ether] on wlan0
? (...
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1
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sudden increase in arp entries when i rlogin from one node to another node
when I r-login from my one host to another, I am observing sudden increase in arp entries from 80 to 900. and this is causing neighbour table overflow. can anyone suggest why this is happening??
...
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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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1
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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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2
answers
407
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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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1
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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 ...
2
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0
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ESX 6 arp fails in back 2 back link
Having a strange problem with back 2 back connection between an ESX 6 and CentOS 7 machine.
We are using a CentOS 7 directly connected to ESX and we use it as iSCSI NAS - from time to time the ESX ...
3
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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 ...
2
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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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1
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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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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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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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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 ...
1
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0
answers
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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 ...
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1
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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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1
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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 ...
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1
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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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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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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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1
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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 /proc/sys/net/ipv4/route/...
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2
answers
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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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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 ...
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1
answer
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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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2
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ARP packets are sent as IPv4 packet [closed]
Is it true and why?
ARP packets are sent as IPv4 packet.
Thanks, in advance.
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4
answers
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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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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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0
answers
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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 ...
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1
answer
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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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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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4
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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 ...
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2
answers
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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 ...
13
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2
answers
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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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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 10.10....
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0
answers
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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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1
answer
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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 Device3)....
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2
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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 ...
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1
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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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0
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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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1
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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 ...
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1
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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 ...
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4
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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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1
answer
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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
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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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1
answer
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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 itself....
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3
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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 = ...
4
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0
answers
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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 ...
1
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0
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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 ...