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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Ubuntu Linux - multiple NICs, same LAN… ARP responses always go out a single NIC

We've got AT&T U-Verse internet service, which has an extremely boneheaded DSL gateway. We have 5 IPs (netmask 248), but the gateway is incapable of doing anything other than a single IP -> ...
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Why is a ping response being sent to the wrong gateway?

In a previous question, I was trying to determine why my OpenVPN clients could not ping the server LAN, even though the server LAN could ping the clients. Having investigated this further, I ...
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Is it possible to match an internal IP address to a switch port?

I'm trying to find a computer that has a certain IP address on our internal network. I have identified the computer name from DNS, but in this case it does not help me. Just wondering if I can ...
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1answer
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Ubuntu Linux - two interfaces, same subnet, different vlan - MAC/ARP issues

I'm attempting to setup a server that needs to have interfaces on the same IP subnet, but different VLANs: eth1.102 Link encap:Ethernet HWaddr 00:50:56:b1:00:0f inet addr:10.1.1.6 ...
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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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3answers
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How to broadcast ARP update to all neighbors in Linux?

Some clients in the subnet has cached the IP with old MAC address, I want them to update the new value by doing a ARP broadcast, is it possible in Linux?
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3answers
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How to configure remote access to multiple subnets behind a SonicWALL NSA 2400

I have a client that uses a SonicWALL NSA 2400 as their firewall. I need to setup a second LAN subnet for a handful of PC. Management has decided that there should be a second subnet even though ...
4
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1answer
769 views

Cannot ping B from A until B pings A

I have a server cluster all connected on a local network(all physical machines, not virtual). When trying to ping from Server A to B, I get a Desitination Host Unreachable. I can ping from B to A no ...
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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
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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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2answers
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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 =...
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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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1answer
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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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3answers
807 views

Best method and tools for local IP scanning [closed]

I’m starting to administer a small but confusing und badly documented local heterogeneous network (mostly Windows workstations, printers, laboratory equipment, etc. and one Linux/Samba Server) (192....
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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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3answers
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ARP broadcast and router performance

My employer subscribes to a fiber based leased Internet from a publicly owned incumbent ISP. The ISP admin says that he cannot give a subnet bigger than /30 because he fears that the ISP edge router ...