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Questions tagged [arp]

For questions about Address Resolution Protocol (ARP). ARP resolves OSI layer-3 addresses to OSI layer-2 addresses.

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19 views

Arpping responding with Cisco ASA interface mac address and mac address of machine

For some reason our Cisco is responding to arp requests between machines on the same switch. It's not breaking anything but it is slowing initial connections. I've been making a lot of changes on the ...
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2answers
250 views

How can i monitor ARP packet on WiFi network?

I want to monitor packet in my network. It said that ARP packet request broadcasted all over network. But why i only see my arp request packet and reply packet to the gateway?
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1answer
33 views

what are Hardware size and protocol size in ARP header? Attached image

While working on packet capture for a simple scan, just had a look at packet capture and want to know what does hardware size and protocol size means in a ARP header?
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1answer
99 views

Getting lot of unwanted broadcasts on my network

I am pretty new in Networking (noob), while I was monitoring my network using Wireshark, and I found that there is a lot of broadcasts happening all over the network, broadcast on Local network ...
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1answer
49 views

How data travel from a node to a destination IP address? [duplicate]

Let's say I have a lot of devices which connect to a single switch, and the switch itself connects to a router which provide Internet connection. Whenever an application on a node needs to ...
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1answer
25 views

Why we need Mac address to send Packets? [duplicate]

While sending a packet network layer attach the source and destination Ip addresses to it. But Data link layer need a destination Mac address in order to send the data through router or within a ...
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1answer
85 views

What is passive ARP learning and how does it work?

Is it the same thing as gratuitous ARP? I cannot find any good sources on the topic.
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1answer
120 views

Cisco DAI / arp inspection limit

During a recent penetration test it was found that we didn't have dai set quite as tight as possible to fully stop things. I'm running Cisco 3750x if it matters. The interfaces are configured with ...
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1answer
63 views

How the broadcast MAC address accomplished?

The Layer 2 broadcast is the destination address of the Layer 2 package is FF-FF-FF-FF-FF-FF. I have a question about the broadcast MAC address. you see the ARP request, it send the destination MAC ...
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1answer
58 views

Devices in same vlan cannot ping each other - ARP Issue [closed]

The environment is running with Nexus 9K in NXOS mode. Both are in vPC mode and running hsrp with N9K1 active and N9K2 standby. Due to vPC both nodes are running Active/Active for HSRP. Now the ...
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1answer
87 views

ARP spoofing over WLAN

As I understand, in ARP spoofing (of any kind), there's a man in the middle that intercepts frames from a sender (Alice) by masquerading as a receiver (Bob) and passes this frame to the server by ...
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1answer
35 views

Prevent Users from Setting Specific Static IP

I have an HP procurve switching environment in which users are often assigned static IP's. One user changed their IP to 172.17.1.1 which is the core switch VLAN 10 interface. Since all the users in ...
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1answer
53 views

ARP source address behind a switch

I have an ECU sending ARP request to another ECU destination and it's working fine. the problem arises when I use an automotive switch in between. the source IP address is 192.168.0.12 the switch ...
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2answers
36k views

How to send an ARP request manually? [closed]

I recently sniffed with Tcpdump a packet "ARP, Request who-has 192.168.2.3 tell 192.168.2.2, length 28". I would like to reproduce this message, and to send an ARP request from my laptop to any IP I ...
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1answer
70 views

ARP after DHCP discover

Hey All, I was working on DHCP lab As seen in the below figure when I take a pcap between e2 and R1 [in a situation where i shutdown the f0/0 interface on R1 and startup again] I see an ARP ...
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2answers
57 views

Sending ARP query message to another subnet

Host E would like to send some data to Host B. Further assume that Host E doesn't have Host B's MAC Address. When the router is present between sub net 2 and 3 no ARP query message is send but when ...
5
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1answer
14k views

Sonicwall NSA 2600 routing issues with multiple LAN interfaces configured

We have a Sonicwall NSA 2400 that has been in service for some years now. We've never had an issue with any routing until we "upgraded" to a new NSA 2600 device. Below is a rough idea of the ...
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1answer
49 views

Is there a way of Juniper to avoid the vast ARP requests?

In my Juniper router the interface always send ARP requests for some non-using IP address. Is there any issue there? and whether there is a way of Juniper to avoid the vast ARP requests? Is it ...
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3answers
4k views

If there's no response to the ARP request, will the host send to its default gateway?

Host A and B are on the same subnet. A sends ARP request(s) asking for B's MAC. For whatever reason, B doesn't respond. Will A either: Give up -- it can't reach B Send the packet to the default ...
4
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1answer
103 views

How do ARP requests work

So I may have a stupid question that mainly comes from me getting weird results to say the least while experimenting. I'm a bit unsure how do ARP requests work. For example how can I arp my entire ...
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0answers
45 views

Is this wireshark capture showing any issue?

I used Wireshark to capture the packets bellow: ... 350 18.942762436 d0:07:ca:0b:63:0c -> Broadcast ARP 60 Who has 13.210.32.75? Tell 13.210.32.78 351 18.947224197 d0:07:ca:0b:63:0c -> ...
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2answers
77 views

Why can't we have duplicated IPs?

This may be a really dumb question, but I like to turn upside down what I already know sometimes, that way I can learn more. For example, given a network 192.168.0.0/24, I have a device inside with ...
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2answers
159 views

Which MAC should be used: device MAC or Interface MAC?

My L3 switch has ~30 interfaces. If you look at the output below there are two MAC addresses showing in the results of the show interface command. The hardware address is the same for all interfaces. ...
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1answer
32 views

ARP table updated when receive message

I'm studying networking and I have a question about when an ARP table should update. Consider this scenario: Host A has the MAC address of host B in its ARP table. Host B's ARP table is empty. ...
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1answer
44 views

ARP behaviors between hosts connected via switches

In a scenario like the following, where different hosts are connected via switches only, I'm not sure how the ARP packets will look like when A wants to send an IP packet to B. I assumed all the ...
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1answer
487 views

Why would a switch ever send an ARP request for a MAC address when it can just wait for the first packet to be received from a device?

I've been reading 'Windows Networking Fundamentals' and in that book it says that a switch can learn what MAC address is associated with a particular port when the connected device makes its first ...
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1answer
24 views

Sending Frames Among Routers needs MACs?

Following this discussion: ARP request outside of LAN; Target machine or router response? I'd like to understand if router 1 sends its frames to router 2 through the same ARP process as discussed ...
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0answers
69 views

Swapping routers resulting in ARP issues?

A day ago I tried to swap out a router with a Meraki MX-84 Gateway in order to test the Meraki's VPN functionality. I set the static IP configuration on the MX-84's Internet interface to be the same ...
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1answer
311 views

Is there a way to capture only gratuitous ARP's using tcpdump?

I'm trying to set up tcpdump to filter only gratuitous ARP's. I know that I need to search for packets with a host set to ff:ff:ff:ff:ff:ff. And I found the arp.opcode parameter, but I can't seem to ...
2
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1answer
32 views

Why the ARP packet contains values like “Physical Address length” etc?

From what i know,MAC addresses are made of 48 bits,while IPv4 addresses are 32 bits Why are there these header fields? Are there MAC addresses with more or less 48 bits?
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2answers
206 views

No route to host for IPs in same subnet being routed by bgp

I have set up BGP to do some custom routing for a subset of addresses in the range 192.168.1.0/24. I have verified that the BGP is working by testing ping/curl on a different host in a different ...
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2answers
790 views

ARP table is not updated with NMAP

Here is what I do and what happens : Let assume I have a device A with IP X.X.X.200 connected to the network I use Nmap to ping my local network, with the command "nmap --send-ip -sP 192.168.1.1/24" ...
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1answer
136 views

Virtual IP failover issue with vmware exsi ip based hashing

We are deploying HA database cluster on exsi which based on virtual IP concept for failover. if One node fail reserved VIP will be assigned to another node we have two exsi nodes and two virtual ...
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3answers
55k views

How does a switch learn a switch table?

Say the switch table is empty. If computer A sends a frame destined to computer B, the switch will broadcast asking who has the mac address of B. What if C suddenly sends a frame to A? What is the ...
0
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1answer
110 views

How can a Juniper Router update its arp table?

I know the ARP table is cached data. On Juniper, we can use show arp to query the arp table: admin@juniper> show arp | match "16.23.43.75" ac:1f:6b:90:d1:ca 16.23....
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1answer
79 views

On a 3560E Switch

** Attempting to view IP address of a Non-Cisco device connected to the switchport. Already entered show mac address-table int gi0/35. Got the mac, then tried the sho ip arp vlan 120 | include ...
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1answer
36 views

Whether the ARP table is based on IP or Interface?

Is the arp table based on IP or based on network interface? I have a VM, it has an Interface with 10.211.55.7, when I show the arp, it shows: I want to know if the ARP table data is divided by IP or ...
36
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3answers
108k views

How does gratuitous ARP work?

Does gratuitous ARP work like a normal ARP request? Why is gratuitous ARP used for HSRP?
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1answer
219 views

Arp Cache Timeout [closed]

I'm trying to poll the arp table from a backbone switch but i want to understand which records are up. I just want to know if there is a specific time for the switch to keep a record on the arp table ...
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0answers
62 views

Wireshark switch ping

I understand that a switch will broadcast to all ports if it doesn't have the destined destination in its mac address table but when I analysed a scenario in wireshark I got confused at what happened. ...
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1answer
29 views

How does a system know the local gateways MAC address for given IP address [duplicate]

Assuming you have the following network structure. Knowing the IP address of the WWW-Server, system A wants to send an IP packet. As I understand the destination MAC address has to be in the same ...
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1answer
50 views

switch wireshark arp

I connected 4 pcs to a switch, I used pc 1 to ping another pc(pc 3) and used wireshark on all the pc's. The one that sent the ping sent out an arp request and received 4 request and replies from the ...
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2answers
117 views

Please help me understand this simple arp request / reply - how does a router know an IP address without knowing the MAC address?

I am new to networking, I am using Wireshark on my home PC to learn about ARP. I understand that ARP is used to build the ARP cache, which correlates IP addresses to MAC addresses on a LAN. ARP ...
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4answers
2k views

Does every host on the LAN share the same ARP table, or do hosts keep them individually?

I'm just learning about ARP. I'm a little bit confused. My confusion is better explained in a scenario. Host A is communicating with Host B. Host A knows Host B's IP address, but not it's MAC address....
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2answers
73 views

How does a computer know IP address of a computer on another network

I was watching a video explaining ARP, which was explained really easily but I got confused when they said that Host A already knows Host D ip address which is on another network. Host A and B were ...
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1answer
396 views

MAC Table vs ARP

I understand that for a switch to learn a MAC address, if host A wanted to send data to Host B the switch learns host A MAC and places it in the MAC table. If it doesn't know where the MAC (for Host B)...
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4answers
1k views

Should I receive an ARP reply from a host that is logically on a different subnet but is connected to my host via a hub?

Host A: 128.238.66.100/16 Host B: 128.238.67.100/24 The hosts are connected to the same hub and nothing else is connected to that hub. The routing and ARP tables of both hosts are empty. Host A ...
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0answers
19 views

ARP and OSI model layers [duplicate]

Is ARP Layer 3 or Layer 2 protocol? It is used to figure out destination MAC, which is a second layer address, however, it has the info about destination IP address, which is a third layer address, ...
2
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2answers
145 views

How does a router know the destination mac?

so if I send a packet from a host to another from the same network we know the mac address of both the source and destination. However if the receiver is in a remote network the destination mac ...
0
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2answers
43 views

What is the bridging decision when getting ARP request?

Setup: Assume I have 3 VMs. VM1 VM2 and VM3. VM2 has two interfaces, say eth1 and eth3. eth1 is connected to VM1 physically and eth3 to VM3. I create a bridge on VM2 using brctl with eth1 and eth3. ...