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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Much ARP requests from Cisco ASA 5510

An employee of the ISP writes to me that a lot of ARP requests from us go to them. ISP equipment log: 07:47:27.732242 ARP, Request who-has AAA.BBB.CCC.213 tell AAA.BBB.CCC.53, length 46 07:47:27....
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How does the ARP table know to update if two hosts flop IP addreses?

When hosts on the same local network communicate, they manage their own ARP tables which translate between IP addresses and MAC addresses. Thus when computer A needs to send data to IP address ...
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278 views

ARP Router issue

I have a question when a Router receives ARP request to a host that dosen't exists on the forwarding table for that router does the. And this Router is not the next hop either will the Router continue ...
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57 views

Intermittent Network Performance Problems

I've been dealing with an intermittent issue in my network for several weeks now. Symptoms: Periodic "Destination host unreachable.", and similar errors when pinging. The following is ...
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27 views

IP datagram route through a network utilizing ARP

Suppose I want to send an IP datagram from node D to node C . Each step I also want to list the MAC addresses of the source and the destination , as well as the source and the destination of the IP ...
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How might ARP impact the UDP communication and what is a scenario i can reproduce to check/understand it?

I was wondering which impact the ARP protocoll might have on a UDP communication. I am learning for an exam and trying things out with mininet (linux )/ wireshark to understand the dependencys between ...
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1answer
72 views

How to capture mixture of packets with and without VLAN tag over LACP with tcpdump?

Given following configuration in Linux: bond0 in LACP (802.3ad) mode with two VLAN networks running over it. bond0.111 configured with static IP bond0.222 configured with DHCP How to capture packets ...
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2answers
45 views

Why is in all arp table snmp oids an interface index before the ip number?

When I want to get arp information about a single ip number or subnet, I have to snmpwalk the whole arp table, as some oid architects had the "great" idea to always insert an interface index ...
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29 views

When traffic is intiàted from pc is ANDing process or ARP process start working first

When traffic is initiated from desktop which process starts first; the ARP process or ANDing process?
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41 views

Is the outgoing interface of a router in the same Subnet as the Incoming interface of the NEXT HOP router?

In the TCP/IP Volume 1, it is stated that ARP works only on the same subnet. Does this mean that the outgoing interface of a router is necessarily on the same subnet as the incoming interface of the ...
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1answer
25 views

Who can get ARP packets? [duplicate]

I'm new to networking. And as far as I understand about ARP messages, Alice can only send ARP to Bob if two are connected. But if Alice and Bob are connected to a router, but not connected to each ...
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MAC flooding for new host in L2 domain [duplicate]

This hypothetical network has one dumb L2 switch and two hosts A and B connected to it. CAM table entries on the switch are all populated and both hosts have ARP entries for each other. Now if a ...
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How are packets ( received from the server ) sent to the host from the gateway ( which is present in the host network )?

If the host is receiving packets from a server, these packets have a destination IP address of the host and it is first received by the gateway present in the host network. Now the gateway checks the ...
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1answer
37 views

Broadcast ICMP and gratuitous ARP

When sending an ICMP broadcast, all nodes can respond. is it the case of the sender too? If it's the case then: Is it specified somewhere that the sender should respond with gratuitous ARP when the ...
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2answers
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Can a switch send a frame back to the source host because of a loop?

First, I understand how switches work when they receive a broadcast frame. They will record the source MAC address on the incoming port (put it in the CAM table) and then flood the broadcast frame out ...
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Question on ARP

Given the above diagram, is it correct to say that the ARP cache table in PC A contains the IP-MAC addresses for PC B and the router, while the ARP cache table in PC B contains the IP-MAC addresses ...
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ARP-Request - Reply from the perspective of a router

Presume I have a route table with such entries: typedef struct route_table_entry { uint32_t prefix; uint32_t next_hop; uint32_t mask; int interface; } route_table_entry; I have a ...
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42 views

ARP protocol, how it should behave [closed]

I am trying to implement the ARP protocol by myself, but I'm not sure how it should behave, how I should craft an ARP request. How does it work and why it should work.. I tried to research this on ...
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1answer
85 views

Wireshark does not capture free arp packets (opcode2)

Wireshark does not capture free arp packets (opcode2). Only arp announcement packages (opcode1). While running wireshark on the windows 10 computer, I turned on the other computers, but wireshark does ...
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Arp Protect in dynamic VLAN environment

I am using 802.1x authentication with dynamic Vlan assignment(CPPM). As you may know, when a user logges in to their computer, SW attaches the user port to related Vlan. Thinking the scenario in which ...
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1answer
40 views

How does the swtich know if a packet needs layer 2 switching or layer 3 routing?

I have a network topoloty as follows A --------- B --------- C /|\ /|\ /|\ / | \ / | \ / | \ A1 A2 A3 B1 B2 B3 C1 C2 C3 A, B, C are ...
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How does a host in one subnet know to forward the packet to the router MAC, when trying to send a packet to another subnet

I am trying to understand the ARP protocol and I could not understand the above. Consider the topology as follows: H1(1.1.1.1) - (1.1.1.0)R(2.2.2.0) - H2(2.2.2.2) My understanding is that if the ...
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1answer
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How is traffic correctly routed in Site-to-Site VPNs where all sites are on the same subnet?

http://rockhoppervpn.sourceforge.net/ref_site2site_bridge_6.html The diagram on this page shows all 3 sites using the same subnet, 192.168.0.0/24. Let's say on the hub site where 192.168.0.10 is the ...
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2answers
322 views

What's the difference between “show arp no-resolve” and “show arp” in Juniper?

What's the difference between show arp no-resolve and show arp? If I add the no-resolve, what's the difference of it?
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ARP traffic for devices in same LAN but different subnets [duplicate]

Given a LAN with 5 devices (a,b,c,d,e). Where devices a and b are in one subnet and d,e,f are in another. Will an ARP request broadcasted by a looking for device b reach devices d, e ,f as they are ...
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242 views

Will pinging the multicast “all hosts” IP 224.0.0.1 fill my ARP cache with all hosts on my current subnet?

Just wondering in case I ever have a want / need to see all the hosts on my subnet.
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1answer
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ARPs in WIFI Interface Monitor Mode

I set my WIFI interface to monitor mode. I did not expect to see any ARP requests. Can someone explain why there is ARP traffic?
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1answer
45 views

Packet analyze on router does not match client and server

thank you for your time. My (virtual) network has 3 objects : a client, a server and a router between them. I'm sniffing the traffic on the 3 machine with the command tcpdump -i any -s 0 -w [path] ...
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1answer
153 views

How to get IP address of device from its MAC address on network?

Though it seems possible duplicate of this question. But the need to ask this question again is to simplify the scenario and the demands to just finding the IP address of the device. The network in ...
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1answer
148 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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83 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
138 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
57 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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191 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
751 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
354 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
354 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
269 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
152 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
64 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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1answer
508 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
137 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 ...
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1answer
119 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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1answer
170 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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Is this wireshark capture showing any issue? [closed]

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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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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1answer
156 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
144 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
823 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
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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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