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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Question about ARP requests

When a device tries to associate an IP address with a MAC address for a given device, it sends ARP requests to all devices connected to the same network. If I understand correctly, the searching ...
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2answers
76 views

What does a router do with a packet if it can't find the destination IP address in its routing table?

If a router receives an ARP request in which the destination hardware address is a broadcast address, and if the destination IP address is an address that the router cannot find in its routing table. ...
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1answer
20 views

how does a host learn about other hosts IP addresses connected on the same subnet? [duplicate]

My question is similar to one posted [here][1] But answers are not understandable to me. How can a host (say my laptop) learn about IP addresses of other devices (say my phone) on the same subnet. ...
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1answer
29 views

ARP sending an ARP request on changing port IP address

Using the c7200 images on GNS3. I configured two routers as so: With arp debugging on, after assigning an ip address I see that each router sends a gratuitous ARP response packet (only debug output ...
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1answer
30 views

ARP isn't showing all the interfaces/MAC bindings

I'm playing with Dot1x port authentication, the interface G2/0/2 is connected to a PC and is authenticated/authorized successfully: SW1-2960#show authentication sessions int g2/0/2 det ...
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2answers
55 views

Why does ARP request not use a router instead of broadcast?

Why in ARP request does the source computer broadcast a message with the destination IP address to find the MAC address of the destination computer? Why doesn't it send the message to the default gate ...
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4answers
89 views

What if a host makes an ARP request for an IP outside its subnet?

I have read other similar question on the forum and none have completely answered my question. But to understand my confusion, you would need to know what else I'm confused about. Is ARP a layer-2 or ...
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2answers
54 views

Under what circumstances is the ARP table updated?

Lets say we have 3 devices in the same shared medium : A, B and C. A wants to send a message to B, so before, it sends an ARP request as a broadcast message. When B receives it, it will update its ARP ...
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15 views

Arp Access-List Without An Interface [duplicate]

I have dhcp snooping an arp inspection setup on my VLAN. I have a number of clients that need to be statically set on this VLAN but still plug into a DHCP access port on the VLAN. I have ip dhcp ...
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2answers
66 views

IP Snooping\ARP Inspection With Static Devices On DHCP VLAN

Consider this network: I have enabled DHCP snooping on my system. Switch A has the DHCP connected and the port on VLAN 70 for DHCP has been trusted to allow for reading the database and passing ...
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1answer
76 views

VPN with Cisco virtual ASA on Azure not routing correctly

I've deployed a Cisco virtual ASA in Azure to use as a VPN server. For simplicity, I'm using just the management interface as the lan for the time being (10.2.0.4 is the interface). I want to use the ...
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3answers
56 views

Why do IP(v6) routes require a next hop IP(v6) address and not just a MAC Address?

My understanding of how you "ask" a router to route a packet for you is that you simply put the IP(v6) address of the destination host and the MAC address of the router you are routing via ...
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2answers
110 views

ip dhcp snooping Kills DHCP Ports

I am working on implementing DHCP Snooping on my switches and have found that when I do so it kills the DHCP connection to the clients. The network is as such: The server with DNS is providing DHCP ...
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1answer
23 views

Unable to Communicate from server to other servers after migrating from existing firewall to new firewall

In our existing environment we had migrated old firewall with new firewall after this activity . we had faced connectivity issue . From servers unable to reach other servers . Post clearing ARP table ...
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1answer
25 views

issue regarding broadcast mac address

I read a line saying {Routes do not forward packets coming from one interface having broadcast mac address (FF:FF:FF:FF:FF:FF)} what is meant by one interface in that line? if router cannot broadcast ...
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0answers
88 views

EVPN+VxLAN strange silent host issue

EVPN+VxLAN very strange silent host issue I have very basic EVPN+VxLAN design where i used OSPF/Multicast/BGP/vPC technologies to build small size datacenter. L2VNI working great without any issue. I ...
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2answers
35 views

Broadcast times for new devices in ARP protocol

How many broadcasts are needed in ARP protocol for one new device send to another new device to get necessary ARP table entries for lookup in one switch?
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1answer
102 views

Suspicious flood of ARP requests [closed]

I'm trying to review a Wireshark capture and it seems the network is heavily flooded with ARP requests that make no sense to me. The destination is not "Broadcast", but some unknown DELL ...
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2answers
70 views

What role is ARP playing for a internet request?

For me it is not clear how the internet is working. Let's say we have host (local IP:192.168.12) and the gateway/router (local IP: 192.168.0.1 / extern IP: 62.1.2.134) Now the client (192.168.0.12) ...
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0answers
11 views

ARP Table Entry [duplicate]

There are 2 devices - A & B in a LAN. They have no entries in their ARP cache. Device A sends an ARP request to know the MAC address of device B, considering that the ARP request does not have an ...
1
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1answer
67 views

How does router know MAC addresses of computers that are connected to a separate switch? [duplicate]

i am a newbie but i need to understand this ARP thing. In my company we have a router that has 3 switches connected to it. On the switches there are more than 100 hosts. I know that switch learns and ...
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1answer
44 views

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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2answers
135 views

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 ...
3
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1answer
302 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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2answers
93 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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1answer
38 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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1answer
33 views

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 ...
2
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1answer
433 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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3answers
205 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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2answers
88 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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2answers
80 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
31 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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0answers
23 views

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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3answers
90 views

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
77 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 ...
2
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2answers
97 views

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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2answers
91 views

Question on ARP

I'm not really sure if the IP-MAC addresses for the router get stored in the ARP cache of endhosts, hence the question.
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2answers
138 views

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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1answer
46 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
143 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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0answers
51 views

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 ...
1
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1answer
87 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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5answers
3k views

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
59 views

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 ...
3
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2answers
823 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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0answers
16 views

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 ...
2
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3answers
437 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
152 views

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
49 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
173 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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