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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ISP ARP tables and routing [closed]

So I'm Network+ certified and have a beginners understanding of how network communication works, my head starts to split a bit though when I think about how the information is actually communicated ...
user1047228's user avatar
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Is DNS address included in ARP address table?

I have DNS server address 8.8.8.8 . Is it supposed to be included in my ARP table when i execute arp -a?
Χρίστος Κουστένης's user avatar
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Globally raise IP ARP inspection limit rate on Cisco

I am trying to raise the ip arp inspection limit rate from the default rate of 15 on my Cisco 9300 since I am getting to many %SW_DAI-4-PACKET_RATE_EXCEEDED: x packets received in xx milliseconds ...
Rick's user avatar
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Cisco ports shutting down temporally due to arp-inspection

We have a couple of Cisco 9300 switches. We had the switch configured using STIGS. A couple users have complained that their Avaya phones restarted. I started running the show logs and noticed the ...
Rick's user avatar
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Does ARP play any role when we try to access a website?

I was looking to find the role of ARP whenever say we want to access a website like google.com. I found some answers here. But, when I tried to use Wireshark to check the ARP request I wasn't able to ...
Vedanta Mohapatra's user avatar
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Does this DHCP Server need a trusted ARP Inspection port in IOS?

The switch runs Cisco IOS. You want to configure security on Switch 1. The objective is configuring Dynamic ARP Inspection on Switch 1. Which Ports or port will you configure as Trusted? A) None of ...
Atheesh Thirumalairajan's user avatar
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2 answers
101 views

How can a router not recognize a gratuitous ARP MITM attack?

I'm reading the chapter for DHCP Snooping/DAI in the OCG for the CCNA and I have a question regarding how gratuitous ARP message attacks work. I'm sure there is a piece I am missing, but I've searched ...
Alex's user avatar
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Firewall sending ARP requests for 8.8.8.8

We have a checkpoint firewall that is having Internet issues today. When I did a packet capture on the interface going into the ISP router I can see ARP messages for the google DNS servers. Thats not ...
The Footsie's user avatar
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1 answer
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Ethernet frame's source mac-address out of a port in an ARP request forwarded to an interconnected switch towards an end host

PC1 ----- (P1) SWITCH1 (P2) ----- (P2) SWITCH2 (P1) ----- PC2 Assume two network switches SWITCH1 and SWITCH2 are interconnected to each other through their ports P2 respectively present on each ...
Dylan Prost's user avatar
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1 answer
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Arp and flooding

it is my understanding that nodes are not aware of the mac address of other nodes they want to communicate with, when a frame is created to communicate node A with node B, the destination mac address ...
freman1952's user avatar
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Why Linux answers ARP requests for IPs that belong to different network interfaces? [closed]

My machine has a physical network interface (eno1) and a bunch of virtual network interfaces (e.g. tap0). Each interface has its own IP and their subnets do not overlap. I noticed that if I perform an ...
felipeek's user avatar
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what will be fast way of finding the live hosts on network?

what will be fastest way to find the live hosts on network. Currently i am finding the live network hosts using arp request and arp response. I have to find these live hosts every second. Is there any ...
Risen Star's user avatar
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177 views

Trusted and Untrusted ports in DHCP Snooping / ARP Inspection

From a networking course I am following, I've learned that in D. ARP Inspection, ports connected to routers or to other switches should be configured as trusted while the user ports should remain ...
Mitrixsen's user avatar
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Why does the show arp returns a different IP than the PC's gateway on the Switch

I have a PC connected to a switch connected to a router : why does the show arp returns a different IP than the PC's gateway on the Switch ? : PC $ arp -a | grep -w gateway gateway (172.16.15.1) at 00:...
SebMa's user avatar
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Does a router need ARP to send data to router in anther netwrk, it already has the IP address of the interface right?why does it need the MAC address? [duplicate]

i am studying off this https://www.practicalnetworking.net/series/packet-traveling/key-players/#arp but my question is if ip address is for end to end communication , how is the end to end happening ...
Mbaku Baki's user avatar
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2 answers
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How ARP works [Specific Case]?

After reading about ARP and NAT I'm really confused about putting them to work together. Let's suppose we have a router A with a public IP of IP(A). Plus, 2 devices behind that router B and C, each ...
Ori's user avatar
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Are ARP requests cascading

When a device sends an ARP Request, it broadcasts to all Nodes, which then check against their own ARP Tables and respond with an ARP reply or drop the Packet, but what happens if the device is not ...
Alex's user avatar
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1 answer
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ARP and MAC address table

i know that this might be a little academic, but i was wondering. let's assume we have an empty ARP table, and empty MAC Table. let's assume PC A want to send a packet to PC B. is the broadcast frame ...
David Frucht's user avatar
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1 answer
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What could be blocking ARP?

I have a metro ethernet link between two offices with Cisco C3560X's on each end. Actually, I have two links. (We are switching from one provider to another.) I can't get the new link to work. Pinging ...
longneck's user avatar
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How does a router find the next hop when the receiver is in a distant IP network?

Say I want to send a frame to a web server, and let's say this web server is in a very distant IP outside my local network e.g. a Google server. I initially send the frame to my router. My router ...
JohnDoeyyy's user avatar
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Will there be an ARP-Request to a gateway outside the subnet? [duplicate]

This is a question from an exam I don't know the answer to. A client has a wrong configuration: He thinks his only gateway is not in his own subnet and needs the MAC address of the gateway. Will he ...
rwnd's user avatar
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How router will send ARP resolve packet when it receive ARP request?

How router will send ARP resolve packet when it receive ARP request ?? Router by default enabled with proxy arp configuration?? If then proxy arp is not configured then what will happen if it receives ...
G.Balamurugan's user avatar
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1 answer
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How is the destination MAC address filled during MPLS label switching?

During IP packet forwarding, after a LPM(ip lookup) done on the FIB, it will fetch the Nexthop ip address and the egress interface to send out the packet. Now, ARP table lookup is done for this ...
Hemanth's user avatar
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How does ARP work, when the host with known MAC address is moved to another subnet

I've been trying to figure out this for some time, but I'm quite lost. Assume you would have 3 networks -> A (PC0), B (PC1) and C How would ARP behave, if it already knew all MAC addresses from ...
Adrian P.'s user avatar
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1 answer
166 views

ARP cache in firewalls and difference from an end point device

Imagine a device A (192.168.32.5/24). Then two hosts, B and C, connected to the same interface (through a switch) having the same IP address (192.168.32.8/24) configured statically. No fancy tools/...
user2984629's user avatar
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4 answers
1k views

ARP requests from a different subnet

Not sure if my question is on-topic here. I found the following question about ARP requests from a different subnet and I was wondering if and when this is an actual use case. The original question is ...
Albin's user avatar
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1 answer
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How are IP broadcasts handled at lower levels

When I use a broadcast IP address, for example 198.255.255.255, what will happen when it gets passed down to the link-layer which will then look for the corresponding MAC address in your ARP table. ...
Vexea's user avatar
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1 answer
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Is the "ping" command a broadcast message?

I am learning about how ARP works and I have some questions regarding the ping network utility. ping is used to test connectivity and reachability between devices. PCs have their own ARP table where ...
Mitrixsen's user avatar
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ARP Header's Mac Address set to 0 when broadcasting [duplicate]

I'm learning about Ethernet frames and networks and Wireshark has been very useful. I have a doubt regarding broadcasting and ARP request, since we don't know the Target MAC address, in the ARP's ...
ad_valle's user avatar
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1 answer
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Can a host not send a response to an ARP request to remain hidden?

Let's say a malicious host connects to a network. It doesn't wish to identify itself to other devices on the network unless it wants to (eg: for a desired conversation). From what I understand, the ...
user4779's user avatar
  • 115
2 votes
1 answer
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Receiving ARP requests from different networks (cable Internet)

On the WAN interface I constantly receive ARP requests from many different networks. The source MAC address is always the same (MAC address vendor: Casa Systems Inc.). 22:57:57.032541 ... Request who-...
fitcfitcfatc's user avatar
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3 answers
123 views

How to learn IP addresses in a LAN

For communication with machines in the same LAN, hosts do ARP for translating the IP address to MAC address, which means, IP addresses are already known to each other. My question is, how does the ...
Network_starter's user avatar
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1 answer
99 views

The initial ARP cache for a router that never got a packet

I am trying to understand the ARP cache. So, here is the physical structure of my network: Note that I did not ping any of the PCs yet. So, I expected the ARP cache of the router R1 to be empty. The ...
Seif Ashraf's user avatar
4 votes
2 answers
793 views

Why two routers connected via PPP don't use ARP but Ethernet requires ARP?

I have read from @Ron Maupin's answer of this question that your two routers are connected via PPP (this is not uncommon), ARP will not be used , but if the two routers are connected via ethernet, ...
S. M.'s user avatar
  • 378
0 votes
3 answers
297 views

Do hosts in the same LAN know their MAC addresses?

I am trying to learn about how ARP protocol works in LANs. So, here is the physical structure of my network: So, when I try to ping PC3 from PC1, I expected the first packet to timeout because PC1 at ...
Seif Ashraf's user avatar
0 votes
3 answers
475 views

Is knowing MAC needed for talking to another device in same wifi network?

I have heard about ARP protocol for learning MAC address of other devices in a LAN for communicating with each other. However, I am bit confused about how it works in a typical infrastructure mode, ...
Network starter's user avatar
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2 answers
68 views

Client's ARP requests affect whether Cisco C897VA receives packages or not

So I have bought used ISR C897VA with an issue: when vlan1 is pinged from windows there are quite a lot of "Request timed out"s. Config-register 0x2142 has been done, as well as resetting ...
Qeeet's user avatar
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3 votes
4 answers
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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 ...
Aley Hassan's user avatar
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2 answers
1k 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. ...
Avenger.1995's user avatar
-1 votes
1 answer
98 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. ...
AJ HUNTER's user avatar
1 vote
1 answer
226 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 ...
Zee's user avatar
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1 vote
1 answer
145 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 ...
Somayyah Mohammed's user avatar
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2 answers
358 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 ...
Truth's user avatar
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0 votes
4 answers
1k 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 ...
zombiesauce's user avatar
1 vote
2 answers
326 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 ...
shaymin shaymin's user avatar
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0 answers
19 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 ...
JukEboX's user avatar
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0 votes
2 answers
410 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 ...
JukEboX's user avatar
  • 461
1 vote
1 answer
674 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 ...
public wireless's user avatar
1 vote
3 answers
289 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 ...
Azendale's user avatar
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0 votes
2 answers
1k 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 ...
JukEboX's user avatar
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