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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ARP broadcast vs Default Route

Assume a host is connected to a router. If a host pings an unknown unicast address that's not in host's routing table, which one of the following is going to happen? (Assume the default route points ...
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2k views

ARP trigger mechanism

I have a question about how an interface triggers the ARP request. For example if two routers have one interfaces each -> (A)[intf1: 2.2.2.1/24] ------- (B)[intf2: 2.2.2.2/24]. If router A ...
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1answer
4k views

What is the difference between ARP and BUM Traffic?

Suppose PC1 with IP address 1.1.1.1 and MAC address A.A.A.A wants to send a frame to PC2 with IP address 2.2.2.2 and MAC address B.B.B.B, plus there is a switch in the middle. PC1 doesn't know where ...
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1answer
472 views

GNS3 v2 router to host connection

I'm trying to make a router inside GNS3 to connect to the host device (a Debian 8) with no success. Am I missing something? DHCP works as expected: ! interface FastEthernet0/0 ip address dhcp ...
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1answer
1k views

ARP requests and multiple interfaces

Suppose a device has both ethernet and wireless interfaces enabled and active. Is it correct that ARP requests from one (e.g., ethernet) cannot reach the other (e.g., wireless) unless a Proxy ARP is ...
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1answer
295 views

Why my computer is making this ARP requests to external (Gov) IP addresses?

I am posting here because I randomly installed Wireshark and I found that for 2 minutes or so (later it stopped) my computer started making ARP requests to IP addresses outside my local network, and ...
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3answers
619 views

ARP Table basics

I'm using the arp -a command to look at the ARP table on my personal computer. After executing the command it shows two types of addresses, dynamic and static. What do the dynamic and static types ...
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1answer
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Juniper ARP table max limit

I'm running EX3300-48T - Junos-12.3R11.2. After binding multiple /24s on multiple vlans on the same switch, Started to notice that the newly and the old assigned IPs are not pinging on multiple ...
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188 views

How does my network interface know which destination IP to ask for in an ARP request packet?

On my VMware internal nat network, when I try to do a simple HTTP request from my guest to my host OS, the arp request from my guest os asks for the MAC address of my host IP and attach it in the ...
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2answers
508 views

Are ARP replies sent directly to the solicitor? [closed]

I understand that most ARP requests are broadcasted to the entire network. What about ARP replies?Are they sent directly to the host asking for the answer? Or must ARP replies go through the router ...
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1answer
1k views

When ARP cache is updated?

Suppose, My host is A A(my machine) has ip address 12. B has ip address 13 C has ip address 14 My machine has below entries in ARP cache B => ip address 13 and its corresponding MAC address C => ...
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1answer
505 views

Reduce ARP cache time-out?

I have active/passive servers cluster talking with another cluster located behind a Router, for some bug in the operating system in the first cluster it did not send GARP message after switch-over ...
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1answer
456 views

Why is my pc not forwarding packets to my default gateway?

I understand that if I were to send a packet to a destination outside my LAN, it would have to reach the gateway first before it is being routed to the final destination. However, when I visit a ...
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2answers
844 views

Specific questions regarding Arp/DHCP

In my Network are: Router Client 1: Victim Client 2: Attacker (Raspberry Pi) Client 3: My Computer (SSH to Raspberry) All Clients are connected wireless to the router. All Clients are registered ...
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1answer
150 views

Switches - help me to understand please

If a PC wants to send to another PC through a switch and does not know its MAC address, that means all PCs on network will receive it and see it!! If we change the NIC for a PC in the network, how ...
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563 views

What will happen Pc1 > switch1 > switch2> PC2

How packet will travel from pc1 to pc2 if there are two switches are in between. PC1 > SWITCHING1 > SWITCHING 2 > PC2 what will be first action arp or ICMP? If ARP comes fast then what is arp ...
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2answers
225 views

ARP reply and use

I have a very rudimentary doubt. I am sure missing something but cant recollect what. Suppose we have 2 hosts connected on 2 interfaces of a switch. if host 1 pings host 2 , it will first send an ARP ...
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1answer
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Cisco HSRP CAM vs ARP timeout

Today we received email from our ISP saying they are performing maintenance on their network so if you have HSRP connectivity with them in that case you need to clear ARP table or reduce ARP timeout ...
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2answers
3k views

Multicast ARP Switch

So a few questions that I've struggled to find firm answers on. 1: Does multicast use arp? So does it ask for a corresponding IP address? I think the answer is no, as it translates the IP to a MAC ...
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3answers
4k views

Endpoint is getting ARP response but not able to ping it/ connect it [closed]

I have a endpoint which is on vlan x and a SNTP server on vlan Y of same cisco switch. I am trying to synchronize my time from SNTP server. endpoint is able to resolve ARP and get the mac of SNTP ...
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4answers
389 views

Overlapping VLANs / Router ARP reply

Hi there, so {unnamed company} has set up some VLSM networks, but they overlap. So network 1 is 10.15.0.0/16 and network 2 is 10.15.208.0/24. Now you can see how these overlap: 10.15.0.1 - 254.255 ...
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2answers
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ARP spoofing in different VLAN

I want to know if I'm protected for ARP spoofing. In my network, all PCs, printers, phones and servers are in distinct VLANs. I got a layer 3 switch for servers, which handles routing between these ...
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1answer
911 views

How does address resolution work with multicast, specifically IPv6?

If I want to send an IPv6 UDP multicast message, how does L3 to L2 address resolution occur? I think I understand ARP and how this same idea applies to unicast, but I am struggling to grasp the idea ...
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2k views

Do we really need ARP when only hubs are used to connect devices?

In the case only hubs are used to connect devices do we need ARP? Packets will be forwarded to every device. So, when a packet whose destination IP doest does not match with the device IP, it will be ...
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2answers
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hp 1920 ARP limit

I am not a network engineer, I have very limited knowledge. background: We currently have a HP1920-48g switch + others around our building. Originally these were "daisy chainned", the new I.T ...
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1answer
130 views

Conflicting of MAC addresses in reply path of direct server response

Consider we are using 1.1.1.1 as our VIP which is the IP address of the load balancer. I'm aware that I should disable ARP replies on loop back interfaces of back end servers. However another issue ...
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1answer
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Can a router send ARP requests to hosts?

I play with libpcap in C recently to create an arp sniffer program that captures arp requests on the air. I came up with a strange effect. I captured arp requests from my router. I don't know if this ...
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280 views

Should a PC populate his ARP table when a frame is not destined to it?

I made this topology in GNS3 : I cleared the switches MAC tables. In this way, when PC1 sends an ARP request to know who has the IP 192.168.1.20 (PC2 IP), the request is broadcast through all ports ...
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2answers
232 views

Why can't the gateway block fake ARP replies?

So here's my understanding of ARP spoofing. I'm malicious, and I want you to think I'm the gateway. So when you ask "if you're the gateway, please reply with your MAC", I reply, "I'm the gateway, here'...
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1answer
69 views

How do computers connected to a Wi-Fi network communicate within the same network?

Let us assume Host A wants to contact Host B. Does it send the packet addressing (IP address of the Host B) and MAC address of router, or does it use ARP to send to the MAC address of the Host B?
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513 views

Arp spoofing and ip detection

I am testing two differents lan and I am tring to sniff traffic with Mitm attack using simple Linux shell command like arpspoof and whireshark to sniff the packets. In the first lan I can sniff ...
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3answers
14k views

When exactly is ARP protocol is used

I am a quite a beginner in network engineering so please be nice. I am not sure I understand how ARP protocol works in some situation. For example, if we have following problem: ARP cache is empty ...
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1answer
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debugging arp requests over vlan

We have a chain of switches configured for vlan 13, let's call them switch1, switch2 and switch3 No, somewhere on this chain the arp requests get lost. I can run tcpdump on these switches. Running ...
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2answers
239 views

More Information from ICMP & ARP

I installed DEKSI Network Administrator Demo and when it is Creating Map, in Step 3 of 4. Searching and selecting hosts for placing on the map, it found IP address and Mac perfectly, but it also found ...
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2answers
952 views

Why I can ping these subnets from a different subnet?

I wonder why I can ping 192.168.3.50 /27 and 192.168.3.70 /27 from 192.168.3.100 /24. Is is not supposed to be impossible? Thanks in advance for your help.
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Would be ARP spoofing attack prevented/limited if switch wouldn't allow for too fast mac address changes on a single port?

So basically, as long as there would be a spare but constant stream of packets, which could only serve a role of securing the claimed MAC address on the switch, wouldn't the ARP spoofing be impossible ...
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1answer
11k views

Why does it show ARPA incomplete?

r-tx-server-1#show arp Protocol Address Age (min) Hardware Addr Type Interface Internet 10.199.0.12 0 Incomplete ARPA Internet 10.199.0.53 0 ...
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2answers
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ARP and DHCP same address to different device?

On my work network, when I go to my DHCP server, then open DHCP > domain_name > IPv4 > Address Leases, I found that 192.168.160.7 is assigned to a iPad device (connected via Wifi). When I use command ...
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1answer
184 views

My pc sends many ARP requests to router over wifi

My pc sends many arp requests to the router over WiFi .. why is that? Also, why does the router send ARP requests to the whole net from time to time?
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1answer
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how are bridges handled in ARP?

assume want to send a packet from H1 to H3 and we have a network like this: **H1** A:a | | N **B1** E --- E:e **R1** F:f--- C:c**H3** S | | B:b **H2** How will ARP table look for these nodes in the ...
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5k views

Why do we need MAC Address if we can uniquely identify each machine with an IP Address

I learnt that in ARP Protocol, to send a packet from one machine to another machine we need to know the MAC Address of the destination machine but since the destination has already been assigned a ...
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1answer
37 views

Cisco gateway and firewall changing addresses?

We have a Honeywell control board that has an Ethernet controller. We have assigned a static IP address as such: IP: 10.2.112.12 Mask: 255.255.254.0 GW: 10.2.112.2 The gateway is a Cisco router. ...
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1answer
228 views

How do protocol stacks determine the destination mac of reply packets?

Suppose a network stack receives an incoming message: Ethernet sees that EtherType is IPv4 so the payload is forwarded to the IPv4 handler IPv4 sees that the IP protocol number is ICMP so the message ...
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2answers
6k views

How do routers traverse packets to their destination?

Sorry in advance for such a noob set of questions. I understand that when set with the task of sending a packet to its destination, a computer first checks that the IP address of the destination is ...
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1answer
1k views

Mikrotik - Cisco requests not working properly

We've got a problem with our WiFi company network. We bought a Cisco Switch and Wireless LAN Controller (Cisco 2500 WLC) plus eight Access Point (Aironet 2700) to offer clients seamless roaming ...
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3answers
6k views

Debugging “no route to host” over Ethernet [closed]

Attempting to connect from a PC to an OpenWRT device over Ethernet is giving "no route to host". I'm working on an OpenWRT port for a new device, so it's possible something isn't configured correctly ...
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2answers
1k views

How does router find a way to host in its own subnet?

I understood that each router maintains an ARP module that stores each client's IP address and associated MAC address. Let's say, there are 512 clients in a router's subnet. When the router gets a ...
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3answers
687 views

Multiple NICs, only eth0 can ping

I have 4 nodes, each nodes have 4 ports. I want connect them without switch like a ring. My topology is looks like: The eth2 and eth3 is down. My problem is, if I am in node2, I can ping node1, ...
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2answers
117 views

Questions about ARP

Windows homelab LAN: How come arp -d does not work consistently? I run the command and the ARP table is not cleared, yet when I run it again a few moments later it does work but leaves certain ...
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1answer
1k views

How to update arp table given a new device?

I have developed a product which provides two ethernet ports. The internal module which manages the eth is a switch with its own mac address that can be modified. To every product I am assigning a mac ...

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