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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Cannot resolve ARP for device on same wifi network [closed]

Here's a simplified network diagram: +--------------+ | Router | | 192.168.10.1 | | 192.168.5.1 | +-------+------+ | | +-------v--------+ +---------------+ | Switch ...
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2answers
53 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
37 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
69 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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38 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 ...
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1answer
35 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
2k 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
52 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 ...
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2answers
149 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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171 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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53 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
43 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
146 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
98 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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1answer
54 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
129 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
54 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
128 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
260 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
203 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
290 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
132 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
50 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
60 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
228 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
82 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
70 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
127 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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2answers
83 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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1answer
89 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
98 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
638 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
25 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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1answer
894 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 ...
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0answers
112 views

Swapping routers resulting in ARP issues? [closed]

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
34 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
377 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 ...
2
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1answer
356 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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1answer
318 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
107 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
45 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 ...
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1answer
370 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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1answer
55 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
55 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
196 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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1answer
824 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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2answers
76 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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