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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6
votes
3answers
32k views

Understanding ARP and Routers

Let's say there are two PCs, PC A and PC B. PC A wants to communicate with PC B, such as sending a message. I need to describe the arp packets for this task. Known details: PC A -> SW 1 -> Router -> ...
1
vote
1answer
3k views

How hosts will broadcast the arp to Router if there is no default gateway?

Regarding "Why are routers not answering ARP Broadcasts?" As per my knowledge if the target network is different subnet and there is no default gateway is configured the packet will not be ...
5
votes
1answer
898 views

Why are routers not answering ARP Broadcasts?

Host A wants to send something to Host B who is in a different network. Between them is Router 1. Host A sends an ARP broadcast but Router 1 is not answering it. Why is that so?
14
votes
3answers
48k views

On which layer of the OSI Model does the arp protocol belong? [closed]

Can anyone explain which layer of the OSI model ARP belongs to and which socket it uses? I referred to lots of books before asking this question. In some books, Authors are saying that it belongs to ...
3
votes
5answers
19k views

What is the main purposes of ARP CACHE in the Switch?

I know that when a PC send a packets to any remoter router then first of all it checks out the Router MAC address which is connected with it, but it gets this MAC Address of Router from ARP Cache, ...
7
votes
3answers
13k views

What to use as ARP request Target Hardware Address?

When sending ARP request, what must be filled in the target hardware address (THA)? This technet blog post says it is to be filled with zeros (0.0.0.0) -although doesn't look like a MAC address!, and ...
6
votes
2answers
8k views

How ARP works in case of Virtual machine?

As far as my understading goes MAC address is used to recognize a computer node in a LAN where as internet communications happen over IPv4 address. When a request comes from the internet to the ...
2
votes
1answer
4k views

Microsoft NLB - static MAC necessary?

We've implemented Microsoft NLB before, but it's not a common thing for our environment, consequently I've not looked at the config in a while. The topology is: EDGE == 3750X's (stack of 2) == N5K's ...
8
votes
1answer
2k views

Something is filling my force10 ARP table

I have 2 force10 s25 switches that are used for a dark fiber link between two school buildings. One of my switches is filling its ARP table to the brim and then failing. This can happen as often as ...
14
votes
5answers
11k views

Duplicate IP Address - which one wins?

If there's a duplicate IP address, which one "wins"? First, last, flaps, neither?
14
votes
6answers
24k views

What happens when the ARP cache overflows?

In at least one implementation there is a hard limit on the capacity of the ARP table. What happens when the ARP cache is full and a packet is offered with a destination (or next-hop) that isn't ...
18
votes
7answers
12k views

Best practice for the combination of HSRP and ECMP

The combination of ECMP (or other causes of asymmetric paths) and HSRP is broken by default in Cisco IOS; the default behaviour with this design floods unicast traffic excessively. What is the best-...

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