New answers tagged mac-address
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Is ARP a layer-2 or a layer-3 protocol?
ARP is the glue that allows IP to run over Ethernet without pre-configuring mappings from IP to MAC addresess. So logically you could say it fits between layers 2 and 3.
assume I've done this manually
At least on Linux there is no need to do this manually, you can just add an entry to the routing table with the ...
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Is ARP a layer-2 or a layer-3 protocol?
Arguably, it's a layer-3 protocol (due to belonging to the IP core protocols). Technically, it rides directly on top of layer 2, why some call it "layer-2 protocol" which I think is wrong.
does a switch know about the existence of an ARP request, or does all it see is "a frame from a:b:c:d to FF:FF:FF:...
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Switches do forward broadcasts out all ports. They don't care what kind of broadcast it is, and they're unaware of layer 3 information. So yes, they'll forward it. L3 devices, like routers will drop broadcasts. Not sure what you consider "chaos."
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If you send a broadcast ARP request for a host address of a host that is not connected to your network, then the ARP request will simply time out because no host on your network will claim the address. That happens regardless of the address being within your network range or not.
Switches do not know about frame payloads, e.g an ARP request, only the source ...
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frames addressed to a particular machine (ip 192.168.0.20, mac bbbb.bbbb.bbbb) are sent to certain devices in that VLAN.
Unless that MAC address is a multicast address, it needs to be unique in its VLAN - "certain devices" should be "a certain device".
[edit] You seem to be referring to devices attached to the right-hand Nexus - sorry ...
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This is a valid question. Ideally, with IPv6, there is no need for MAC address. However, I believe, following is the reason that it is not being done:
Ethernet protocol needs to be changed - which is a very big deal. At present, address in the frame is compared with the address in the non-volatile memory of the device to receive the data. In ARP protocol, ...
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The mac address-table entries, however, are missing bbbb.bbbb.bbbb.
That is how a self-learning bridge works: it learns the location of nodes by the frames' source addresses and then forwards frames by the destination address based on the learned table.
If the node in question has never send a frame, the bridge/switch cannot know its location and ...
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Each ARP table entry is created or purged on its own. An ARP table entry is created when a host needs to send something to a layer-3 address for which there is no corresponding layer-2 address in the ARP table. An entry in an ARP table will time out and be purged after a period of non-use. It will be recreated the next time the host wants to send something ...
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C also saw A's broadcast message, so it could also add A's MAC
address.
That depends on the OS. By the RFC, C would only update its ARP table if an entry for A already existed in its ARP table.
RFC 826, An Ethernet Address Resolution Protocol -- or -- Converting Network Protocol Addresses to 48.bit Ethernet Address for Transmission on Ethernet Hardware has ...
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I come here from the assumption that wireless communication is just electromagnetic waves, which a network card should be able to decode.
Well, depends on the card. If you're thinking of taking two computers with regular wired LAN ports (1000BASE-T / Gigabit Ethernet, or what have you), then no, it doesn't really work like that. The physics of sending a ...
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Without getting into the physics of it, yes, it's all electromagnetic waves, but unless you use certain frequencies, they don't radiate very far. We have network adapters that are designed for this -- we call them WiFi network adapters. What You're probably using one right now on your phone or laptop.
You can use any medium you like -- cables, radio, light,...
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You can connect two computers with an Ethernet cable and they will communicate (just may have to assign IP addresses manually), or you can have two wireless capable devices communicate if they're in wifi range (this is called an ad-hoc network).
The communication will still probably happen using TCP/IP protocol stack, since this is what most OS's support. ...
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layer 2 protocols use MAC addresses for communication, which doesn't really depend on what network you're in or if you're in a network at all.
Oh yes, it does.
A data link layer (L2) network is required for communication, with an underlying physical layer network (L1: interfaces, ports, cabling) as well. The L2 network doesn't necessarily need to use MAC ...
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I can only rely on the known MAC to determine if the device is here or not
Looking for a MAC address may not be reliable. MAC addresses can be easily spoofed and many wireless devices randomize their MAC address for privacy.
Listening to broadcasts is even less reliable unless the listener is located very close to the access point (WAP). The more distance ...
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can 2 device communicate with each other without data going to physical layer?
No. The physical layer is the one actually doing the bit lifting. Without physically transporting the data to another location there's no communication.
You're forgetting that the data link layer 'only' controls the flow of packets over a local network. Still, the packets need to ...
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I've also encountered this problem two times allready. Unfortunaltely HPE support was not very helpfull. But my mac-learning problems always related to distributed trunking.
My workaround was to step away from dt.
I recommend to use VSF if possible (V3 Modules and zl2 Switch required among other things: https://higherlogicdownload.s3.amazonaws.com/HPE/...
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