about ARP protocol stack?

I was reading Network+ N10-005 by Craig Zacker, and saw very interesting explanation about ARP. The ARP works within Data-Link layer, however ARP messages aren't carried within TCP/IP datagram.

question where does ARP stack belongs to?

thank you guys for your time

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--chris--

sys_teck wrote: »

I was reading Network+ N10-005 by Craig Zacker, and saw very interesting explanation about ARP. The ARP works within Data-Link layer, however ARP messages aren't carried within TCP/IP datagram.

question where does ARP stack belongs to?

thank you guys for your time

Ill participate in this only because I need help with all of it

I believe this belongs to the next layer up above Data link, the network layer.

Now someone that knows, please confirm!

EdTheLad

ARP sits on top of the datalink layer. Look at an ethernet frame, it has a type field, this type field specifies how to handle the next header. ARP is indicated by a type field value 0x0806. When a device receives an ethernet frame with this type field it knows it has received an ARP frame. IPv4 uses the type field 0x0800. ARP is between L2 and L3, call it layer 2.5 , these protocols don't always fall nicely into the osi model, in your exam choose L3.

docrice

My answer is that ARP stands in L2 since there are no routing functionality built-in like L3. That said, the exam itself might be looking for a different answer due to context and its own interpretation.

This situation is sort of akin to "where does ICMP sit in the protocol stack?" Some say L3, some say L4, and I say L3.5 since it rides over the IP layer, but it doesn't involve a port which ultimately gets used by the TCP/IP stack to funnel the data up to the upper-layers.

EdTheLad

ARP, no routing, but it has ip address fields in it's header. Safer to go for 3 in an exam, but only you can decide what to choose

Trifidw

IPv6 doesn't use ARP either.

sys_teck

Thank you EdTheLad and docrice for clarification.

sys_teck

Thank you Chris for reply