ARP is often considered to work "in between" Ethernet and IP, at layer 2.5 if you will. That's probably what the author means. Though since it does run on top of Ethernet, it can also be considered layer 3.
When you get more and more involved in this stuff it becomes clearer that the OSI layers aren't something to be taken too too seriously -- they can help from a conceptual level, but that's about it. A lot of protocols don't exactly fit into one layer or another. Consider ICMP, for example. It runs over IP, but no one ever calls it a layer 4 protocol. It's generally considered layer 3.5.
[toc:faq]The ProblemOn traditional switches whenever we have a trunk
interface we use the VLAN tag to demultiplex the VLANs. The switch needs
to determine which MAC Address table to look in for a forwarding
decision. To do this we require the switch to do...
[toc:faq]Introduction:Netdr is a tool available on a RSP720, Sup720 or
Sup32 that allows one to capture packets on the RP or SP inband. The
netdr command can be used to capture both Tx and Rx packets in the
software switching path. This is not a substitut...
IntroductionOSPF, being a link-state protocol, allows for every router
in the network to know of every link and OSPF speaker in the entire
network. From this picture each router independently runs the Shortest
Path First (SPF) algorithm to determine the b...