Hello, and welcome to this Protocol Deep Dive on ARP.
In this module,
we will be covering some of the common problems in networks related
to ARP and how ARP can be used in troubleshooting.
This module will cover what happens when a machine is not on or is
unreachable in the network and how ARP reacts,
this will include a loss of the default-gateway router.
Although this is not a failure of ARP,
it is useful to see how ARP information can be used to assess the situation.
Next, I will show you the cracks in the ARP protocol and processes where stale,
dynamic, and static ARP cache entries cause problems.
You will see how different operating system vendors
implementations handle false dynamic cache entries,
some well and others very poorly,
then I will give you the options for the difficult ones.
You will also see how static ARP cache entries lead to
problems and what would be best practices for when and
when not to use static entries.
We will look next at common problems surrounding proxy ARP.
This will include misconfigurations which create losses of connectivity,
knowing when to use it and when not,
and the overhead it can create in networks and systems.
Lastly,
I often find myself in the situation of not having detailed enough
maps to LAN systems and I want you to see how to use ARP along
with some basic network tools to save your time and solve a very common problem in networking, finding stations in a complex LAN.