Ethertype location

Hey chaps,

Here is my scenario:

Looking at some tasks I often get asked things like this:

Allow only the following Layer 2 protocols across VLAN 146
o STP BPDUs (consider both ISL and 802.1q trunks)
o CDP, VTP, and UDLD
o ARP

Now this requires me to know, or be able to locate the ethertype values.
Being that brain capacity is currently at maximum I would rather look these
values up:

Config wise I know this is referenced via a mac access-list:

*mac access-list extended MAC_FILTER permit any any !ETHERTYPE*

In this particular scenario the values used were:

*permit any any lsap 0x4242 0x0permit any any 0x010B 0x0permit any any
0x806 0x0*

I had no idea where to begin to find these values, are we expected to
memorize these !! :(

So that brings me to the information I am looking to glean from you goo
people:

1. What I am looking for is a path in the DOCS-CD where I can reference
these should I require them. I have found a few links but nothing complete.
Does anyone know where such a thing is?

2. Why do we always set the mask to 0x0, is there a case where this would
be different? (I may have skimmed this part of my studies!!)

\Sam

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Received on Tue Dec 24 2013 - 11:28:15 ART