Another DOCSCD & Eth-mask 0x0






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 0x0

permit any any 0x010B 0x0
permit 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!!)

image

Sam

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