From: Simon Baxter (Simon.Baxter@xxxxxxxxxxxxxx)
Date: Mon Aug 21 2000 - 04:17:28 GMT-3
Hi Devinder. I often find the older IOS docs are a bit 'fuller' on these
kinds of access controls - have a look at the following link on the CD (if
it works!!)
http://127.0.0.1:8080/cc/td/doc/product/software/ssr90/rpc_r/54037.htm#xtoci
d326145
If you can't link to it, it's the SRB on ver 9.0 which has some info on
LSAP, Type and access-expressions.
Also, I found this in the docs :
http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/3303e/softwar
e/bctb.htm#xtocid1911516
You can filter Ethernet- and SNAP-encapsulated packets on input. For
SNAP-encapsulated frames, the access list you create is applied against the
two-byte TYPE field given after the DSAP/SSAP/OUI fields in the frame. The
access list is applied to all Ethernet and SNAP frames received on that
interface prior to the bridge learning process. SNAP frames also must pass
any applicable IEEE 802.2 DSAP/SSAP access lists.
You can also filter IEEE 802-encapsulated packets on output. SNAP frames
also must pass any applicable Ethernet type-code access list. The access
list you create is applied just before sending out a frame to an interface.
The last line says that SNAP packets will be parsed through 802.2 DSAP/SSAP
ACLS and Ethernet TYPE access lists.
hope this helps! I've got 2 weeks today until LAB...
-----Original Message-----
From: Devinder Singh [mailto:devinder@collabria.com]
Sent: Sunday, August 20, 2000 2:43 PM
To: 'ccielab@groupstudy.com'
Subject: Access Lists - Non-routable traffic
Hello once again..
I apologise for posting multiple questions on this list but for my LAB
exam.... It's a pain..
Caslow's Chapter on Access-lists for non-routable traffic is really
confusing and I am not even sure if it is sufficient for Lab exam. It is
somewhat hard to understand it. Specifically, I have not been able to grasp
anything on LSAP and type access-lists and dont have any
implementation experience on them too.
Can somebody please explain what the difference is between the two and which
one to apply where. Like when and where would we use type-list and
lsap-list (input and output)
Although I am not sure, but I think they are based on the frame types
passing through interface. May be like if it is Ethernet_II or 802.2, then
LSAP is used and if it is 802.3 may be SNAP, then type code is used (I can
be very wrong). Can it be clarified please ??
I also read somewhere in DOC CD that if access-list with type code is used
is used, all the 802.2 frames with LSAP are still subjected to that
access-list as there is a type field in those frames.
This all is a big confusion............. May be a right document on CD can
help if someone can point out.
Any help would be greatly appreciated,
Thanks in advance..
Devin
San Jose .. 2 days
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