From: Earl Aboytes (earl@xxxxxxxxxxxx)
Date: Sun Jan 30 2000 - 03:37:07 GMT-3
I found this on Cisco's open Q & A
Question: Data-link switching (DLSw) permit only Systems Network
Architecture (SNA) traffic through and deny NetBios.
I wanted to double-check the configuration for permitting only SNA
traffic in
the DLSw.
access-list 202 permit 0x0404 0x0001
access-list 202 permit 0x0004 0x0001
dlsw remote-peer 0 tcp 1.1.1.1 lsap-output-list 202
int tok 0
source-bridge spanning
source-bridge input-lsap-list 202
Answer:
Permit SNA Traffic
First we assume all SNA traffic uses service access point (SAP) 4, 8
or C.
binary Hex
0000 0100 04
0000 1000 08
0000 1100 0c
Low order bit of destination service access point (DSAP) (first bit on
wire when transmitted) may be used to indicate an individual/group
address.
Low order bit of source service access point (SSAP) (first bit on wire
when
transmitted) may be used to indicate command/response.
If we define a mask that also allows these bits to be set, it
will look like the following:
Binary Hex
0000 0101 05
0000 1001 09
0000 1101 0D
All of these bit values use a subset of the bits set for the hex
value 0D, so we can define an access list that says the following:
access-list 202 permit 0x0000 0x0d0d
dlsw remote-peer 0 tcp 1.1.1.1 lsap-output-list 202
The access-list uses an 0x0d0d mask to set don't care bits for all the
bits that could be set when representing the SNA SAPs of 04/05,
08/09, and 0C/0D. All other bits must be set to 0 or this filter will
not be matched.
It is not necessary to apply this to both the Token Ring and the peer.
At 11:26 PM 1/29/00 -0500, Ben Rife wrote:
Question:
R1-----R2-----R3
I want to configure dlsw such that Netbios only is allowed between
R1 and R2 and SNA only between R2 and R3.
R2 is a border for the group R1 connects to R2 and R3 connects to
R2.
I know that I need an lsap-output-list (access-list 200) to specify
the protocol type-code right?
Where do you find the sytax for this command/function? Am I on the
right track? Can someone help me?
Thanks, Ben
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