From: Fred Ingham (fningham@xxxxxxxxxxxxxxxx)
Date: Thu Nov 29 2001 - 14:48:20 GMT-3
Brian: From a previous post (edited):
The last bit of a SSAP is the C/R bit, where 0 is command and 1 is
response.
(as you noted)
The last bit of a DSAP is the I/G bit, where a 0 is individual, and a 1
is
group. Hence DSAP 04 is SNA Path Control Individual, and DSAP 05 is SNA
Path Control Group. (so you need 0d to cover group DSAPs).
I'm guessing that NetBIOS, and IPX (F0 and E0) also use group DSAPs,
hence the
01 01 mask.
HTH, Fred.
Brian Hescock wrote:
>
> We usually see SNA filtered with 0x0000 0x0D0D but...
>
> Based upon all of the examples I've seen on CCO, as shown below, we only
> need to worry about the response for the SSAP (mask 0x0001)
>
> access-list 202 permit 0x0404 0x0001 ! Permits SNA frames (command or
> response)
> access-list 202 permit 0x0004 0x0001 ! Permits SNA Explorers with NULL DSAP
>
> So, given that, isn't 0x0000 0x0C0D technically more correct than 0x0000
> 0x0D0D since we only worry about the response for the SSAP?
>
> Also, if for SNA we only change the SSAP for the response (0x0404
> 0x0001), why do examples for Netbios and IPX use a mask of 0x0101 (as
> in 0xF0F0 0x0101 and 0xE0E0 0x0101)? Every doc I've seen on CCO is
> consistent with regards to difference between SNA and netbios / ipx, any
> idea why the difference in the mask?
>
> Brian
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