From: Scott Morris (swm@emanon.com)
Date: Sun Aug 22 2004 - 18:02:55 GMT-3
I had seen that referenced before (only once), but couldn't liken the logic
to the 00 (individual?) which is used for explorers. Explorers (and other
things) by definition go to many to be processed.
So I had written that off. Perhaps inaccurately. If there are any
real-life SNA experts hanging around, perhaps we can get a better answer for
it!
From documents that I have seen though, that's not the case. But I'm all
for finding out the truth of things are different!!!
Scott
-----Original Message-----
From: Carlos G Mendioroz [mailto:tron@huapi.ba.ar]
Sent: Sunday, August 22, 2004 3:55 PM
To: Scott Morris
Cc: k_kaloianov@eircom.net; ccielab@groupstudy.com
Subject: Re: NetBIOS and SNA
Scott,
I've seen this a number of times, but I have a doubt regarding it:
The lower bit in SSAP is C/R, meaning command or response.
But on DSAP, the lower bit is I/G, meaning individual/group.
So a destination of group can be there with a 1.
Or am I confused ?
Scott Morris wrote:
> Response SAPs are only in the source part, never will exist in
destination.
> :)
>
> So technically, your mask would be 0x0001. However, being that the
> docCD is a defensible position, on the lab do whatever they do.
>
> Following that logic, if you have no commands, you can't possibly have
> a response, so your exact match mask would work perfectly fine as
> well. With DLSW, you can also use the icannotreach commands to say
unavailable.
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> CISSP, JNCIP, et al.
> IPExpert CCIE Program Manager
> IPExpert Sr. Technical Instructor
> swm@emanon.com/smorris@ipexpert.net
> http://www.ipexpert.net
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of k_kaloianov@eircom.net
> Sent: Sunday, August 22, 2004 11:13 AM
> To: ccielab@groupstudy.com
> Subject: Re: NetBIOS and SNA
>
> Hi Georg,
>
> I was wondering the same thing myself but what I found out recently is
that:
> When using access-lists for you have to consider that a SAP could be
> either command or response, which is appointed by a C/R bit in the
> SSAP, 0 for commands and 1 for responses, and this will be SSAP 0x5
> will be response to SAP 0x4, which all are included in 0x0d0d. If you
> want to block everytning in NETBIOS 0xF1 and 0xF0, your wildcard mask
> will be 0x0101, and on the other hand if you want to block just 0xF0F0
> then you could use wildcard of 0x0000. This is how I'm trying to explain
it to myself, hope it makes sense?
>
>
> Reg,
> Kaloyan
>
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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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