From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Sun Aug 22 2004 - 16:55:01 GMT-3
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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