MSTP (802.1q or 802.1s) BPDU from Cisco ?

Archived from groups: comp.dcom.sys.cisco,comp.protocols.misc,comp.dcom.lans.ethernet (More info?)

Hi All,
Does any one here know what is Cisco 2950A sending out as MSTP Bpdus?

While CIST information seems to be OK, MST Extension has another &
unknown format.

The version 3 length field in the Cisco BPDU is in the wrong location:
it occupies the same location as the format selector defined in the 802.1s.

It seems, that the 16 bytes configuration digest in the BPDU from Cisco
does not follow the recommendation of the 802.1s. They have different
values compared with those value shown in 802.1s Table 13-2. So Cisco
may not use HMAC-MD5 or the signature key as specified in 802.1s 13-7
(4), and Table 13-1.

"CIST Internal Root Path Cost" and "CIST Bridge identifier" occupy
wrong positions.

"CIST Remaing hops" seems to have 2 bytes instead of 1.

I have not discovered MST Configuarion Messages because of problems
above.

I was discovering CISCO bridge *C3550 Software (C3550-I5Q3L2-M),
Version 12.1(12c)EA1* by Ethereal 0.10.5

Archived from groups: comp.dcom.sys.cisco,comp.protocols.misc,comp.dcom.lans.ethernet (More info?)

Hi All,
It turned out, that my version of Cisco's switch
is too old and these problems are well known and
fixed in more new version. Who has at least 12.1(19)EA1d or
whatever's latest? Can you parse/check outgoing MSTP BPDU?

Thanks a lot, Thom

thomas_finne wrote:

> Hi All,
> Does any one here know what is Cisco 2950A sending out as MSTP Bpdus?
>
> While CIST information seems to be OK, MST Extension has another &
> unknown format.
>
> The version 3 length field in the Cisco BPDU is in the wrong location:
> it occupies the same location as the format selector defined in the 802.1s.
>
> It seems, that the 16 bytes configuration digest in the BPDU from Cisco
> does not follow the recommendation of the 802.1s. They have different
> values compared with those value shown in 802.1s Table 13-2. So Cisco
> may not use HMAC-MD5 or the signature key as specified in 802.1s 13-7
> (4), and Table 13-1.
>
> "CIST Internal Root Path Cost" and "CIST Bridge identifier" occupy
> wrong positions.
>
> "CIST Remaing hops" seems to have 2 bytes instead of 1.
>
> I have not discovered MST Configuarion Messages because of problems
> above.
>
> I was discovering CISCO bridge *C3550 Software (C3550-I5Q3L2-M),
> Version 12.1(12c)EA1* by Ethereal 0.10.5
>
>
>
>
>
>
>
>