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Wireshark-bugs: [Wireshark-bugs] [Bug 12885] New: VTPv3 dissection

Date: Mon, 12 Sep 2016 12:12:08 +0000
Bug ID 12885
Summary VTPv3 dissection
Product Wireshark
Version Git
Hardware All
OS All
Status UNCONFIRMED
Severity Normal
Priority Low
Component Dissection engine (libwireshark)
Assignee [email protected]
Reporter [email protected]

Created attachment 14910 [details]
VTPv3 advertisements

Build Information:
Version 2.3.0 (v2.3.0rc0-514-gaa2471d from unknown)
--
Dear Wireshark developers,

It seems that VTPv3 packet format is not backward compatible with VTPv1/2. I
attached samples of summary Advertisement with subset information and summary
advertisement w/o subset info. Below is interpreted information reported by
IOS:

Feature VLAN:
--------------
VTP Operating Mode                : Server
Number of existing VLANs          : 5
Number of existing extended VLANs : 0
Maximum VLANs supported locally   : 4096
Configuration Revision            : 10
Primary ID                        : aabb.cc80.0200
Primary Description               : SW01234567890123457890
MD5 digest                        : 0x95 0x76 0xEE 0x60 0x0D 0xA3 0x91 0x33 
                                    0xF2 0x16 0x20 0x9D 0x5A 0x4F 0xB3 0x03

I see that Primary ID is located at 0x42 offset and is 6 bytes length. The MD5
digest is at 0x62 (16 bytes). The configured hostname for the primary server is
SW0123456789012345678901234567890123456789, but VTP process shrinked it to
SW01234567890123457890 (primary description), it is located at 0x48, but I'm
not sure about exact length. Only standard VLANs are in the attached
advertisements (1,1002-1005). The byte 0x75 is surely part of revision id. The
offset values are related to whole packet, not to the VTP packet.

Kind Regards,
Garri


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