Wireshark-bugs: [Wireshark-bugs] [Bug 1455] LLDPDU MAC-PHY TLV PMD Auto-Neg field is being analy
http://bugs.wireshark.org/bugzilla/show_bug.cgi?id=1455
------- Comment #4 from jyoung@xxxxxxx 2007-04-10 04:15 GMT -------
Hello John,
You wouldn't by some chance be looking at LLDPDU generated by an Avaya IP
phone?
I've attached a small trace that includes two LLDPDUs, one from an Extreme
Summit S300-24 switch the other from it's peer an Avaya 4621SW IP phone.
I had a 10base-T hub between the switch and phone which explains why the two
devices are only communicating with each other at 10-half.
The pmd auto-negotiation advertised capability bits from the Extreme LLDPDU
switch parses as expected, but for the Avaya phone the bits appears to be
inverted. The trace shows the short for the Avaya's pmd auto-negotiation
advertised capability as 0x0536. I suspect that Avaya is generating this value
incorrectly. If I invert the bits of this short from 0x0536 to x6CA0 then the
parsed value makes more sense.
Assuming 0x6ca0:
0110 1100 1010 0000
xx xx x x
42 84 8 2
0x4000 /* b10baseT(1), -- 10BASE-T half duplex mode */
0x2000 /* b10baseTFD(2), -- 10BASE-T full duplex mode */
0x0800 /* b100baseTX(4), -- 100BASE-TX half duplex mode */
0x0400 /* b100baseTXFD(5), -- 100BASE-TX full duplex mode */
0x0080 /* bFdxPause(8), -- PAUSE for full-duplex links */
0x0020 /* bFdxSPause(10), -- Symmetric PAUSE for full-duplex links */
Of course Extreme could have it wrong. I submitted this particular piece of
code to packet-lldp.c. At the time the only LLDPDUs I had were generated by
Extreme switches (both XOS and Extremeware based devices). But the code seemed
pretty straight forward to me so my guess is that your LLDPDU and my Avaya
LLDPDU are generated incorrectly.
I'll be checking with the Avaya tomorrow.
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