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LLDP "Operational MAU type" (802.3 TLV) is zero for GS724Tv3
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I've enabled the optional LLDP TLVs on all my ports.
When I receive the 802.3 organizationally specific TLV subtype 1, the oerational MAU type is zero.
What the operational MAU type should be is 30. The RFC for this is:
dot3MauType1000BaseTFD OBJECT-IDENTITY
STATUS current
DESCRIPTION "Four-pair Category 5 UTP, full duplex mode"
REFERENCE "[IEEE 802.3 Std.], Section 40"
::= { dot3MauType 30 }
When I check on the web interface, it shows 1000mbit, full duplex. The switch can only do 1000-base-t on 4 pair of unshielded twisted pair.
It would be handy to be able to get this information and verify that everything was as it should be.
But the latest firmware (just downloaded it) gives a zero. This is the wrong answer ;-)
Here's what the dump of the TLV shows:
ORG SPECIFIC DUMP: 00120f: DUMP (9 bytes): 00 12 0f 01 03 00 01 00 00
You can read about this in Annex G of the 802.1AB (LLDP) spec. On my copy this spans pages 132 and 133.
An OUI of 00-12-0F means it's the 802.3 TLV (as I expect).
The last two bytes (octets) are the "operational MAU type". As you can see they are both zero.
The only reason for them to be zero is if the type of MAU isn't listed in RFC 3636. But it is.
So, it's an error for it to be zero.
11 Replies
I forgot to say that the "autonegotiation support/status" field (0x03) is correct. 0x01 means that auto-negotiation is supported. 0x02 means that auto-negotiation is enabled. So together they make 0x03. Hurray! That's correct.
The G 2.2 PMD auto-negotiation advertised capability field looks wrong too. The value is 0x0001. So, looking again at RFC 3636 - this looks wrong. 0x0001 means that the only thing it is capable of is 1000 mbit full duplex. This one should have a bunch of bits turned on 10,100,1000 full and half duplex. That's 6 bits. 5 are missing ;-).
Maybe the implementers got confused. What they've done here is given the current speed and duplex, not the ones its capable of.
As you can see below - wireshark agrees with me. I should have used wireshark earlier ;-).
The upper red arrow is for the PMD Auto-Negotiation Advertised Capability. It is 0x0001 as my software printed it, and the meaning is clearly spelled out in wireshark. The switch is claiming it only connect at 1000BASE-T full duplex.
The lower red arrow makes the same complaint that I do -- 0x0000 is unknown or invalid.
I'm trying to use this in the Assimilation Suite - which maps host and network interconnections. Here's an example of how I'd like to use it:
If you look at this, I know the Duplex and MTU of the host-side of connections, but not the switch side. LLDP is supposed to provide this information from the switch side. Then I could validate the best practices here: http://assimilationsystems.com/2015/12/23/three-simple-network-best-practices/ For good measure, the MTU is not provided by this switch. The Maximum Frame Size TLV (Section G.5 in the spec) is not provided. I'd love to have both of these. The NICs are the red ovals. You can see that port eth0 is wired to port g6 on the switch. That is, the host's eth0 is plugged into the switch's g6 port.
It turns out that several of the LLDP-MED frames are also bogus.
Manufacturer: is "0xbc00" - should be "Netgear"
Hardware version is "0 0x0"
Firmware version is "rrr ttt"
Asset is "Asset 1717"
These are all ASCII (or perhaps UTF-8) strings.
They are all maximum length - with blanks filling out the length. The TLVs really ought to be the right length - although that's not a huge problem. Strangely enough, the hardware version string has the extra blanks after the "0" and before the "0x0".
On the plus side, the serial number, model and software version all look good.
I've now verified that three different switches that I own (including an 8-port model) have the same bugs.
I tried to attach a new picture like I did above, but something has changed in the interface, and I can't seem to do that any more.
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