Brocade Communications Systems 6650 manual Port ID TLV packet format, TTL value

8 General LLDP operating principles

There are several ways in which a port may be identified, as shown in Figure 43. A port ID subtype, included in the TLV, indicates how the port is being referenced in the Port ID field.

TABLE 43	Port ID subtypes
ID subtype	Description
0	Reserved
1	Interface alias
2	Port component
3	MAC address
4	Network address
5	Interface name
6	Agent circuit ID
7	Locally assigned
8 – 255	Reserved

Brocade ICX 6650 devices use port ID subtype 3, the permanent MAC address associated with the port. Other third party devices may use a port ID subtype other than 3. The port ID appears similar to the following on the remote device, and in the CLI display output on the Brocade device (show lldp local-info).

Port ID (MAC address): 748e.f80c.5f40

The LLDPDU format is shown in “LLDPDU packet format” on page 187.

The Port ID TLV format is shown below.

FIGURE 14 Port ID TLV packet format

TLV Type = 3

TLV Information String Length = 2

Time to Live (TTL)

7 bits 9 bits 2 octets

TTL value

The Time to Live (TTL) Value is the length of time the receiving device should maintain the information acquired by LLDP in its MIB.

The TTL value is automatically computed based on the LLDP configuration settings. The TTL value will appear similar to the following on the remote device, and in the CLI display output on the Brocade device (show lldp local-info).

Time to live: 40 seconds

If the TTL field has a value other than zero, the receiving LLDP agent is notified to completely replace all information associated with the LLDP agent/port with the information in the received

LLDPDU.

If the TTL field value is zero, the receiving LLDP agent is notified that all system information associated with the LLDP agent/port is to be deleted. This TLV may be used, for example, to signal that the sending port has initiated a port shutdown procedure.

The LLDPDU format is shown in “LLDPDU packet format” on page 187.

190	Brocade ICX 6650 Administration Guide
	53-1002600-01