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3com S7906E Instruccion De Instalación

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1-6 
z 
TxRx mode. A port in this mode sends and receives LLDP frames. 
z 
Tx mode. A port in this mode only sends LLDP frames.  
z 
Rx mode. A port in this mode only receives LLDP frames. 
z 
Disable mode. A port in this mode does not send or receive LLDP frames. 
Each time the LLDP operating mode of a port changes, its LLDP protocol state machine re-initializes. To 
prevent LLDP from being initialized too frequently at times of frequent operating mode change, an 
initialization delay, which is user configurable, is introduced. With this delay mechanism, a port must 
wait for the specified interval before it can initialize LLDP after the LLDP operating mode changes.  
How LLDP Works 
Transmitting LLDP frames 
An LLDP-enabled port operating in TxRx mode or Tx mode sends LLDP frames to its directly connected 
devices both periodically and when the local configuration changes. To prevent the network from being 
overwhelmed by LLDP frames at times of frequent local device information change, an interval is 
introduced between two successive LLDP frames.  
This interval is shortened to 1 second in either of the following two cases:  
z 
A new neighbor is discovered, that is, a new LLDP frame is received carrying device information 
new to the local device.  
z 
The LLDP operating mode of the port changes from Disable/Rx to TxRx or Tx.  
This is the fast sending mechanism of LLDP. With this mechanism, a specific number of LLDP frames 
are sent successively at the 1-second interval to help LLDP neighbors discover the local device as soon 
as possible. Then, the normal LLDP frame transmit interval resumes.  
Receiving LLDP frames 
An LLDP-enabled port operating in TxRx mode or Rx mode checks the TLVs carried in every LLDP 
frame it receives for validity violation. If valid, the information is saved and an aging timer is set for it 
based on the time to live (TTL) TLV carried in the LLDPDU. If the TTL TLV is zero, the information is 
aged out immediately.  
Protocols and Standards 
The protocols and standards related to LLDP include: 
z 
IEEE 802.1AB-2005, Station and Media Access Control Connectivity Discovery 
z 
ANSI/TIA-1057, Link Layer Discovery Protocol for Media Endpoint Devices 
LLDP Configuration Task List 
Complete these tasks to configure LLDP: 
Task 
Remarks 
Required 
Optional 
Optional 
Optional 
Optional