H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 218)

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This is the fast sending mechanism of LLDP. With this mechanism, a specific number of LLDPDUs are sent
successively at the 1-second interval to help LLDP neighbors discover the local device as soon as possible.
Then, the normal LLDPDU transit interval resumes.
Receiving LLDPDUs
An LLDP-enabled port operating in TxRx mode or Rx mode checks the TLVs carried in every LLDPDU it
receives for validity violation. If valid, the information is saved and an aging timer is set for it based on
the TTL TLV carried in the LLDPDU. If the TTL TLV is zero, the information is aged out immediately.
Compatibility of LLDP with CDP
You must enable CDP compatibility for your device to work with Cisco IP phones.
As your LLDP-enabled device cannot recognize Cisco Discovery Protocol (CDP) packets, it does not
respond to the requests of Cisco IP phones for the voice VLAN ID configured on the device. This can
cause a requesting Cisco IP phone to send voice traffic untagged to your device, disabling your device
to differentiate voice traffic from other types of traffic.
CDP compatibility enables LLDP on your device to receive and recognize CDP packets from Cisco IP
phones and respond with CDP packets carrying the voice VLAN configuration TLV for the IP phones to
configure the voice VLAN automatically. The voice traffic is confined in the configured voice VLAN to be
differentiated from other types of traffic.
CDP-compatible LLDP operates in one of the follows modes:
• TxRx—CDP packets can be transmitted and received.
• Disable—CDP packets can neither be transmitted nor be received.
Protocols and standards
• IEEE 802.1AB-2005, Station and Media Access Control Connectivity Discovery
• ANSI/TIA-1057, Link Layer Discovery Protocol for Media Endpoint Devices
LLDP configuration guidelines
When you configure LLDP, follow these guidelines:
• To make LLDP take effect, enable it both globally and at port level.
• To advertise LLDP-MED TLVs other than the LLDP-MED capabilities TLV, include the LLDP-MED
capabilities TLV.
• To remove the LLDP-MED capabilities TLV, remove all other LLDP-MED TLVs.
• To remove the MAC/PHY configuration TLV, remove the LLDP-MED capabilities set TLV first.
• When the advertising of LLDP-MED capabilities TLV and MAC/PHY configuration/status TLV is
disabled, if the LLDP-MED capabilities set TLV is included, the MAC/PHY configuration/status TLV
is included automatically.
• When you configure LLDP settings for ports in batch, if you do not set the TLVs, each port uses its
own TLV settings.