LLDP DCBX Packet Format Examples IEEE and CEE (wireshark)

Version 4

    This post discusses and shows the format of the Link Layer Discovery Protocol (LLDP) packet with the Data Center Bridging eXchange (DCBX) type-length-values (TLVs) (IEEE and CEE examples).

     

    References

     

    Overview

    There are two formats for LLDP DCBX TLVs:

    • The format specified by the IEEE standard
    • The format specified by the CEE standard

    For more information about the differences, see DCBX Versions and Support on Mellanox  Ethernet Switches.

     

    The examples below are run on the Mellanox Ethernet SN2700 switch.

     

     

    LLDP DCBX - IEEE Mode

     

    1. Enable LLDP.

    switch (config) # lldp

    2. In the interface configuration mode, enable the DCBX TLV, for example:

    switch (config) # interface ethernet 1/1 lldp tlv-select management-address dcbx

     

    Note: You can enable any combination of TLVs. By default, all TLVs are enabled, including the DCBX IEEE TLVs.

     

    3. Enable Priority Flow Control (PFC) specifying the priority for that interface, for example, enable PFC on priority 4 on interface ethernet 1/1.

     

    See also:

     

    4. Run wireshark on the server connected to that switch, and capture the LLDP packets (see also attached).

    Verify that PFC is enabled on priority 4, via the DCBX-IEEE LLDP TLV.

     

    Note: When enabling DCBX TLVs (using the IEEE format), the switch will send four TLVs as defined in the standard, see DCBX Versions and Support on Mellanox  Ethernet Switches.

    • ETS Configuration
    • ETS Recommendation
    • PFC
    • Application Priority

     

    Note: In the example the IEEE format uses four different TLVs: ETS configuration, ETS Recommendation, PFC, and Application priority.

     

    dcbx.PNG

     

     

    LLDP DCBX - CEE Mode

     

    1. Enable LLDP.

    switch (config) # lldp

     

    2. In the interface configuration mode, enable the DCBX TLV, for example:

    switch (config) # interface ethernet 1/1 lldp tlv-select management-address dcbx-cee

     

    Note: You can enable any combination of TLVs. By default all TLVs are enabled, except the DCBX CEE. The DCBX CEE TLV should be explicitly configured.

     

    3. Enable PFC and specify priority for that interface, for example, enable PFC on priority 4 on interface ethernet 1/1.

     

    See also:

     

    4. Run wireshark on the server connected to that switch, and capture the LLDP packets (see also attached).

    Verify that PFC is enabled on priority 4, via DCBX-CEE LLDP TLV.

     

    Note: The CEE format uses one TLV frame for PFC and Application priority, and does not include ETS. See attached.

     

    lldp-cee.PNG

     

     

    Enable All TLVs

    When enabling all TLVs, which is the default configuration on Mellanox Ethernet switches, the DCBX IEEE TLVs will be sent, but the DCBX CEE TLV will not be sent.

     

    switch (config) # interface ethernet 1/1 lldp tlv-select all

     

    See below, and also the attached pcap file.

     

    dcbx2.PNG