How the switch passthroughs LLDP packets.

A---B---C

Device B transmits LLDP messages sent by A and C, enabling A and C to establish a neighbor relationship.

For the Device A and Device C are the network nodes which can modify the configuration of LLDP.

Such as:

2015（1/0/1）-----（1/0/1）2011(1/0/31)-------(1/3/1)2023

Configuration for 2015

[2015-125x-af-Ten-GigabitEthernet1/0/1]

#

interface Ten-GigabitEthernet1/0/1

port link-mode bridge

lldp agent nearest-customer admin-status txrx

#

return

[2015-125x-af-Ten-GigabitEthernet1/0/1]%Mar 31 15:17:44:707 2021 2015-125x-af LOCALSVR/6/LOCALSVR_PROMPTED_CHANGE_PWD: -MDC=1;  Please change the password of device management user admin, because the current password is a weak-password.

%Mar 31 15:17:44:839 2021 2015-125x-af SHELL/5/SHELL_LOGIN: -MDC=1; admin logged in from 192.168.89.252.

%Mar 31 15:18:09:335 2021 2015-125x-af LLDP/6/LLDP_CREATE_NEIGHBOR: -MDC=1-Slot=1; Nearest customer agent neighbor created on port Ten-GigabitEthernet1/0/1 (IfIndex 242), neighbor"s chassis ID is 4077-a9f0-38cc, port ID is Ten-GigabitEthernet1/3/1.

[2015-125x-af-Ten-GigabitEthernet1/0/1]

[2015-125x-af-Ten-GigabitEthernet1/0/1]dis lldp neighbor-information list

Chassis ID : * -- -- Nearest nontpmr bridge neighbor

             # -- -- Nearest customer bridge neighbor

             Default -- -- Nearest bridge neighbor

Local Interface Chassis ID      Port ID                    System Name         

XGE1/0/1        9ce8-9572-8326  Ten-GigabitEthernet1/0/1   2011-S6800-H1

XGE1/0/1        4077-a9f0-38cc# Ten-GigabitEthernet1/3/1   6820-2023

XGE1/0/9        74ea-c830-5000  Ten-GigabitEthernet3/0/9   2012-S12504X-AF

XGE1/0/11       74ea-c830-5000  Ten-GigabitEthernet3/0/11  2012-S12504X-AF

XGE1/0/16       9ce8-9574-24ec  Ten-GigabitEthernet1/0/45  2084-S6800-H3

XGE1/0/19       f474-88dd-ddf6  Ten-GigabitEthernet1/0/1   2091-S6860

MGE0/0/3        c4ca-d9b9-bb86  GigabitEthernet2/0/38      S5800-56C

[2015-125x-af-Ten-GigabitEthernet1/0/1]

Configuration for 2011

[2011-S6800-H1]dis cu | include lldp

lldp mode service-bridge

[2011-S6800-H1]dis lldp neighbor-information list

Chassis ID : * -- -- Nearest nontpmr bridge neighbor

             # -- -- Nearest customer bridge neighbor

             Default -- -- Nearest bridge neighbor

Local Interface Chassis ID      Port ID                    System Name          

XGE1/0/1        74ea-c830-5a00  Ten-GigabitEthernet1/0/1   2015-125x-af

XGE1/0/15       9ce8-9572-a12a  Ten-GigabitEthernet3/0/15  2064-S6800-H1

XGE1/0/31       4077-a9f0-38cc  Ten-GigabitEthernet1/3/1   6820-2023

MGE0/0/0        c4ca-d9b9-bb86  GigabitEthernet2/0/16      S5800-56C

[2011-S6800-H1]

[2011-S6800-H1]dis cu | include lldp

lldp mode service-bridge

lldp global enable

return

Configuration for 2023:

[6820-2023]

#

interface Ten-GigabitEthernet1/3/1

port link-mode bridge

lldp agent nearest-customer admin-status txrx

#

[6820-2023-Ten-GigabitEthernet1/3/1]qu

[6820-2023]dis lldp n

[6820-2023]dis lldp neighbor-information l

[6820-2023]dis lldp neighbor-information list

Chassis ID : * -- -- Nearest nontpmr bridge neighbor

             # -- -- Nearest customer bridge neighbor

             Default -- -- Nearest bridge neighbor

LocalIf         Nbr chassis ID  Nbr port ID                     Nbr system name

XGE1/1/23       4077-a9f0-3a34  Ten-GigabitEthernet2/1/24       6820-2035

FGE1/1/25       80e4-55f1-68f0  HundredGigE1/0/29               2031-S6850

XGE1/3/1        9ce8-9572-8326  Ten-GigabitEthernet1/0/31       2011-S6800-H1

XGE1/3/1        74ea-c830-5a00# Ten-GigabitEthernet1/0/1        2015-125x-af

XGE1/3/2        9ce8-9572-a12a  Ten-GigabitEthernet3/0/32       2064-S6800-H1

FGE1/3/25       4077-a9f0-3a34  FortyGigE2/1/25                 6820-2035

MGE0/0/0        c4ca-d9b9-bb86  GigabitEthernet2/0/12           S5800-56C

[6820-2023]

For the Device A and Device C are the network nodes which can"t modify the configuration of LLDP.

Such as:

host A -------Switch B--------host C

For passing the LLDP, one can undo the lldp globally, and then set the ‘l2protocol lldp tunnel dot1q’ on the interface which need pass the lldp.

On the Switch A and C. 

#

lldp agent nearest-customer admin-status txrx

#

On the switch B.

#

lldp mode service-bridge

#

On the switch between the host.

#

undo lldp global enable

#

l2protocol lldp tunnel dot1q

#