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Why would wireshark on one PC capture LLDP packets and another not?

asked 2024-04-15 19:02:33 +0000

SeeCwriter gravatar image

I have a device that's transmitting Link Layer Discovery Protocol (LLDP) packets. I have two Windows PCs running Win10 Enterprise, ver 22H2, build 19045. The device and the PCs are all on the same sub-net, on their own layer 2 Netgear switches. Both PC's are running v4.2.0 of wireshark. I add filter eth.type==0x88cc to wireshark on both PCs. One PC captures the device's LLDP packets, the other does not. What could be the issue?

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Typical troubleshooting would be to swap PC's and see if the issue stivks to the PC or to the switch.

hugo.vanderkooij gravatar imagehugo.vanderkooij ( 2024-04-16 06:00:38 +0000 )edit

Also Wireshark profiles may be different on the two instances.

grahamb gravatar imagegrahamb ( 2024-04-16 08:04:57 +0000 )edit

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answered 2024-04-16 14:07:40 +0000

SeeCwriter gravatar image

It turns out that LLDP broadcast packets are treated differently than normal broadcast packets. Normally a broadcast goes to all devices on the same sub-net. With LLDP, the packets are only forwarded to devices on the same network switch as the device sending the LLDP packets.

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Perhaps a switch in the network recognizes the lldp packet and so does not forward it.

7ACE gravatar image7ACE ( 2024-04-16 14:48:35 +0000 )edit

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Asked: 2024-04-15 19:02:33 +0000

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Last updated: Apr 16