Lost UDP fragments

sluge

New Member
On my PC I have an issue related to UDP: when snmp bulk request comes and response size is larger than MTU (1500), UDP packet fragmented but only the first part is sent to network. I get a traffic dump on the PC and see the only the first fragment is transmitted. It looks like other parts of UDP packet is dropped by network stack/kernel. OS is Linux. Both hosts are in the same subnet.

What can be wrong? Network settings, kernel settings, user space, etc?
 


JulienCC

Member
Hello,

What can be wrong? Network settings, kernel settings, user space, etc?
It could be anything since we dont have a lot of context on your system/kernel/application.
Do you have any iptables rules set on your machines ? Fragmented packets (except the first fragment) wont contain informations such as port and might be filtered by your iptables.

You can set rules with the -f option to target fragmented packets.
 

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