ASTERISK SIP / UDP Checksum Error

Hello together

i found something strange. If I am creating an tcpdump every Packet sent from the asterisk server have an Bad Checksum. Rdp can be turned off in the config file but how can I turn off in the sip protokoll.
If this error occures I have problems on the isdn / S2M side.
I am using Digium Card Single PRI with echo canceller.


This is typically an artifact of the packet capture program that you are using. If the checksums are really invalid it is a hardware or OS kernel problem.


thats wrong. Asterisk 1.4.XX don’t create this errors.
How can I get the card correctly working ? And Asterisk 1.2.XX without this errors ?


In that case, identify the socket option that allows the sending of bad checksums, search the code for it, and revert it to the value in the previous version. I doubt you will find it.

Checksums are not calculated by UDP applications, they are calculated by the kernel.


so all outher services have right checksum only from the asterisk service are wrong.
So I’m wondering because many people have that issues …
The machine was also changed ( Hardware and OS ) but the same result …



can the checksum be turned off in an config file for sip packages ?


That wouldn’t make sense as a normal network stack would ignore the resulting packets, when it received them.


set the tos and qos bits to a lower value, if asterisk is running as asterisk as it should then in centos and maybe other distros then it cant set the qos bits to what the default in the sip.conf is, Im not saying this is the problem but it might be, I have seen what you described on both 1.2 and 1.4 from memory we just disabled checksums as it was a known issue with that nic