Problem - Bad Checksum
%OSPF-4-ERRRCV: Received invalid packet: Bad Checksum from xxx.xxx.xxx.xxx, interface number
The router generating this message has received an invalid OSPF packet on an interface from neighbor xxx.xxx.xxx.xxx. The packet is invalid because the OSPF checksum is incorrect. The cause of the bad checksum is difficult to define. Some possible causes of the problem are:
A device between the neighbors, such as a switch, is corrupting the packet.
The sending router's packet is invalid. In this case, either the sending router's interface is bad, or the error is caused by a software bug.
The receiving router is calculating the wrong checksum. In this case, either the receiving router's interface is bad, or the error is caused by a software bug. This is the least likely cause of this error message.
Solution
This problem can be difficult to troubleshoot, but you can start with this solution. Cisco has found that this solution is effective in 90 percent of cases. It is important to complete these steps in order:
Change the cable between the routers. In the previous example, this would be the router that sends the bad packet (xxx.xxx.xxx.xxx) and the router that complains about these bad packets.
If the previous step does not fix the problem, use a different port on the switch in between the routers.
If the previous step does not fix the problem, connect the routers directly using a crossover cable (whenever physical location allows). If you receive no further messages, the switch is most likely corrupting the packet.
If this doesn't work, go here:
http://www.cisco.com/en/US/customer/tech/tk365/technologies_tech_note09186a0080094819.shtml
