tcpdump socketcan confusion

I am trying to debug some network issues on a BBB re traffic between the BBB and a web server. This BBB has is also using a canbus with the socketcan interface. I don’t have experience with these tools, but I thought wireshark might help, and that I could use tcpdump on the BBB to feed it.

When I try to run tcpdump, with or without explicitly specifying ether[0], it complains that can0 does not have an IPv4 address assigned, and that CAN link-layer filtering is not implemented, and exits. When I run “tcpdump -D”, it shows only can0, as if eth0 does not exist at all. ifconfig does show eth0, and eth0 and can0 both work, I’m just trying to get more insight into the details of the traffic on eth0.

Can anyone tell my how to persuade tcpdump to ignore can0 and listen to eth0?

tcpdump 4.5.1
libpcap 1.5.3
Linux kernel 3.8.13


tcdump -i eth0