In the process of debugging a python irc bot that can't seem to connect, I thought "I know, I'll just tcpdump it and see what it's doing." So I ran tcpdump like I usually do and it says it's captured packets, but doesn't actually write the cap file.
tcpdump -v src host <IP address> and port <port number> >>out.txt 2>>err.txt -w capture.cap
on multiple IP-s while the other parts of the script initiates some traffic in the background.
We want check if packets are coming back to us, and examine manually only those cases when we receive packages.
I'm running a KVM instance inside of OpenStack, and it isn't getting an IP address from the DHCP server.
Using tcpdump, I can see the request and reply packets on vnet0 of the compute host:
# tcpdump -i vnet0 -n port 67 or port 68
tcpdump: WARNING: vnet0: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on vnet0, link-type EN10MB (Ethe