How to send captured packets to a different destination?

You'll need to use a tool that's capable of replaying pcap files. No special trick to it. An example would tcpreplay. A simple search for "replay pcap file" will turn up even more tools gloriously up to date within the very second that you hit enter in your search engine of choice.

I wanted to capture some SNMP traps and keep them to test my application later. So I don't want to generate traps each time I wanted to test my application. I would like to post how I have done this. Hope this may help someone.

1) Capturing one packet with destination host 192.168.159.149 and port 1620 and saving it to a file

tcpdump -n -c 1 -s 0 dst host 192.168.159.149 and port 1620 -w snmp.pcap -i eth0

2) Reading captured packet

tcpdump -r snmp.pcap -X

3) Changing destination ip, MAC and checksum

tcprewrite --infile=snmp.pcap --outfile=snmp2.pcap --dstipmap=192.168.159.149:192.168.159.150 --enet-dmac=00:0c:29:d6:0f:61 --fixcsum

4) Replaying

tcpreplay --intf1=eth0 snmp2.pcap