tcpdump f5

Amit,

-e shows layer2 info (mac addresses etc.)

-i is interface (tcpdump -i 0.0)

-nnn means don't resolve hostnames or ports (makes tcpdump quicker)

Hope this helps,

N

thanks for help nathan , whats difference between -nnn and -nni

i gave below command without -i it worked , i expected it should ask for -i if i am specifying interface eth0 ?

tcpdump -e -s0 -nni eth0 host 1.1.1.1

Nothing, you can use -nnni or -nnn -i as far as I understand.

i gave below command without -i it worked , i expected it should ask for -i if i am specifying interface eth0 ?

tcpdump -e -s0 -nni eth0 host 1.1.1.1

From running "man tcpdump":

...

-s Snarf snaplen bytes of data from each packet rather than the default of 68 (with SunOS’s NIT, the minimum is actually 96). 68 bytes is adequate for IP, ICMP, TCP and UDP but may truncate protocol information from name server and NFS packets (see below). Packets truncated because of a limited snapshot are indicated in the output with ‘‘[|proto]’’, where proto is the name of the protocol level at which the truncation has occurred. Note that taking larger snapshots both increases the amount of time it takes to process packets and, effectively, decreases the amount of packet buffering. This may cause packets to be lost. You should limit snaplen to the smallest number that will capture the protocol information you’re interested in. Setting snaplen to 0 means use the required length to catch whole packets.