Category Archives: Linux


Replaying PCap to specific network interface

For replaying offline pcap file captured by Wireshark or Windump can be used following tools. On windows was sending throughput lower than on Linux devices, where top speed was done on pcapbulkreplay (300Mbs on lowend 1Gbps network card).



  • tool able to send offline traffic at specific speed (1Mbs, 100Mbs, maximum of interface throughput)
  • To list all available interfaces use –listnics

Example: tcpreplay.exe –listnics

Available network interfaces:
Alias Name Description
%0 \Device\NPF_{DE165B82-8C92-41DD-82DB-0AEF6B8CB7B4}
VMware vmxnet3 virtual network device
%1 \Device\NPF_{99846C37-3FA8-4C69-8DBC-FB80FDA208D2}
VMware vmxnet3 virtual network device

  • to send unmodified traffic to selected NIC use -i %{interface alias}

Example: tcpreplay.exe -t -i %1 c:\Pcaps\taumagic.pcap


sending out \Device\NPF_{99846C37-3FA8-4C69-8DBC-FB80FDA208D2}
processing file: c:\Pcaps\taumagic.pcap
Actual: 1763313 packets (324062931 bytes) sent in 80.99 seconds. Rated: 4001271.0 bps, 30.53 Mbps, 21771.98 pps
Statistics for network device: \Device\NPF_{99846C
Attempted packets: 1763313
Successful packets: 1763313
Failed packets: 0
Retried packets (ENOBUFS): 0
Retried packets (EAGAIN): 0


tcpreplay is much faster than it’s Windows cousin, has same usage


net-snmp configure for SNMPv3 (linux)

Download from

Install openssl-dev to support encryption into net-snmp

run in bash
net-snmp-create-v3-user -a SHA -A “abcd12345″ -x AES -X “abcd12345″ tomaspospisil
snmpwalk -v 3 -On -l authPriv -u tomaspospisil -a SHA -A abcd12345 -x AES -X abcd12345 localhost 1
snmptrap -v 3 -l AuthPriv -a SHA -A “abcd12345″ -x AES -X “abcd12345″ -u tomaspospisil 41 .

How to get localized password key from snmpd configuration:
After you add new user and start snmpd daemon:
locate file /var/net-snmp/snmpd.conf
For every user there is line like:
usmUser 1 3 0x80001f88809907967e3a00ec5000000000 “newuser” “newuser” NULL . 0xcc036e328eaebb3948ef3f20d082a0e1 . 0xcc036e328eaebb3948ef3f20d082a0e1 0x
In this example ‘cc036e328eaebb3948ef3f20d082a0e1′ is password key for Auth and Priv