If configured with --enable-debug, then you can specify a verbosity level for debugging output. Higher numbers increase verbosity.

Print nothing except the statistics at the end of the run

Allows you to select the packet timing method to use:

nano

select

ioport

gtod [default]

Set a limit for the maximum number of milliseconds that tcpreplay will sleep between packets. Effectively prevents long delays between packets without effecting the majority of packets. Default is disabled.

When enabling verbose mode (-v) you may also specify one or more additional arguments to pass to tcpdump to modify the way packets are decoded. By default, -n and -l are used. Be sure to quote the arguments like: -A "-axxx" so that they are not interpreted by tcpreplay. Please see the tcpdump(1) man page for a complete list of options.

This option loads the specified pcap(s) into RAM before starting to send in order to improve replay performance while introducing a startup performance hit. Preloading can be used with or without --loop. This option also suppresses flow statistics collection for every iteration, which can significantly reduce memory usage. Flow statistics are predicted based on options supplied and statistics collected from the first loop iteration.

If you have a pcap file you would like to use to send bi-directional traffic through a device (firewall, router, IDS, etc) then using tcpprep you can create a cachefile which tcpreplay will use to split the traffic across two network interfaces.

If you captured network traffic using a network tap, then you can end up with two pcap files- one for each direction. This option will replay these two files at the same time, one on each interface and inter-mix them using the timestamps in each.

Required network interface used to send either all traffic or traffic which is marked as 'primary' via tcpprep. Primary traffic is usually client-to-server or inbound (RX) on khial virtual interfaces.

Optional network interface used to send traffic which is marked as 'secondary' via tcpprep. Secondary traffic is usually server-to-client or outbound (TX) on khial virtual interfaces. Generally, it only makes sense to use this option with --cachefile.

Optional pcap file name used to receive traffic.

Override default of processing all packets stored in the capture file and only send packets that are part of a supplied list of packet numbers.

-x P:1-5,9,15,72-

would skip packets 1 through 5, the 9th and 15th packet, and packets 72 until the end of the file

Override default of processing all packets stored in the capture file and only send packets that are NOT part of a supplied list of packet numbers.

-x P:1-5,9,15,72-

would skip packets 1 through 5, the 9th and 15th packet, and packets 72 until the end of the file

By default, tcpreplay will use loop delay with microsecond accuracy (loopdelay-ms). In order to use loop delay with nanosecond accuracy you need to use nano packet timing mode.

By default, tcpreplay will send packets based on the size of the "snaplen" stored in the pcap file which is usually the correct thing to do. However, occasionally, tools will store more bytes then told to. By specifying this option, tcpreplay will ignore the snaplen field and instead try to send packets based on the original packet length. Bad things may happen if you specify this option.

By default, tcpreplay will send all the packets. Alternatively, you can specify a maximum number of packets to send.

By default, tcpreplay will send all the packets. Alternatively, you can specify a maximum number of seconds to transmit.

Specify a value to modify the packet replay speed. Examples:

    2.0 will replay traffic at twice the speed captured


    0.7 will replay traffic at 70% the speed captured

Specify a value to regulate the packet replay to a specific packet-per-second rate. Examples:

    200 will replay traffic at 200 packets per second


    0.25 will replay traffic at 15 packets per minute

Specify a floating point value for the Mbps rate that tcpreplay should send packets at.

Allows you to step through one or more packets at a time.

When trying to send packets at very high rates, the time between each packet can be so short that it is impossible to accurately sleep for the required period of time. This option allows you to send multiple packets at a time, thus allowing for longer sleep times which can be more accurately implemented.

Set to a percentage between 0 and 100 to simulate packet loss at send. Loss is random: each packet is independently dropped with the given probability, not on a fixed pattern (e.g. not every Nth packet), so the actual number dropped will vary slightly run to run. Dropped packets are not sent and are not counted as failed.

Examples:

    25 will drop approximately one quarter of packets, chosen at random


    100 will drop every packet (nothing will be sent)

Ensure IPv4 and IPv6 packets will be unique for each --loop iteration. This is done in a way that will not alter packet CRC, and therefore will generally not affect performance. This option will significantly increase the flows/sec over generated over multiple loop iterations.

Number of --loop iterations before a new unique IP is assigned. Default is 1. Assumes both --loop and --unique-ip.

This feature will detect netmap capable network drivers on Linux and BSD systems. If detected, the network driver is bypassed for the execution duration, and network buffers will be written to directly. This will allow you to achieve full line rates on commodity network adapters, similar to rates achieved by commercial network traffic generators. Note that bypassing the network driver will disrupt other applications connected through the test interface. See INSTALL for more information.

This feature can also be enabled by specifying an interface as 'netmap:<intf>' or 'vale:<intf>. For example 'netmap:eth0' specifies netmap over interface eth0.

Number of seconds to delay after netmap is loaded. Required to ensure interfaces are fully up before netmap transmit. Requires netmap option. Default is 10 seconds.

Suppress the collection and printing of flow statistics. This option may improve performance when not using --preload-pcap option, otherwise its only function is to suppress printing.

The flow feature will track and print statistics of the flows being sent. A flow is loosely defined as a unique combination of a 5-tuple, i.e. source IP, destination IP, source port, destination port and protocol.

If --loop is specified, the flows from one iteration to the next will not be unique, unless the packets are altered. Use --unique-ip or tcpreplay-edit to alter packets between iterations.

This option will track and report flow expirations based on the flow idle times. The timestamps within the pcap file are used to determine the expiry, not the actual timestamp of the packets are replayed. For example, a value of 30 suggests that if no traffic is seen on a flow for 30 seconds, any subsequent traffic would be considered a new flow, and thereby will increment the flows and flows per second (fps) statistics.

This option can be used to optimize flow timeout settings for flow products. Setting the timeout low may lead to flows being dropped when in fact the flow is simply slow to respond. Configuring your flow timeouts too high may increase resources required by your flow product.

Note that using this option while replaying at higher than original speeds can lead to inflated flows and fps counts.

Default is 0 (no expiry) and a typical value is 30-120 seconds.

Note that timed delays are a "best effort" and long delays between sending packets may cause equally long delays between printing statistics.

This feature will detect AF_XDP capable network drivers on Linux systems that have 'libxdp-dev' and 'libbpf-dev' installed. If detected, the network stack is bypassed and packets are sent directly to an eBPF enabled driver directly. This will allow you to achieve full line rates on commodity network adapters, similar to rates achieved by commercial network traffic generators.

An AF_XDP socket is bound to a single hardware queue. Queue 0 is used by default; on a multi-queue adapter you may need a different one, since the queue must exist on the adapter and traffic steering may not use queue 0. If the queue does not exist the socket cannot be created.

By default, if an AF_XDP socket cannot be set up on the interface - the driver has no XDP support at all, or the requested queue does not exist - tcpreplay warns and replays using its default injection method instead of failing. Use this to make that case a hard error, which is what you want when benchmarking: a silent change of injection method would change what is being measured.

This feature is available on Linux systems with a kernel that supports io_uring and 'liburing-dev' installed. Packets are still sent through a PF_PACKET raw socket, but sends are submitted asynchronously through an io_uring submission queue, which reduces per-packet syscall overhead and lets the kernel process transmissions while tcpreplay prepares the next packet.

By default, tcpreplay injects packets with PF_PACKET, which writes directly to the network driver below the IP stack. This means locally-generated netfilter/iptables rules (and anything else hooked into the normal Linux IP stack) never see the traffic, even when replaying it on the same host that has those rules configured.

This option instead sends each packet’s IP header and payload through a PF_INET raw IP (SOCK_RAW) socket bound to the interface given by --intf1/--intf2, so the kernel’s normal IP stack — including netfilter/iptables — processes it like any other locally-generated packet.

The trade-off is L2 fidelity: the kernel builds its own Ethernet framing for the outgoing packet, so the source/destination MAC addresses from the capture are not reproduced, and only IPv4 packets are currently supported. This option is Linux-only and requires appropriate privileges to open a raw socket (typically root or CAP_NET_RAW).