---
name: "mckey"
section: "1"
platform: "linux"
package: "rdma-core"
version: "65.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/mckey"
---

# mckey(1)

RDMA CM multicast setup and simple data transfer test.

## NAME

mckey - RDMA CM multicast setup and simple data transfer test.

## SYNOPSIS

```
mckey -m multicast_address [-s] [-b bind_address] [-c connections]
		[-C message_count] [-S message_size] [-p port_space]
mckey -m multicast_address -s [-b bind_address] [-c connections]
		[-C message_count] [-S message_size] [-p port_space]
mckey -M unmapped_multicast_address -b bind_address [-s] [-c connections]
		[-C message_count] [-S message_size] [-p port_space]
```

## DESCRIPTION

Establishes a set of RDMA multicast communication paths between nodes using the librdmacm, optionally transfers datagrams to receiving nodes, then tears down the communication.

## OPTIONS

- \-m multicast\_address

  IP multicast address to join.

- \-M unmapped\_multicast\_address

  RDMA transport specific multicast address to join.

- \-s

  Send datagrams to the multicast group.

- \-b bind\_address

  The local network address to bind to.

- \-c connections

  The number of QPs to join the multicast group.  (default 1)

- \-C message\_count

  The number of messages to transfer over each connection.  (default 10)

- \-S message\_size

  The size of each message transferred, in bytes.  This value must be smaller than the MTU of the underlying RDMA transport, or an error will occur. (default 100)

- \-o

  Join the multicast group as a send-only full-member. Otherwise the group is joined as a full-member.

-

  - \-l

  Prevent multicast message loopback. Other receivers on the local system will not receive the multicast messages. Otherwise all multicast messages are also send to the host they originated from and local listeners (and probably the sending process itself) will receive the messages. -p port\_space The port space of the datagram communication.  May be either the RDMA UDP (0x0111) or IPoIB (0x0002) port space.  (default RDMA\_PS\_UDP)

## NOTES

Basic usage is to start mckey -m multicast\_address on a server system, then run mckey -m multicast\_address -s on a client system.

Unique Infiniband SA assigned multicast GIDs can be retrieved by invoking mckey with a zero MGID or IP address.  (Example, -M 0 or -m 0.0.0.0).  The assigned address will be displayed to allow mckey clients to join the created group.

Because this test maps RDMA resources to userspace, users must ensure that they have available system resources and permissions.  See the libibverbs README file for additional details.

## SEE ALSO

[rdma\_cm(7)](/rdma_cm/7.md), [ucmatose(1)](/ucmatose/1.md), [udaddy(1)](/udaddy/1.md), [rping(1)](/rping/1.md)