ifconfig -a display flags

Answer

Display Flags

When you issue the ifconfig -a command for an interface you might see any of
the following flags:

ALLMULTI
The interface will receive all multicast packets.

BROADCAST
The interface supports broadcast packets. This is a read-only flag that is set by the driver.

CLUIF
The interface is used for the cluster interconnect.

DEBUG
Driver dependent debugging is enabled.

LOOPBACK
The interface is a loopback mode. Packets transmitted on this interface will be looped back in the driver and not be
transmitted out on the network.

MULTICAST
The interface supports multicast packets. This is a read-only flag that is set by the driver, does not mean that a multicast address is configured for the interface.

MULTINET
Multiple networks are configured on the interface. This means that an IP alias is in a different subnet than the primary IP address.

NOARP
The interface is not using address resolution protocol (ARP). It will neither transmit nor respond to ARP requests.

NOCHECKSUM
The interface does not perform checksums on transmitted or
received packets. Use this only on very reliable network media.

NOTRAILERS
Trailer link-level encapsulation for transmitted packets is
disabled.

OACTIVE
The interface is actively transmitting packets. This is a read-only flag that is set by the driver.

PFCOPYALL
All packets transmitted on this interface are copied and passed to the packet filter program.

POINTOPOINT
The interface is point-to-point link. This is a read-only flag that is set by the driver.

PROMISC
The interface is in promiscuous mode. All packets received are copied and passed to the packet filter program.

PSEG
The interface supports private segments.

QUORUMLOSS
UP interface marked DOWN due to cluster quorum loss.

RUNNING
The driver has allocated resources for the interface, and is
ready to transmit and receive packets. This is a read-only flag that is set by the driver.It is not applicable to loopback devices, for example, lo0.

SIMPLEX
The interface cannot hear its own transmissions. This is a read-only flag that is set by the driver.

UP
The interface is up. This flag is turned on when an address has been configured on the interface.

VAR_MTU
The interface supports variable Maximum Transmission Unit(MTU)sizes. The is a read-only flag that is set by the driver.

Grouprt
The interface supports group routing.