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Output format:

kuznet@alisa:~ $ ip link ls eth0
3: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc cbq qlen 100
    link/ether 00:a0:cc:66:18:78 brd ff:ff:ff:ff:ff:ff
kuznet@alisa:~ $ ip link ls sit0
5: sit0@NONE: <NOARP,UP> mtu 1480 qdisc noqueue
    link/sit brd
kuznet@alisa:~ $ ip link ls dummy
2: dummy: <BROADCAST,NOARP> mtu 1500 qdisc noop
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
kuznet@alisa:~ $

The number before each colon is an interface index or ifindex. This number uniquely identifies the interface. This is followed by the interface name (eth0, sit0 etc.). The interface name is also unique at every given moment. However, the interface may disappear from the list (f.e. when the corresponding driver module is unloaded) and another one with the same name may be created later. Besides that, the administrator may change the name of any device with ip link set name to make it more intelligible.

The interface name may have another name or NONE appended after the @ sign. This means that this device is bound to some other device, i.e. packets send through it are encapsulated and sent via the ``master'' device. If the name is NONE, the master is unknown.

Then we see the interface mtu (``maximal transfer unit''). This determines the maximal size of data which can be sent as a single packet over this interface.

qdisc (``queuing discipline'') shows the queuing algorithm used on the interface. Particularly, noqueue means that this interface does not queue anything and noop means that the interface is in blackhole mode i.e. all packets sent to it are immediately discarded. qlen is the default transmit queue length of the device measured in packets.

The interface flags are summarized in the angle brackets.

1cm NB. There are other flags but they are either obsolete (NOTRAILERS) or not implemented (DEBUG) or specific to some devices (MASTER, AUTOMEDIA and PORTSEL). We do not discuss them here.

The second line contains information on the link layer addresses associated with the device. The first word (ether, sit) defines the interface hardware type. This type determines the format and semantics of the addresses and is logically part of the address. The default format of the station address and the broadcast address (or the peer address for pointopoint links) is a sequence of hexadecimal bytes separated by colons, but some link types may have their natural address format, f.e. addresses of tunnels over IP are printed as dotted-quad IP addresses.

1cm NB. NBMA links have no well-defined broadcast or peer address, however this field may contain useful information, f.e. about the address of broadcast relay or about the address of the ARP server.

1cm NB. Multicast addresses are not shown by this command, see ip maddr ls in Sec.9 (p.[*] of this document).

next up previous contents
Next: Statistics: Up: ip link show Previous: Arguments:   Contents