title: Linux: State of Network Interfaces
agents: linux
catalog: os/networking
license: GPLv2
distribution: check_mk
description:
 This check monitors the operational status, link speed, traffic, packet
 counts, discards and errors of network interfaces of a Linux host using
 data sent by the Checkmk agent.

 Please note that the agent only sends information about the current link speed
 setting and link status if {ethtool} is installed and supported by the NIC.

 Depending on the check parameters, this check can go WARN or CRIT when the
 port status changes (i.e. is down), when the link speed changes (e.g. a
 port expected to be set to 1 GBit/s operates only at 100 MBit/s), when the
 absolute or procentual traffic of a port exceeds certain levels or if the
 rate of errors or discards exceeds configurable limits.

 This check supports averaging the in- and outgoing traffic over a configurable
 time range by using an exponentially weighted moving average - just as Linux
 does for the CPU load averages. The averaging can be configured on a per-host
 and per-interface base. Interfaces with averaging turned on yield two additional
 performance values: the averaged in- and outgoing traffic in bytes. If you have
 configured traffic levels, then those levels are applied to the averaged values.

item:
 There are three allowed ways to specify an interface: its index, which simply
 enumerates the interfaces starting from 1, its description and its alias. For this
 check, the description and the alias are the same.

discovery:
 One service is created for each interface that fulfills configurable conditions
 (rule "Network interface and switch port discovery").
 By default, these are interfaces which are currently found {up} and are of type 6, 32,
 62, 117, 127, 128, 129, 180, 181, 182, 205 or 229.

 {Grouping:} In some situations, you do not want to monitor a single
 interface but a group of interfaces that together form a pool.
 This check supports such pools by defining groups. The data of all members is
 accumulated and put together in a single grouped interface service.

cluster:
 In the case where single (ungrouped) interfaces are clustered, the corresponding
 services report only the results from the node with the highest outgoing traffic,
 since this node is likely the active node.
 In the case where interface groups are clustered, the grouping is applied across
 all nodes, potentially combining interfaces from different nodes. Note that the
 rules defining the interface groups must be configured to apply to the nodes, not
 to the cluster host (the latter has no effect). In case the grouping configurations
 vary across the nodes, the last node wins.
