On the SR Linux, an interface is any physical or logical port through which packets can be sent to or received from other devices.
The SR Linux supports the following interface types:
On the SR Linux, each loopback, network, management, and IRB interface can be subdivided into one or more subinterfaces. See Subinterfaces.
Every loopback, network, and management interface has an underlying interface in the Linux OS. These interfaces have names that adhere to Linux restrictions (maximum 15 characters and no slashes). The Linux interface name formats are as follows:
The following example shows a configuration for interface basic parameters, including administratively enabling the interface, specifying a description, and setting the MTU. The settings apply to any subinterfaces on the port, unless overridden in the subinterface configuration.
Example:
On the SR Linux, each loopback, network, management, and IRB interface can be subdivided into one or more subinterfaces. A subinterface is a logical channel within its parent interface.
Traffic belonging to one subinterface can be distinguished from traffic belonging to other subinterfaces of the same port using encapsulation methods such as 802.1Q VLAN tags.
While each port can be considered a shared resource of the router that is usable by all network-instances, a subinterface can only be associated with one network-instance at a time. To move a subinterface from one network-instance to another, you must disassociate it from the first network-instance before associating it with the second network-instance. See Network-instances.
You can configure ACL policies to filter IPv4 and/or IPv6 packets entering or leaving a subinterface. See Access control lists.
The SR Linux supports policies for assigning traffic on a subinterface to forwarding classes or remarking traffic at egress before it leaves the router. DSCP classifier policies map incoming packets to the appropriate forwarding classes, and DSCP rewrite-rule policies mark outgoing packets with an appropriate DSCP value based on the forwarding class. See Quality of service.
SR Linux subinterfaces can be specified as type routed or bridged:
Routed subinterfaces allow for configuration of IPv4 and IPv6 settings, and bridged subinterfaces allow for configuration of bridge table and VLAN ingress/egress mapping.
The CLI name of a subinterface is the name of its parent interface followed by a dot (.) and an index number that is unique within the scope of the parent interface. For example, the subinterface named ethernet-2/1.0 is a subinterface of ethernet-2/1, and it has index number 0.
The Linux name of a subinterface adheres to Linux restrictions (maximum 15 characters and no slashes). For example, the subinterface named ethernet-2/1.0 has the Linux name e2-1.0.
For IPv4 packets to be sourced from a subinterface, the IPv4 address family must be enabled on the subinterface and the subinterface must be configured with an IPv4 address and prefix length that indicates the other IPv4 hosts reachable on the same subnet. Likewise, in order for IPv6 packets to be sourced from a subinterface, the IPv6 address family must be enabled on the subinterface, which must be configured with a global unicast IPv6 address and prefix length. The address can be configured statically or obtained from a DHCP server.
Example:
The following example configuration shows basic parameters for a subinterface, including IPv4 (obtained through DHCP) and IPv6 (statically configured) addresses and prefix lengths. The example administratively enables the subinterface, specifies an ACL policy for input IPv4 traffic, and specifies a DSCP classifier policy that assigns input IPv4 traffic to a queue based on the 6-bit DSCP value in the IP header.
When the vlan-tagging parameter is set to true for a network interface, the interface can accept ethertype 0x8100 frames with one or more VLAN tags. The interface can be configured with up to 4096 subinterfaces, each with a separate index number.
Example:
The following example enables VLAN tagging for an interface and configures two subinterfaces. Single-tagged packets received on subinterface ethernet-2/1.1 are encapsulated with VLAN ID 101.
Bridged subinterfaces are associated with a mac-vrf network instance.
Example:
The following example shows the configuration for a bridged subinterface.
Integrated routing and bridging (IRB) interfaces enable inter-subnet forwarding. Network instances of type mac-vrf are associated with a network instance of type ip-vrf via an IRB interface.
On SR Linux, IRB interfaces are named irbN, where N is 0 to 255. Up to 4095 subinterfaces can be defined under an IRB interface. An ip-vrf network instance can have multiple IRB subinterfaces, while a mac-vrf network instance can refer to only one IRB subinterface.
IRB subinterfaces are type routed and cannot be configured as any other type.
IRB subinterfaces operate in the same way as other routed subinterfaces, including support for the following:
IRB interfaces do not support sFlow or VLAN tagging.
The following example configures an IRB interface. The IRB interface is operationally up when its admin-state is enabled, and its IRB subinterfaces are operationally up when associated with mac-vrf and ip-vrf network instances. At least one IPv4 or IPv6 address must be configured for the IRB subinterface to be operationally up.
Use the show interface command to display the operational state of configured interfaces.
Examples:
To display the status of all configured interfaces that have operational state up and their subinterfaces that also have operational state up:
To display summary information about interfaces that have operational state up or down:
To display summary information about a specific interface:
To display summary information about interfaces and subinterfaces that have operational state up or down:
To display summary information about a specific interface and its subinterfaces:
To display detailed information about a specific interface and its subinterfaces:
To display information about egress queues and Virtual Output Queues (VOQs) for a specific interface and its subinterfaces:
To display statistics for a specific interface, use the info from state command in candidate or running mode, or the info command in state mode.
Example:
You can clear the statistics counters for a specified interface.
Examples:
To clear queue statistics for an interface:
To clear statistics for a specified queue on an interface:
To display statistics for a specific subinterface, enter the context for the subinterface and use the info from state command.
Example:
You can clear the statistics counters for a specified subinterface.
Example:
A Link Aggregation Group (LAG), based on the IEEE 802.1ax standard (formerly 802.3ad), increases the bandwidth available between two network devices, depending on the number of links installed. A LAG also provides redundancy in the event that one or more links participating in the LAG fail. All physical links in a given LAG links combine to form one logical interface.
Packet sequencing is maintained for any given session. The hashing algorithm deployed by SR Linux is based on the type of traffic transported to ensure that all traffic in a flow remains in sequence, while providing effective load sharing across the links in the LAG.
LAGs can be either statically configured, or formed dynamically with Link Aggregation Control Protocol (LACP). Load sharing is executed in hardware, which provides line rate forwarding for all port types. A LAG can consist of ports of the same speed, as well as ports of mixed speed.
LAGs are supported on 7250 IXR (J2) systems only. SR Linux supports up to 128 LAG instances per system; each LAG instance can have up to 64 member links.
SR Linux supports configuring a min-link threshold for a LAG, which sets the minimum number of member links that must be active in order for the LAG to be operationally up. If the number of active links falls below this threshold, the entire LAG is brought operationally down.
If the min-link threshold is crossed, the active member links are maintained, including continuing to run LACP on links where it is configured, but the LAG is held out of forwarding state. Once the number of active links reaches or exceeds the min-link threshold, the LAG is brought back up operationally.
LACP, defined by the IEEE 802.3ad standard, specifies a method for two devices to establish and maintain LAGs. When LACP is enabled, SR Linux can automatically associate LACP-compatible ports into a LAG.
Normally all non-failing links in a LAG are active, and traffic is load-balanced across the active links. However, under some circumstances this is not desirable. Instead, it may be necessary for only some of the links to be active (for example, if all links are on the same IOM), while the other links are kept in standby. LACP allows you to select active links for a LAG based on particular constraints. This feature is based on the IEEE 802.1ax standard, so interoperability is ensured.
When LACP is enabled, LACP changes are visible through traps and log messages logged against the LAG.
To configure a LAG, you specify LAG parameters within the context of a LAG interface, then associate Ethernet interfaces with the LAG interface.
The MAC address of the LAG should be a unique value taken from the chassis MAC address pool.
Member links in the LAG can be associated statically or dynamically.
A LAG instance can consist of static links only or dynamic links only.
If an Ethernet interface is associated with a LAG interface, the following parameters must be the same for all associated Ethernet ports:
Example:
The following example shows the configuration for a LAG consisting of three member links.
The min-link threshold specifies the minimum number of member links that must be active in order for the LAG to be operationally up. If the number of active links falls below this threshold, the entire LAG is brought operationally down.
Example:
The following example configures the min-link threshold for a LAG to be 4. If the number of active links in the LAG drops below 4, the LAG is taken operationally down.
After the LAG has been taken operationally down due to crossing the min-link threshold, if the number active links in the LAG subsequently reaches 4 or higher, the LAG is brought operationally up. The default for the min-link threshold is 0 (disabled)
When LACP is enabled, SR Linux can automatically associate LACP-compatible ports into a LAG.
Example:
The following example configures LACP to run on an interface, which can dynamically become a member of a LAG:
In this example, the LACP interval is set to FAST, which causes LACP messages to be sent every second. The SLOW option for LACP interval causes LACP messages to be sent every 30 seconds.
To display statistics for a LAG interface, use the info from state command in candidate or running mode, or the info command in state mode.
Example:
You can clear the statistics counters for a specified LAG interface.
Examples:
To clear statistics for a LAG interface and all member links: