Minimum Links - Cisco ASR 5000 Series Administration Manual

System Settings
Important
Each system that participates in link aggregation has a unique system ID that consists of a two-byte priority
(where the lowest number [0] has the highest priority) and a six-byte MAC address derived from the first
port's MAC address. The following command sets the system priority used to form the system ID. P is a hex
in the range [0x0000..0xFFFF]. The default is 0x8000.
card slot#
link-aggregation system-priority P
Ports in a system are assigned keys. The group number maps directly to the key, whereupon only ports with
the same key can be aggregated. Ports on each side of the link use a different aggregation key.
The system ID, port key and port ID of two peers form the Link Aggregation Group Identifier (LAGID). You
can aggregate links having the same LAGID. Systems are often configured initially with each port in its own
aggregation (requiring a separate key per port), or with all ports in the same aggregation (a single key for all
ports). Negotiation via LACP would qualify the actual aggregation.
Systems exchange information about system ID, port key and port ID with peers across the physical links
using LACP.
LACP packets are defined with the Slow Protocol format. Each system sends out its own ("actor") information
and its last received information about its peer ("partner") over the physical link.
Use the following commands to set the LACP parameters. LACP can run in active mode to send LACP packets
periodically, or in passive mode, in which it only responds to LACP packets it receives.
LACP can send packets at either a auto (30s) or fast (1s) rate. The defaults for this release are Active and
Auto; see the sample configuration below:
config
port ethernet slot#/port#
link-aggregation lacp { active | passive } [ rate { auto | fast } | timeout { long | short } ]
Peers send out LACP packets when the state changes or if a difference is found from a received LACP packet
about its own state.
Corresponding ports on an MIO/UMIO/MIO2 redundant pair cannot be active at the same time. Redundant
ports share the same MAC address, so after a failover is resolved, the original port rejoins the link aggregation
group.

Minimum Links

A minimum links option specifies that a Link Aggregation Group (LAG) is up (usable) only when a minimum
number of links are available for aggregation. This guarantees that a minimum amount of bandwidth is available
for use.
When this feature is enabled, a LAG is not usable when the number of links in a LAG goes below the configured
min-link value. Switchover to another LAG bundle (if available) automatically occurs when the number of
links in the current active bundle goes below the configured min-link value.
Use the min-link keyword option in the Global Configuration mode link-aggregation command to enable
this feature.
configure
port ethernet slot/port
The VPN can only bind the master port, and a VLAN can only be created on the master port. A failure
message is generated if you attempt to bind to a link aggregation member port.
ASR 5500 System Administration Guide, StarOS Release 21.4
Minimum Links
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