link

Places CNA into service provider access link configuration mode to configure a link; or, associates an existing link with a USTAT module.

link <name>
 
link <name> 
 
     <max-avoidance> 
 
     [ start-avoidance percent-below-max <value> ]
 
no link
 
no link <name>
 

• name--name of link; can contain any combination of alpha-numerics, dash, and underscore.
• max-avoidance--(only when configuring load optimization threshold tables) level of usage (in megabits per second) at which the probability of a link being removed from the winner set is at its maximum; range: 0 through 1,000,000
• value--(only when configuring load optimization threshold tables) low end of avoidance threshold, expressed as a percentage below max_avoidance; range: 0 through 100

The link command is valid on any of the following configuration modes:

• config-engine--create a new service provider link or change parameters of an existing link
• config-engine-linkgroup--add a configured link to a link group
• config-engine-threshold-level--configure parameters in a load threshold table
• config-ustat--associate a configured link with a USTAT module

All modes requires privileged-level access.

May be used multiple times, once per service provider access link.

The link command is used in five different contexts:

• config-engine mode--defines a service provider access link in the CNA configuration
• config-ustat mode--associates a configured service provider access link with a USTAT module to associate the specified link with the USTAT module being configured.
• config-engine-threshold-level mode--defines load optimization parameters for a configured link.
• config-engine-linkgroup mode--associates a configured link with a link group, for active-measurement probes
• config-engine-billing mode--associates one or more configured links with a billing link

In config-engine mode, the link command puts CNA into link configuration mode (config-engine-link). Use the provider-as command to set the link’s AS number and IP address and the optional description and penalty commands to set a descriptive test field and weight links relative to each other (see winner-set-width command).

When adding links to the CNA configuration, you must fully configure a link. The CNA decision-maker process will not start properly if your configuration includes a partially configured link. If the system is booted with an incomplete link, you should use the medic call command to manually restart the decision-maker process when the link has been fully configured.

In general, exercise the following precautions with respect to link configurations:

• No two link definitions in the engine module should have the same peering address.
• A link reference in a USTAT blade should always point to a well-defined link in the engine module.
• All USTAT blades should have a VIP defined.
• The link reference in a neighbor definition should point to a well-defined link in the engine module.
• The group of links that are referred to in all neighbor definitions in the engine module should be the same as the group of all links defined in the engine module. (Note that neighbors can still be linkless, that is, not all neighbors must have a link reference.)

When configuring load threshold tables, the following restrictions should be observed:

• Polling usage must be enabled for all links referenced in threshold tables.
• Polling usage must not be enabled for any configured links that are not referenced in the tables.
• All tables must reference the same set of links.

If multiple USTATs are configured to point to the same link (a means of increasing measurements for an important set of prefixes, as in a VPN), the threshold configured by the outage-detection active-probe command will be divided among the USTATs. For example, if you configure the service provider link provider_a to be associated with both ustat_x and ustat_y and you have set your probe-failure threshold to 20, the CNA decision-maker process will declare a prefix outage after 10 probe failures on each of the two USTATs.

Use the no form of the command without a link name argument while in config-ustat mode to remove the association between the USTAT module and its associated link.

Use the no form of the command with a link name argument while in config-engine-threshold-level mode to remove the link from the load threshold table row.

Use the no form of the command with a link name argument while in config-engine-linkgroup mode to remove the link from the link group.