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Configuring Fate Sharing

To configure fate sharing, include the fate-sharing statement:




fate-sharing {


group group-name {
cost value;

from address <to address>;
}


}

For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.

Each fate-sharing group must have a name, which can be up to 32 characters long and can contain letters, digits, periods (.) and hyphens (-). You can define up to 512 groups.

Fate-sharing groups contain three types of objects:

Point-to-point links—Identified by the IP addresses at each end of the link. Unnumbered point-to-point links are typically identified by borrowing IP addresses from other interfaces. Order is not important; from 1.2.3.4 to 1.2.3.5 and from 1.2.3.5 to 1.2.3.4 have the same meaning.
Non-point-to-point links—Include links on a LAN interface (such as Gigabit Ethernet interfaces) or nonbroadcast multiaccess (NBMA) interfaces (such as Asynchronous Transfer Mode [ATM] or Frame Relay). You identify these links by their individual interface address. For example, if the LAN interface 192.168.200.0/24 has four routers attached to it, each router link is individually identified:
from 192.168.200.1; # LAN interface of router 1

from 192.168.200.2; # LAN interface of router 2

from 192.168.200.3; # LAN interface of router 3

from 192.168.200.4; # LAN interface of router 4

You can list the addresses in any order.
A router node—Identified by its configured router ID.

All objects in a group share certain similarities. For example, you can define a group for all fibers that share the same fiber conduit, all optical channels that share the same fiber, all links that connect to the same LAN switch, all equipment that shares the same power source, and so on. All objects are treated as /32 host addresses.

For a group to be meaningful, it should contain at least two objects. You can configure groups with zero or one object; these groups are ignored during processing.

An object can be in any number of groups, and a group can contain any number of objects. Each group has a configurable cost attributed to it, which represents the level of impact this group has on CSPF computations. The higher the cost, the less likely a backup path will share with the primary path any objects in the group. The cost is directly comparable to traffic engineering metrics. By default, the cost is 1. Changing the fate-sharing database does not affect established LSPs until the next reoptimization of CSPF. The fate-sharing database does influence fast-reroute computations.

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