|
|
|
The CNA system is capable of asserting its choice of service provider to your edge routers, so that your traffic to end users within a given prefix will always use a route with a proven, measurable performance record. Asserted routes are also called performance routes. You can also associate decision policies with prefixes to instruct the CNA system to handle them the you want. For example, you might wish to give priority treatment to certain prefixes, or change the way certain traffic loads particular links. See Chapter 6: Decision Policies and Application Models of the CNA Basic Monitoring Guide.
The device can also operate in report-only mode, in which it will conduct traffic tests, analyze results and make choices among your service providers, but it will not assert these choices to your edge routers. You can monitor the CNA system’s performance by using the CLI show commands or by viewing reports using the CNA web interface.
When you are ready to allow the CNA system to direct traffic through your edge routers, you can place the device into route-assert mode by calling the route-assert-mode CLI command.
Use the no form of the command to suspend route-assert mode (all asserted routes will be withdrawn).
If you have an immediate need for corrective action but you don’t want to suspend route assertion, use the clear prefix command to manually withdraw asserted routes. You can choose whether the CNA database retains measurement counters when clearing prefixes. If you use the keyword routes-only with the command, routes will be cleared but measurement counts will be retained. If you omit the keyword, counters will be cleared and the CNA system will not resume asserting routes until prefixes again qualify as sufficiently measured, as defined by the min-required-measurements command.
Counters are not cleared when route-assert mode is disabled. When you re-enable route assertions, the decision making process will resume immediately as though route-assert mode had been continuous.
The CNA system will not assert a route if the router has already chosen the same route because of BGP. This may not be the desired behavior for certain customized network topologies. You can override this behavior by using the assert-routes-matching-bgp command. See the companion document, CNA Command Reference Guide, for more information about this command.
You can disable the CNA system’s default requirement that all edge routers know about a prefix before the CNA system will assert a route to it, by using the no form of the require-routes-from-all-routers command.
|
|
|