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Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, NX-OS Release 5.0(3)U1(1)
Chapter 6 Configuring Advanced BGP
Information About Advanced BGP
• Next hop becomes a nonlocal address.
Note Reachability and recursed metric events trigger a best-path recalculation.
Event notifications from the RIB are classified as critical and noncritical. Notifications for critical and
noncritical events are sent in separate batches. However, a noncritical event is sent with the critical
events if the noncritical event is pending and there is a request to read the critical events.
• Critical events are related to the reachability (reachable and unreachable), connectivity (connected
and unconnected), and locality (local and nonlocal) of the next hops. Notifications for these events
are not delayed.
• Noncritical events include only the IGP metric changes.
See the “Configuring BGP Next-Hop Address Tracking” section on page 6-21 for more information.
Route Redistribution
You can configure BGP to redistribute static routes or routes from other protocols. You configure a route
policy with the redistribution to control which routes are passed into BGP. A route policy allows you to
filter routes based on attributes such as the destination, origination protocol, route type, route tag, and
so on. See Chapter 11, “Configuring Route Policy Manager,” for more information.
Tuning BGP
You can modify the default behavior of BGP through BGP timers and by adjusting the best-path
algorithm.
This section includes the following topics:
• BGP Timers, page 6-8
• Tuning the Best-Path Algorithm, page 6-8
BGP Timers
BGP uses different types of timers for neighbor session and global protocol events. Each established
session has a minimum of two timers for sending periodic keepalive messages and for timing out
sessions when peer keepalives do not arrive within the expected time. In addition, there are other timers
for handling specific features. Typically, you configure these timers in seconds. The timers include a
random adjustment so that the same timers on different BGP peers trigger at different times.
Tuning the Best-Path Algorithm
You can modify the default behavior of the best-path algorithm through optional configuration
parameters, including changing how the algorithm handles the MED attribute and the router ID.
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