Nonstop Forwarding Awareness; Enabling Bgp Routing - Cisco WS-CBS3032-DEL Software Configuration Manual

Configuring BGP

Nonstop Forwarding Awareness

The BGP NSF awareness feature is supported for IPv4 in the IP services feature set. To enable this
feature with BGP routing, you need to enable graceful restart. When the neighboring router is
NSF-capable, and this feature is enabled, the Layer 3 switch continues to forward packets from the
neighboring router during the interval between the primary route processor in a router failure and the
backup route processor take-over, or while you manually reload the primary route processor for a
nondisruptive software upgrade.
For more information, see the "BGP Nonstop Forwarding (NSF) Awareness" section of the Cisco IOS
IP Routing Protocols Configuration Guide, Release 12.4.

Enabling BGP Routing

To enable BGP routing, you establish a BGP routing process and define the local network. Because BGP
must fully recognize the relationships with its neighbors, you must also specify a BGP neighbor.
BGP supports two kinds of neighbors: internal and external. Internal neighbors are in the same
autonomous system; external neighbors are in different autonomous systems. External neighbors are
usually adjacent to each other and share a subnet, but internal neighbors can be anywhere in the same
autonomous system.
The switch supports the use of private autonomous-system numbers, usually assigned by service
providers and given to systems whose routes are not advertised to external neighbors. The private
autonomous-system numbers are from 64512 to 65535. You can configure external neighbors to remove
private autonomous-system numbers from the autonomous-system path by using the neighbor
remove-private-as router configuration command. Then when an update is passed to an external
neighbor, if the autonomous-system path includes any private autonomous-system numbers, these
numbers are dropped.
If your autonomous system will be passing traffic through it from another autonomous system to a third
autonomous system, it is important to be consistent about the routes it advertises. If BGP advertised a
route before all routers in the network learned about the route through the IGP, the autonomous system
might receive traffic that some routers could not yet route. Therefore, BGP must wait until the IGP has
propagated information across the autonomous system so that BGP synchronizes with the IGP.
Synchronization is enabled by default. If your autonomous system does not pass traffic from one
autonomous system to another autonomous system, or if all routers in your autonomous systems are
running BGP, you can disable synchronization, which allows your network to carry fewer routes in the
IGP and allows BGP to converge more quickly.
To enable BGP, the switch or stack master must be running the IP services feature set.
Note
Beginning in privileged EXEC mode, follow these steps to enable BGP routing, establish a BGP routing
process, and specify a neighbor:
Command
Step 1
configure terminal
Step 2 ip routing
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
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Chapter 39
Purpose
Enter global configuration mode.
Enable IP routing (required only if IP routing is disabled).
Configuring IP Unicast Routing
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