Routing Policy Enforcement; Apply Policy When Updating Routing Table - Cisco NCS 5500 Series Configuration Manual

Implementing BGP
Example:
RP/0/RP0/CPU0:router(config)# router bgp 120
Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP
routing process.
Step 3 address-family { ipv4 | ipv6 } unicast
Example:
RP/0/RP0/CPU0:router(config-bgp)# address-family ipv4 unicast
Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.
To see a list of all the possible keywords and arguments for this command, use the CLI help (?).
Step 4 bgp dampening [ half-life [ reuse suppress max-suppress-time ] | route-policy route-policy-name ]
Example:
RP/0/RP0/CPU0:router(config-bgp-af)# bgp dampening 30 1500 10000 120
Configures BGP dampening for the specified address family.
Step 5 commit

Routing Policy Enforcement

External BGP (eBGP) neighbors must have an inbound and outbound policy configured. If no policy is
configured, no routes are accepted from the neighbor, nor are any routes advertised to it. This added security
measure ensures that routes cannot accidentally be accepted or advertised in the case of a configuration
omission error.
This enforcement affects only eBGP neighbors (neighbors in a different autonomous system than this
Note
router). For internal BGP (iBGP) neighbors (neighbors in the same autonomous system), all routes are
accepted or advertised if there is no policy.

Apply Policy When Updating Routing Table

The table policy feature in BGP allows you to configure traffic index values on routes as they are installed in
the global routing table. This feature is enabled using the table-policy command and supports the BGP policy
accounting feature. Table policy also provides the ability to drop routes from the RIB based on match criteria.
This feature can be useful in certain applications and should be used with caution as it can easily create a
routing 'black hole' where BGP advertises routes to neighbors that BGP does not install in its global routing
table and forwarding table.
Perform this task to apply a routing policy to routes being installed into the routing table.
BGP Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
Routing Policy Enforcement
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