notes: BGP conditional Route Injection

- Provides a method to originate a prefix into a BGP routing table without the corresponding match in the IGP.
- Only prefixes that are equal to or more specific that the original prefix may be injected.
- This is used to improve the accuracy of route aggregation, by conditionally injecting or replacing less specific prefixes with more specific prefixes.

configuration set:

- The route to be monitored
ip prefix-list ROUTE permit 10.1.1.0/24
!
- The advertising source
ip prefix-list ROUTE_SOURCE permit 10.2.1.1/32
!
- The more specific routes to be injected

ip prefix-list ORIGINATE_ROUTES permit 10.1.1.0/25

ip prefix-list ORIGINATE_ROUTES permit 10.1.1.128/25

!
- Watches the monitored prefix in the RIB
- Matches the prefix learned from a specific source

route-map LEARNED_PATH permit 10

match ip address prefix-list ROUTE

match ip route-source prefix-list ROUTE_SOURCE
!
- Specifies the specifics to inject
- Sets optional parameters

route-map ORIGINATE permit 10

match ip address prefix-list ORIGINATE_ROUTES

set community 14616:555 additive
!
- Applies conditional route injection

router bgp 374

bgp inject-map ORIGINATE exist-map LEARNED_PATH

commands:

router bgp {asn}

bgp inject-map {map} exist-map {map} [copy-attribute]

- inject-map : Defines the prefixes which will be created and installed into the local BGP table
- exist-map : Specifies the prefix which the BGP speaker will track
- copy-attr : Config the injected route to inherit the attributes from the tracked route