A network administrator is configuring route summarization for received routes before advertising to the next peer with the commands:
R1(config)# router bgp 65500 R1(config-router)# aggregate-address 172.16.0.0 255.255.240.0 as-set summary-only R1(config-router)# end
How will the aggregate route be advertised after the commands are entered?
- The aggregate route will be advertised with previous BGP path information.
- The aggregate route will be advertised together with the smaller component network prefixes.
- The aggregate route will be advertised as an atomic aggregate route.
- The advertised aggregate route will increase the hop counts as it indicates multiple autonomous systems.
Explanation: Route summarization on BGP edge routers via dynamic method is configured by specifying an aggregation network prefix. The aggregate-address command advertises the aggregated route in addition to the specific original component network prefixes. By using the optional summary-only keyword, the component network prefixes in the summarized network range are suppressed. When a BGP router summarizes a route, it does not advertise the AS_Path information from before the aggregation. This is indicated by the atomic aggregate attribute. To keep the BGP path information history, the optional as-set keyword may be used with the aggregate-address command. The AS_Path settings from the original prefixes are stored in the AS_SET portion of the AS_Path. The AS_SET, which is displayed within brackets, only counts as one hop, even if multiple autonomous systems are listed.
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