Eliminating the Need for AS Override in BGP Configuration for PE-CE Routing Protocol
Question
BGP is used for PE-CE routing protocol and all CEs in the same VPN use the same AS number.
Which command can be applied on PE router that eliminates the need to configure the AS override feature for the service provider in order to provide full connectivity amongst all CEs in the same VPN?
Answers
Explanations
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A. B. C. D.A.
In this scenario, all customer edge routers (CEs) in the same VPN use the same autonomous system (AS) number. This means that BGP will not advertise prefixes received from one CE to another within the same VPN unless an AS override feature is configured on the provider edge (PE) router. AS override forces the PE router to advertise the received prefixes from one CE to another CE within the same VPN even if the AS number is the same.
However, the question asks for a command that can be applied on the PE router to eliminate the need for AS override. The command that can accomplish this is the "neighbor allowas-in" command. This command allows the PE router to accept updates from the CE routers that contain the same AS number as the PE router. By default, BGP ignores updates that contain its own AS number in the AS_PATH attribute. The "neighbor allowas-in" command tells BGP to accept these updates, thereby allowing the PE router to advertise prefixes received from one CE to another CE within the same VPN.
Therefore, the answer to the question is A. neighbor allowas-in. The other options, B. neighbor SoO, C. maximum-paths ibgp maximum-number, and D. neighbor internal-vpn-client, are not related to the issue of advertising prefixes within the same VPN with the same AS number.
