Last Updated on August 7, 2021 by Admin 3
You administer the network shown above.
You issue the show running-config command on RouterA and receive the following partial output:
Which of the following statements are true? (Select 2 choices.)
- RouterA will not advertise any routes to RouterB.
- RouterA will advertise only the route to 192.168.1.0/24 to RouterB.
- RouterA will advertise the routes to 192.168.0.0/24 and 192.168.1.0/24 to RouterB.
- RouterB will not advertise any routes to RouterD.
- RouterB will advertise only the route to 192.168.0.0/24 to RouterD.
- RouterB will advertise only the route to 192.168.1.0/24 to RouterD.
- RouterB will advertise the routes to 192.168.0.0/24 and 192.168.1.0/24 to RouterD.
RouterA will advertise the routes to 192.168.0.0/24 and 192.168.1.0/24 to RouterB, and RouterB will advertise only the route to 192.168.1.0/24 to RouterD. RouterB will advertise both routes to RouterC because RouterB and RouterC are in the same autonomous system (AS). The neighbor 10.1.1.2 routemap map1 out command applies route map map1 to modify outgoing routes from RouterA. Because the routemap map1 permit 20 command overrides the implicit deny rule for map1, the route map will not restrict which routes are advertised from RouterA to RouterB. Additionally, map1 is configured to only apply the noexport community attribute to routes that match access list 1. Routes that do not match access list 1 are advertised without the attribute. Because route map map1 is configured to apply the noexport community attribute to only the routes that pass access list 1, the noexport community attribute will affect only the route to 192.168.0.0/24.
The neighbor 10.1.1.2 remoteas 200 command specifies that RouterB, which is in AS 200, is an external Border Gateway Protocol (eBGP) neighbor of RouterA. The neighbor 10.1.1.2 sendcommunity command configures RouterA to send community attribute settings to RouterB. The community attribute is an optional, transitive Border Gateway Protocol (BGP) attribute that is not required to be supported by all BGP implementations. Additionally, BGP implementations that do not support the community attribute are not required to pass the attribute to other routers. By default, Cisco routers do not pass community attributes to BGP neighbors. The community attribute can be modified in a route map by issuing the set community command with one of the following four keywords:
-no-advertise -prevents advertisements to any BGP peer
-no-export-prevents advertisements to eBGP peers
-loca-las -prevents advertising outside the AS, or in confederation scenarios, outside the sub-AS internet-advertises the route to any router
The set community no-export command configures the BGP community attribute to inform neighbor routers to not export the route to eBGP peers. Therefore, RouterB will not advertise the route to 192.168.0.0/24 outside of AS 200. Because RouterD is in AS 300, RouterB will not advertise the 192.168.0.0/24 route to RouterD. RouterB will advertise both routes to RouterC, which is in AS 200. The community attribute does not modify how RouterA advertises the routes; it modifies how neighbor routers advertise the routes received from RouterA.