A co-worker is developing an implementation plan for a design that uses OSPF 2 and RIPv2
routing domains, with two routers redistributing between the two domains.
The co-worker asks your help in choosing how to prevent domain loops by setting
administrative distance. Assuming all other related settings use defaults, which of the
following would solve the domain loop problem?
A.
The distance ospf intra-area 80 inter-area 80 OSPF subcommand
B.
The distance ospf external 80 OSPF subcommand
C.
The distance ospf intra-area 180 inter-area 180 OSPF subcommand
D.
The distance ospf external 180 OSPF subcommand
Explanation:
AD can be used to prevent the domain loop problem with two routing domains by making
each routing protocol’s AD for internal routes be better (lower) than the other routing
protocol’s AD for external routes. RIP uses AD 120 for all routes, with no distinction of
internal or external. As such, OSPF’s internal default AD settings of 110 meet the
requirement that OSPF’s internal AD (110) is better than RIP’s external (120). However,
RIP’s default of 120 is not better than OSPF’s default for externals (110), so the distance
ospf external 180 command changes that setting to meet both requirements. The three
wrong answers, while syntactically valid, do not help meet the requirements.