Avoiding Routing Loops in Mutual Redistribution of OSPF Networks
Question
Your design plan includes mutual redistribution of two OSPF networks at multiple locations, with connectivity to all locations in both networks.
How is this accomplished without creating routing loops?
Answers
Explanations
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A. B. C. D.D.
In a network with multiple locations and OSPF networks, mutual redistribution can be used to enable communication between the networks. Mutual redistribution is a process where routes learned from one routing protocol are distributed into another routing protocol and vice versa.
However, mutual redistribution can create routing loops if not implemented carefully. A routing loop occurs when a packet is continuously forwarded between routers without reaching its destination. This can happen if there are multiple paths between two locations and the routers cannot decide which path to take.
To avoid routing loops in mutual redistribution, route maps can be used on the ASBRs (Autonomous System Boundary Routers). ASBRs are routers that connect one OSPF network to another OSPF network or to a different routing protocol.
Option A suggests using route maps on the ASBRs to allow only internal routes to be redistributed. Internal routes are OSPF routes that are learned within the same OSPF area. This option is a good choice because it prevents external routes (routes learned outside the OSPF network) from being redistributed, which could cause routing loops.
Option B suggests using route maps on the ASBRs to allow internal and external routes to be redistributed. This option is not recommended because it could result in routing loops if external routes are redistributed back into the same OSPF network.
Option C suggests using route maps on the ASBRs to set tags for redistributed routes. This option allows the ASBRs to differentiate between internal and external routes, but it does not prevent routing loops.
Option D suggests using route maps on the ASBRs to filter routes with tags so they are not redistributed. This option is also a good choice because it prevents routes with specific tags from being redistributed, which can prevent routing loops.
In conclusion, option A and D are both good choices for avoiding routing loops in mutual redistribution. Option A allows only internal routes to be redistributed, while option D allows the ASBRs to filter routes with tags to prevent redistribution.
