Which two configuration changes can you make on edge-1 to allow the two routers to establish adjacency?

Refer to the exhibit. Router edge-1 is unable to establish OSPF neighbor adjacency with router ISP-1. Which two configuration changes can you make on edge-1 to allow the two routers to establish adjacency? (Choose two.)

200-105-interconnecting-cisco-networking-devices-part-2-icnd2-v3-0_img_039

A. Set the subnet mask on edge-1 to 255 255.255.252.
B. Reduce the MTU on edge-1 to 1514.
C. Set the OSPF cost on edge-1 to 1522.
D. Reduce the MTU on edge-1 to 1500.
E. Configure the ip ospf mtu-ignore command on the edge-1 Gi0/0 interface.

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4 thoughts on “Which two configuration changes can you make on edge-1 to allow the two routers to establish adjacency?

  1. option D or E alonne would not be sufficient for this to work we need to correct the mask as well but since that option is not availabe in the answer option so you should choose D and E on your exam if it says choose two options.

  2. https://en.wikipedia.org/wiki/Subnetwork:

    There is an exception to this rule for 31-bit subnet masks,[11] which means the host identifier is only one bit long for two permissible addresses. In such networks, usually point-to-point links, only two hosts (the end points) may be connected and a specification of network and broadcast addresses is not necessary.

  3. The question and/or answers are flawed because the two will not form an adjacency being configured on different subnets. Answer A would not solve the issue, at least with the answer listed.

    The MTU’s must both be the same or set to ignore, so answers D and E are also appropriate.

    As with any questionable Q&A, you should learn the concept rather than memorize answers.

  4. What about the 2 interfaces being on Different Networks. Since with that Mask (/31) only one IP Address is available per network. Hence 10.0.0.254 is one subnet and 10.0.0.255. And we have to remember that OSPFv2 requieres NEIGHBORS being in the same Subnet.

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