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ccna 0.The MTU size defines the per-interface setting that the router uses for its Layer 3 forwarding logic, specifying the maximum number of network layer packets that the router forwards outbound through each interface. For example, the MTU size for an IPv4 interface defines the maximum number of IPv4 packets that the router can forward outbound from a particular interface.The router always uses the default MTU size (1500 bytes), but it also has the ability to modify this value. The ipmtusize interface subcommand defines the MTU setting for IPv4. the ipv6 mtu size command also has the ability to define the MTU value for IPv6 packets.In an older variation, two OSPFV2 routers are actually able to become OSPF neighbors and reach a bidirectional (2-way) state, even if they happen to use different IPv4 MTU settings on their interfaces. However. they are also unable to exchange LSDBs. and finally. the neighbor relationship dissolves when their attempts to exchange LSDBs fail.These concepts that are implicitly behind MTU mismatch are equally valid in OSPFv2 and OSPFv3. An example of an OSPFv3-specific problem is given in the "OSPFv3 LSA Troubleshooting" section of Chapter 17. For more details on this issue, read that section.11.3 Preparing for the Exam11.3.1 Reviewing Exam EssentialsNote the "Exam Points" symbols in the margins of this chapter; these are the key review points for this chapter. Table 11-5 lists the content of these exam points.Table 11-5 Chapter 11 Exam EssentialsList Two things that happen when EIGRP or OSPF is enabled on an interface of a routerTable 11-1 List of 3 Commands Used to Determine Which Interface Enables EIGRP or OSPF