This command shows the Ethernet switching table, which includes information about MAC addresses, their associated VLANs, and the interfaces they are learned on, similar to the output shown in your exhibit.

The maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation is
1476 bytes. This is because GRE packets are formed by the addition of the original packets and the required GRE headers. These headers are 24-bytes in length and since these headers are added to the original frame, depending on the original size of the packet we may run into IP MTU problems. The most common IP MTU is 1500-bytes in length (Ethernet). When the tunnel is created, it deducts the 24-bytes it needs to encapsulate the passenger protocols and that is the IP MTU it will use. For example, if we are forming a tunnel over FastEthernet (IP MTU 1500) the IOS calculates the IP MTU on the tunnel as: 1500-bytes from Ethernet-24-bytes for the GRE encapsulation = 1476-Bytes.

"The ENCAPSULATOR does not change the inner IP header, except to decrement the TTL and it remains unchanged during its deliver to the endpoint" - only router that encapsulates the inner packet decrements its TTL - during transit, the inner packet is unchanged.