The value of configuration register instructs the boot program of a router to boot to the ROMMON prompt. This is equivalent to interrupting the router boot process by pressing Ctrl + Break .

Cisco's default configuration register is 0x2102.

• Step 1 : Change the routers configuration register to 0x2142.
• Step 2 : Reboot the router
• Step 3 : Upon reboot, exit from the setup mode
• Step 4 : Enable privileged Exec mode.
• Step 5 : Now Load the startup configuration by manually from NVRAM to RAM.
• Step 6 : Then Enable global configuration mode.
• Step 7 : And now change the passwords of a router
• Step 8 : After reseting the passwords now save the running config as a startup config in NVRAM.
• Step 9 : Now change the configuration register to its default value of 0x2102.
• Step 10: Now reboot the router and enter the router with the new passwords.

These are the advantages :
>> Low maintenance
>> Accuracy
>> Scalability

Maximum Transmission Unit (MTU) is a size of each data packets in bytes. Each network route has a certain MTU value. If higher MTU size means we can transfer more data at once.

Specifically EIGRP protocol considers the MTU metric to pick the best network routes by prefering routes with higher MTU.