RAM / DRAM
The RAM is the current configuration and also reserves the ARP cache, fast-switching cache, the buffer occupied by the packets and the routing tables. RAM contents are lost at shutdown or reboot the router.
NVRAM
Not Volatile Ram. There is the startup configuration / backups, which contrary to what happens in RAM, this is not lost when shutdown or reboot the router.
Example.
If we change the IP address of the router, the new IP is saved in RAM, and then only momentarily (memory). In fact, if you turn off your router, restart meet again the old IP. This is because we have not saved the configuration in NVRAM.
If we want to save, we have to type from a privileged prompt copy running-config startup-config.
Example:
Router> en
Password: ******
Router # conf t
Enter configuration commands, one per line. End with CNTL / Z.
Router (config) #
Currently, the IP address of Ethernet interface 0 / 0 is 192.168.0.4 and 192.168.0.5 suppose we want to change:
Router (config) # interface ethernet 0 / 0
Router (config) # ip address 192.168.0.5 255.255.255.0
routerconfig) # end
Router #
Now we copy the current configuration in the startup configuration:
Router # copy running-config startup-config
Destination filename [startup-config]? (Enter)
Building configuration …
[OK]
Router #
Let’s reload the router:
# Reload
Now the settings have been saved. We can ping the IP 192.168.0.5 to verify it was changed or directly from the router:
# Sh int ethernet 0 / 0
Ethernet0 / 0 is up, line protocol is up
Hardware is AmdFE, address is 000b.5faa.60a0 (bia 000b.5faa.60a0)
Description: Eth
Internet address is 192.168.0.5/24
We note that the fact of our IP Ethernet interface 0 / 0 is 192.168.0.5
Flash
It is the permanent memory, contains the IOS (Internetworking Operating System). May contain multiple versions of IOS.
ROM
Statement of diagnostic software and the bootstrap (just needed to boot). To update this memory requires the removal and replacement of the CPU chip.
Auxiliary
Asynchronous port is mainly used for remote configuration and connection of additional devices.
Console
Asynchronous port also used to connect the router to the serial port of your PC.
Interfaces
Various interfaces are physically connected to the motherboard of the router or are real WIC (modules) through which packets enter and leave the router.