what is the use of this command?
no service pad
logging buffered 51200 warnings
logging console critical
The packet assembler/disassembler (PAD) service supports X.25 links. This service is on by default, but it is not needed unless your router is using X.25. Disable it from global configuration mode as shown below.
TCP-KEEPALIVES-IN and TCP-KEEPALIVES-OUT
if you are going to permit remote administration via Telnet, enable TCP keepalive services. These services will cause the router to generate periodic TCP keepalive messages, thus allowing it to detect and drop orphaned (broken) TCP connections to/from remote systems. Using this service does not remove the need for setting an exec-timeout time as recommended above.
LOGGING BUFFERED 51200 WARNINGS
To turn ON buffered logging for warning messages. Rule of thumb, you should set it to 16K if your router has 16MB RAM. If you set it higher (i.e. 50K), make sure your router has more than 16MB RAM or at least 64MB RAM
LOGGING CONSOLE CRITICAL
To turn ON console logging for critical messages.
for more on securing cisco IOS/Router, check this link http://www.nsa.gov/snac/