问题：

[单选] How would you characterize the source and type in a denial of service attack on a router？（）

A . By perfornubg a show ip interface to see the type and source of the attack based upon the access-listmatches
B . By performing a show interface to see the transmitted load "txload" and receive load "rxload" ；if the interface utilization is not maxed out ，there is no attack underway
C . By setting up an access-list to permit all ICMP，TCP，and UDP traffic with the log or log-input commands，then use the show access-list and show log commands to determine the type and sourceof attack
D . By applying an access-list to all incoming and outgoing interfaces，turning off route-cache on all interfaces，then，when telnetting into the router perform a debug IP packet detail