At which layer of the OSI model dose PPP perform?（）

What is the default administrative distance of OSPF?（）

Which name describes an IPV6 host-enable tunneling technique that uses IPV4 UDP,does not require dedicated gateway tunnels,and can pass through existing IPV4 NAT gateways?（）

While troubleshooting a network problem,a technician discovers that the current copy of the Cisco IOS is outdated and needs to be updated.Which of the following commands would the technician issue to replace the Cisco router IOS with the newer version?（）

Which command displays the CHAP authentication process as it occurs between two routers?（）

Which cisco ios command can help to determine the timing of various debug events,relative to each other,when you are debugging a complicated router issue?（）

What is the subnetwork address for a host with the IP address 201.100.5.68/28?（）

After the show ip route command has been entered,the follwing routes are displayed.Which route will not be entered into the routing table of a neighboring router?（）

Which Cisco IOS diagnostics command can disrupt the operation of a router under high-load conditions?（）

At which layer of the OSI model is RSTP used to prevent loops?（）