One interface has a problem.
Two interfaces have problems.
The interfaces are functioning correctly.
The operational status of the interfaces cannot be determined from the output shown.
VLANs have not been created yet.
An IP address must be configured for the port.
The port is currently configured for access mode.
The correct encapsulation type has not been configured.
The no shutdown command has not been entered for the port.
The usernames are incorrectly configured on the two routers.
The passwords do not match on the two routers.
CHAP authentication cannot be used on a serial interface.
The routers cannot be connected from interface S0/0 to interface S0/0.
With CHAP authentication, one router must authenticate to another router. The routers cannot be configured to authenticate to each other.
The cable that is connected to S0/0 on RouterA is faulty.
Interface S0/0 on RouterB is administratively down.
Interface S0/0 on RouterA is configured with an incorrect subnet mask.
The IP address that is configured on S0/0 of RouterB is not in the correct subnet.
Interface S0/0 on RouterA is not receiving a clock signal from the CSU/DSU.
The encapsulation that is configured on S0/0 of RouterB does not match the encapsulation that is configured on S0/0 of RouterA.
Transmission unit size too large
No loopback set
An incorrect subnet mask
Incompatible encapsulation at each end
An incorrect IP address
Incompatible bandwidth between routers
HostA is not on the same subnet as its default gateway.
The address of SwitchA is a subnet address.
The Fa0/0 interface on RouterA is on a subnet that can’t be used.
The serial interfaces of the routers are not on the same subnet.
The Fa0/0 interface on RouterB is using a broadcast address.
There is no encapsulation type configured.
There is a mismatch in encapsulation types.
The interface is not receiving any keepalives.
The interface has been configured with the shutdown command.
The interface needs to be configured as a DTE device.
The wrong type of cable is connected to the interface.
The network administrator failed to save the configuration.
The configuration register is set to 0×2100.
The boot system flash command is missing from the configuration.
The configuration register is set to 0×2102.
The router is configured with the boot system startup command.