Refer to the exhibit.
Which statement about this device configuration is true?
Correct Answer: B
Explanation/Reference:
Explanation:
One of the most commonly used identifiers in SNMP-based network management applications is the Interface Index (ifIndex) value. IfIndex is a unique identifying number associated with a physical or logical interface. For most software, the ifIndex is the name of the interface. Although relevant RFCs do not require that the correspondence between particular ifIndex values and their interfaces be maintained across reboots, applications such as device inventory, billing, and fault detection depend on this correspondence.
Consider a situation where a simple monitoring software (like MRTG) is polling the interface statistics of the router specific serial interface going to the internet.
As an example, you could have these conditions prior to re-initialization:
physical port
ifIndex
ethernet port
tokenring port
serial port
Therefore, the management application is polling the ifIndex 3, which corresponds to the serial port.
After the router re-initialization (reboot, reload and so on) the conditions change to something similar to this:
physical port
ifIndex
ethernet port
tokenring port
serial port
The management application continues polling the ifIndex 3, which corresponds now to the ethernet port.
Therefore, if the management application is not warned by a trap, for example, that the router has been rebooted, the statistics polled could be completely wrong.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/simple-network-management-protocol- snmp/28420-ifIndex-Persistence.html