Free N10-009 flashcards

In the CompTIA methodology, what must a technician do with a freshly formed theory of probable cause before doing anything else?

Test the theory to confirm whether it is actually the cause. The method sequences theory work as establish, then test, then plan, then implement, so a change can only follow a tested and confirmed cause.

I already suspect a duplex mismatch, so the efficient move is to hard-code both interfaces to the same speed and duplex right away.

That is the eventual corrective action, but implementing a change comes only after the theory has been tested and a plan of action has been established. Jumping straight to the fix skips the required test step.

How do you work out how many usable host addresses a given IPv4 prefix provides, and why does a /29 give exactly six?

Take two raised to the number of host bits, then subtract two for the all-zeros network address and the all-ones broadcast address. A /29 leaves three host bits, so two to the third power is eight total addresses, minus two leaves six usable hosts.

A /28 sounds right for six usable hosts because it is one of the smaller subnets.

A /28 leaves four host bits, giving 16 addresses and 14 usable hosts. That is a single host bit too many and doubles the size needed; the requirement of six usable hosts is met by a /29, which leaves three host bits.

Two PCs on one switch sit in different VLANs on different subnets and each reaches its own VLAN but not the other. What kind of device must handle the traffic between them?

A Layer 3 device. Each VLAN is a separate broadcast domain mapped to its own IP subnet, so traffic between subnets must cross a Layer 3 boundary. A router subinterface or a multilayer switch SVI supplies that inter-VLAN gateway while the VLANs stay separate.

PC-A cannot reach PC-B in another VLAN, so I just need an 802.1Q trunk between the switchports to connect the two VLANs.

A trunk multiplexes several VLANs onto one switch-to-switch link so their tags survive the hop. It does not route packets from one VLAN subnet into another. Crossing subnets still needs a Layer 3 device.

Which SNMP version and security level encrypts both the login credentials and the message payload in transit?

SNMPv3 in authPriv mode. Its User-based Security Model authenticates the user and adds a privacy protocol such as AES on top, so both credentials and payload are encrypted. SNMPv1 and SNMPv2c rely on cleartext community strings and encrypt nothing.

A non-default read-only community string on SNMPv2c keeps the traffic private in transit.

A non-default community is safer than 'public', but SNMPv2c still carries the community string and message payload in cleartext, so nothing is encrypted on the wire. Confidentiality needs SNMPv3 authPriv.