Question 1

How many usable host addresses are available in a /27 subnet?

Accepted Answer

30 — A /27 leaves 5 host bits (32 − 27). 2^5 = 32 total addresses; subtract the network and broadcast addresses to get 30 usable hosts.

Question 2

Which IPv6 address is the loopback address?

Accepted Answer

::1/128 — ::1/128 is the IPv6 loopback, equivalent to 127.0.0.1 in IPv4. fe80::/10 is link-local, ff02::1 is the all-nodes multicast group, and 2000::/3 is the global unicast range.

Question 3

What is the default administrative distance of OSPF?

Accepted Answer

110 — OSPF has an administrative distance of 110. Directly connected is 0, static is 1, EIGRP internal is 90, and RIP is 120. Lower AD is preferred when multiple sources offer the same prefix.

Question 4

A router receives a packet destined for a network that is not in its routing table and no default route exists. What does the router do?

Accepted Answer

Drops the packet — With no matching route and no gateway of last resort, the router drops the packet and (for ICMP) may return a destination-unreachable message. Routers never flood unknown unicast the way switches do.

Question 5

Which command assigns a switch access port to VLAN 20?

Accepted Answer

switchport access vlan 20 — After setting the port to access mode with switchport mode access, switchport access vlan 20 assigns it to VLAN 20. Trunk commands apply to 802.1Q trunk links, not access ports.

Question 6

In 802.1D spanning tree, which port state receives BPDUs but does not forward frames or learn MAC addresses?

Accepted Answer

Blocking — A blocking port only listens to BPDUs to maintain a loop-free topology; it does not forward frames or learn MACs. Learning ports build the MAC table but still do not forward; forwarding ports do both.

Question 7

Which EtherChannel mode actively negotiates a bundle using LACP?

Accepted Answer

active — active and passive are LACP modes; active initiates negotiation. desirable and auto are PAgP (Cisco) modes. on forces the channel with no negotiation and must be set on both ends.

Question 8

Which NAT variation maps many inside private addresses to a single public address by tracking port numbers?

Accepted Answer

PAT (NAT overload) — Port Address Translation, configured with the overload keyword, lets many hosts share one public IP by distinguishing sessions with unique source ports. Static NAT is one-to-one; dynamic NAT maps to a pool without port overloading.

Question 9

Place the DHCP DORA process in the correct order.

Accepted Answer

Discover, Offer, Request, Acknowledge — The client broadcasts a DHCPDISCOVER, the server replies with a DHCPOFFER, the client sends a DHCPREQUEST for the offered lease, and the server confirms with a DHCPACK.

Question 10

Following best practice, where should a standard ACL be applied?

Accepted Answer

As close to the destination as possible — Standard ACLs filter on source address only, so placing them near the destination avoids unintentionally blocking traffic to other networks. Extended ACLs, which match source and destination, are placed near the source to drop unwanted traffic early.

Question 11

What is the default violation mode for switchport port security?

Accepted Answer

shutdown — The default violation mode is shutdown, which places the port in err-disabled state on a violation. protect silently drops offending frames, and restrict drops them while incrementing counters and sending an SNMP/syslog notification.

Question 12

Which data format uses key/value pairs enclosed in braces and is commonly returned by REST APIs on Cisco controllers?

Accepted Answer

JSON — JSON (JavaScript Object Notation) represents data as key/value pairs inside curly braces and is the default payload format for most REST APIs, including Cisco DNA Center's northbound API.

CCNA practice questions with answers

12 sample questions

How to use practice questions effectively