Cisco Certified Network Associate (CCNA)

Exam 200-301Cisco Certified Network Associate (CCNA 2021) Demo Questions

200-301: Cisco Certified Network Associate 2021 (Jun 2021) QUESTION 1 What is the primary function of a Layer 3 device? A. to forward traffic within the same broadcast domain B. to pass traffic between different networks C. to analyze traffic and drop unauthorized traffic from the Internet D. to transmit wireless traffic between hosts Answer: B

QUESTION 2 Which action does the route take as it forwards a packet through the network? A. The route encapsulates the source and destination IP addresses with the sending router IP address as the

source and the neighbor IP address as the destination B. The router encapsulates the original packet and then includes a tag that identifies the source router MAC

address and transmits it transparently to the destination C. The router replaces the original source and destination MAC addresses with the sending router MAC

address as the source and neighbor MAC address as the destination D. The router replaces source and destination labels with the sending router interface label as a source and the

next hop router label as a destination Answer: C

QUESTION 3 What are two reasons that cause late collisions to increment on an Ethernet interface? (Choose two) A. when the sending device waits 15 seconds before sending the frame again B. when the cable length limits are exceeded C. when one side of the connection is configured for half-duplex D. when Carrier Sense Multiple Access/Collision Detection is used E. when a collision occurs after the 32nd byte of a frame has been transmitted Answer: B, C

以 100 Mbps Ethernet 為例，在正常情況下傳送 64 byte (512 bit) 資料，只需要 5.12us 微秒 (microseconds 百萬分之一秒)，如果超出這個時間都未到達目的地的話，有可能是網絡超出 100 米的預設長度或出現Duplex Mismatch。如果傳送 64 byte 資料後所發生的 collision，我們會稱為 late collision。(因為正常的 collision 要發生的話只會在傳送後 5.12us 微秒內發生。) https://www.cisco.com/c/en/us/support/docs/interfaces-modules/port-adapters/12768-eth-collisions.html QUESTION 4 A device detects two stations transmitting frames at the same time. This condition occurs after the first 64 bytes of the frame is received. Which interface counter increments? A. collision B. late collision C. runt D. CRC Answer: B

QUESTION 5

Refer to the exhibit. An engineer must add a subnet for a new office that will add 20 users to the network. Which IPv4 network and subnet mask combination does the engineer assign to minimize wasting addresses? A. 10.10.225.48 255.255.255.240 B. 10.10.225.32 255.255.255.240 C. 10.10.225.48 255.255.255.224 D. 10.10.225.32 255.255.255.224 Answer: D 答案 A 和 B 不正確，因為當 subnet mask 係 255.255.255.240 的時侯，可用的 IP address 只有 14 個，不能滿足題目的需求 20 個 IP address。餘下的兩個答案 C 和 D，當 subnet mask 係 255.255.255.224 的時侯，只有 10.10.225.32 的網絡是其中一個的 subnet。 QUESTION 6 An office has 8 floors with approximately 30-40 users per floor. One subnet must be used. Which command must be configured on the router Switched Virtual Interface to use address space efficiently? A. ip address 192.168.0.0 255.255.0.0 B. ip address 192.168.0.0 255.255.254.0 C. ip address 192.168.0.0 255.255.255.128 D. ip address 192.168.0.0 255.255.255.224 Answer: B 這題說明 8 層樓每層最多 40 個 users，合共最多 320 個 IP address，而題目要求只需要 1 個 subnet，所要要用 255.255.255.254 作為 subnet mask 組成一個擁用最多 512 個 IP address 的 subnet 便可滿足要求。

QUESTION 7

Refer to the exhibit. An engineer booted a new switch and applied this configuration via the console port. Which additional configuration must be applied to allow administrators to authenticate directly to enable privilege mode via Telnet using a local username and password? A. R1(config)#username admin privilege 15 secret p@ss1234

R1(config-if)#line vty 0 4 R1(config-line)#login local

B. R1(config)#username admin R1(config-if)#line vty 0 4 R1(config-line)#password p@ss1234

C. R1(config)#username admin R1(config-if)#line vty 0 4 R1(config-line)#password p@ss1234 R1(config-line)#transport input telnet

D. R1(config)#username admin secret p@ss1234 R1(config-if)#line vty 0 4 R1(config-line)#login local R1(config)#enable secret p@ss1234

Answer: A

QUESTION 8

Refer to the exhibit. An administrator configures four switches for local authentication using passwords that are stored as a cryptographic hash. The four switches must also support SSH access for administrators to manage the network infrastructure. Which switch is configured correctly to meet these requirements? A. SW1 B. SW2 C. SW3 D. SW4 Answer: C

QUESTION 9 In which situation is private IPv4 addressing appropriate for a new subnet on the network of an organization? A. The ISP requires the new subnet to be advertised to the Internet for web services B. The network has multiple endpoint listeners, and it is desired to limit the number of broadcasts C. There is limited unique address space, and traffic on the new subnet will stay local within the organization D. Traffic on the subnet must traverse a site-to-site VPN to an outside organization Answer: C Private IP address (俗稱 "假 IP") 適合公司內部使用。

QUESTION 10 Which protocol requires authentication to transfer a backup configuration file from a router to remote server? A. TFTP B. FTP C. SMTP D. DTP Answer: B 當要將 Router/Switch 的 config file 備份時，使用 TFTP 是沒有密碼驗證功能，相反 FTP 可以做到密碼驗證。SMTP 是用作發送電郵，DTP (Dynamic Trunk Protocol) 是在 Switch 之間建立 Trunk link。 QUESTION 11 A packet is destined for 10.10.1.22. Which static route does the router choose to forward the packet? A. ip route 10.10.1.0 255.255.255.240 10.10.255.1 B. ip route 10.10.1.20 255.255.255.252 10.10.255.1 C. ip route 10.10.1.20 255.255.255.254 10.10.255.1 D. ip route 10.10.1.16 255.255.255.252 10.10.255.1 Answer: B 這題是考驗你 subnetting 技巧和設定 static route 指令的題目，如果 Packet 的目的地是 10.10.1.22，我們要選取答案 B，因為如果 subnet mask 是 255.255.255.252 的話，目的地 IP address 10.10.1.22 只可以在網絡 10.10.1.20 之中。所以答案 B 是正確。 QUESTION 12 Why does a switch flood a frame to all port? A. The source MAC address of the frame is unknown B. The frame has zero destination MAC addresses C. The destination MAC address of the frame is unknown D. The source and destination MAC addresses of the frame are the same Answer: C

QUESTION 13

Refer to the exhibit. Routers R1 and R2 have been configured with their respective LAN interfaces. The two circuits are operational and reachable across WAN. Which command set establishes failover redundancy if the primary circuit goes down? A. R1(config)# ip route 10.10.13.10 255.255.255.255 10.10.10.6

R2(config)# ip route 192.168.0.100 255.255.255.255 10.10.10.5

B. R1(config)# ip route 10.10.13.10 255.255.255.255 10.10.10.2 R2(config)# ip route 192.168.0.100 255.255.255.255 10.10.10.1

C. R1(config)# ip route 0.0.0.0 0.0.0.0 10.10.10.6 R2(config)# ip route 0.0.0.0 0.0.0.0 10.10.10.5

D. R1(config)# ip route 0.0.0.0 0.0.0.0 10.10.10.6 2 R2(config)# ip route 0.0.0.0 0.0.0.0 10.10.10.5 2

Answer: D

QUESTION 14

Refer to the exhibit. Which two prefixes are included in this routing table entry? (Choose two) A. 192.168.1.17 B. 192.168.1.61 C. 192.168.1.64 D. 192.168.1.127 E. 192.168.1.254 Answer: A, B 如果 network number 由 0 開始，/26 的 subnet IP address 範圍即是由 0 63，所以答案 A 和 B 是正確。

QUESTION 15 R1 has learned route 192.168.12.0/24 via IS-IS, OSPF, RIP and Internal EIGRP under normal operating conditions, which routing protocol is installed in the routing table? A. IS-IS B. RIP C. Internal EIGRP D. OSPF Answer: C 由於 EIGRP 的 AD 數值是四個選項中最細，所以 Router 會選擇 EIGRP 的路徑。

QUESTION 16 R1 has learned route 10.10.10.0/24 via numerous route protocols. Which route is installed? A. route with the lowest cost B. route with the lowest administrative distance C. route with the next hop that has the highest IP D. route with the shortest prefix length Answer: B Administrative Distance 管理距離是路由信息來源的可信賴級別。如果 Router 收到來自“多個”路由協議的 routing path，並且所有路徑都具有“相同”的 prefix length，就會比較 AD 數值並以最少的 AD 決定 routing path。 QUESTION 17 A router running EIGRP has learned the same route from two different paths. Which parameter does the router used to select the best path? A. cost B. as-path C. metric D. administrative distance Answer: C 如果 Router 發覺在 Routing table 內有“同一種”Routing Protocol 擁有多個一條的 routing path 去“同一個”網絡，Router 會根據 Metric 選擇路徑。 QUESTION 18

Refer to the exhibit. Which route does R1 select for traffic that is destined to 192 168.16.2? A. 192.168.16.0/21 B. 192.168.16.0/24 C. 192.168 16.0/26 D. 192.168.16.0/27 Answer: D 上面題目的 routing path 都是從不同的 Routing protocols 接收回來，但 prefix length 四個長度不同，分別為 /21, /24, /26, /27，由於 /27 是最長的 prefix length，所以 Router 會選擇第四行作首選的路徑 “i L1 192.168.16.0/27 [115/30] via 192.168.1.4” 處理有關 packet。 Reference: Route Selection in Cisco Routers https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/8651-21.html

QUESTION 19

Refer to the exhibit. A packet is being sent across router R1 to host 172.16.3.14. To which destination does the router send the packet? A. 207.165.200.246 via Serial0/1/0 B. 207.165.200.254 via Serial0/0/0 C. 207.165 200.254 via Serial0/0/1 D. 207.165.200.250 via Serial0/0/0 Answer: C 如果前往 host 172.16.3.14，Router 基於 longest subnet perfix 便會選擇 OSPF 這條路徑處理，即是這一行 "O 172.16.3.0/28 [110/84437] via 207.165.200.254, 00:00:28, Serial0/0/1" 而這個網絡 172.16.3.0/28 subnet 包含的 IP address 範圍是 0 15。 QUESTION 20

Refer to the exhibit. A packet is being sent across router R1 to host 172.16.0.14. To which destination does the router send the packet? A. 209.165.200.246 via Serial0/1/0 B. 209.165.200.254 via Serial0/0/0 C. 209.165 200.254 via Serial0/0/1 D. 209.165.200.250 via Serial0/0/0 Answer: A 這題小心和上一題混淆，圖片和答案選擇都有點不同。這題問如果前往 host 172.16.0.14，由於在 routing table 內沒有特定處理這個 network 的 routing path，所以最後會由 default route 處理，即是 S* 那一行，所以 Router 會交給 209.165.200.246 via Serial0/1/0 處理相關 packet。

QUESTION 21

Refer to the exhibit. Router R1 Fa0/0 cannot ping router R3 Fa0/1.Which action must be taken in router R1 to help resolve the configuration issue? A. set the default network as 20.20.20.0/24 B. configure a static route with Fa0/1 as the egress interface to reach the 20.20.20.0/24 network C. set the default gateway as 20.20.20.2 D. configure a static route with 10.10.10.2 as the next hop to reach the 20.20.20.0/24 network Answer: D R1 只須簡單地設定前往 20.20.20.0/24 的 static route 指向 next hop 10.10.10.2 便可。

QUESTION 22 A user configured OSPF and advertised the Gigabit Ethernet interface in OSPF By default, which type of OSPF network does this interface belong to? A. point-to-multipoint B. point-to-point C. broadcast D. nonbroadcast Answer: C

QUESTION 23 A user configured OSPF in a single area between two routers. A serial interface connecting R1 and R2 is running encapsulation PPP. By default which OSPF network type is seen on this interface when the user types show ip ospf interface on R1 or R2? A. port-to-multipoint B. broadcast C. point-to-point D. non-broadcast Answer: C

QUESTION 24 An engineer configured an OSPF neighbor as a designated router. Which state verifies the designated router is in the proper mode? A. Exchange B. 2-way C. Full D. Init Answer: C 雙方 router 成功完成 OSPF 的資料交換便進入 FULL state 狀態。

QUESTION 25 When OSPF learns multiple paths to a network, how does it select a route? A. It multiple the active K value by 256 to calculate the route with the lowest metric. B. For each existing interface, it adds the metric from the source router to the destination to calculate the route

with the lowest bandwidth. C. It divides a reference bandwidth of 100 Mbps by the actual bandwidth of the existing interface to calculate

the router with the lowest cost. D. It count the number of hops between the source router and the destination to determine the router with the

lowest metric Answer: C

QUESTION 26

Refer to the exhibit. The show ip ospf interface command has been executed on R1. How is OSPF configured? A. The interface is not participating in OSPF B. There are six OSPF neighbors on this interface C. The default Hello and Dead timers are in use D. A point-to-point network type is configured Answer: C QUESTION 27

Refer to the exhibit. What action establishes the OSPF neighbor relationship without forming an adjacency? A. modify priority B. modify process ID C. modify hello interval D. modify network type Answer: C 設定 OSPF 時注意兩邊 router 的介面需要相同的 hello and dead timer。

QUESTION 28

Refer to the exhibit. After the configuration is applied, the two routers fail to establish an OSPF neighbor relationship. What is the reason for the problem? A. The OSPF router IDs are mismatched. B. Router2 is using the default hello timer. C. The network statement on Router1 is misconfigured. D. The OSPF process IDs are mismatched Answer: B OSPF 的預設 hello timer 是 10 秒，而這裡 Router1 使用 ip ospf hello-interval 5 指令修改預設的 hello timer 至 5 秒，但 Router2 沒有修改，即沿用預設值 10 秒，所以導致雙方 router 的 hello timer 不相同，不能建立鄰接關係 (adjacency) 交換 routing table。

QUESTION 29 An engineer must configure an OSPF neighbor relationship between router R1 and R3. The authentication configuration has been configured and the connecting interfaces are in the same 192.168 1.0/30 subnet. What are the next two steps to complete the configuration? (Choose two.) A. configure the hello and dead timers to match on both sides B. configure the same process ID for the router OSPF process C. configure the same router ID on both routing processes D. configure the interfaces as OSPF active on both sides E. configure both interfaces with the same area ID Answer: A, E 設定 OSPF 時注意兩邊 router 的介面需要相同的 hello and dead timer，Area ID 也需要一樣。 QUESTION 30

Refer to the exhibit. The default-information originate command is configured under the R1 OSPF configuration. After testing, workstation on VLAN 20 at Site B cannot reach a DNS server on the Internet. Which action corrects the configuration issue? A. Add the default-information originate command on R2 B. Add the always keyword to the default-information originate command on R1 C. Configure the ip route 0.0.0.0 0.0.0.0 10.10.10.18 command on R1 D. Configure the ip route 0.0.0.0 0.0.0.0 10.10.10.2 command on R2 Answer: C 如果 R2 是透過 R1 發布 OSPF 的 default information-originate 指令而得到 default route 從而可以出 Internet，那麼 R1 亦都必須指向 10.10.10.18 作為 default route，才能為 R2 處理前往 Internet 的 packet。

QUESTION 31

Refer to the exhibit. If configuring a static default route on the router with the ip route 0.0.0.0 0.0.0.0 10.13.0.1 120 command, how does the router respond? A. It ignores the new static route until the existing OSPF default route is removed B. It immediately replaces the existing OSPF route in the routing table with the newly configured static route C. It starts load-balancing traffic between the two default routes D. It starts sending traffic without a specific matching entry in the routing table to Gigabit Ethernet0/1 Answer: A The above default route command has the Administrative Distance (AD) of 120, which is bigger than the AD of OSPF External route (O*E2) so it will not be pushed into the routing table until the current OSPF External route is removed. QUESTION 32

Refer to the exhibit. With which metric was the route to host 172.16.0.202 learned? A. 0 B. 110 C. 38443 D. 3184439 Answer: C 如果要傳送包封至目的地電腦 172.16.0.202，Routing table 只有 OSPF route 172.16.0.128/25 才符合。 因為 172.16.0.128/25 的情況下，這個網絡的 IP address range 是 128 256，而目的地電腦 “202” 正正在這範圍內。所以 router 會以 OSPF route 處理，而這行 route 的 metric value 是 38443。 答案 D 的 EIGRP routing path 不符合這目的地電腦的範圍，因為 172.16.0.192/29，網絡的 IP address range 是 192 199。

QUESTION 33

Refer to the exhibit. The New York router is configured with static routes pointing to the Atlanta and Washington sites. Which two tasks must be performed so that the Serial0/0/0 interfaces on the Atlanta and Washington routers can reach one another? (Choose two) A. Configure the ipv6 route 2012::/126 2023::1 command on the Washington router B. Configure the ipv6 route 2023::/126 2012::1 command on the Atlanta router. C. Configure the ipv6 route 2012::/126 s0/0/0 command on the Atlanta router D. Configure the ipv6 route 2023::/126 2012::2 command on the Atlanta router E. Configure the ipv6 route 2012::/126 2023::2 command on the Washington router Answer: D, E Reference/Explanation: 如果 New York router 已經有 static route 指向 Atlanta 和 Washington，同樣 Atlanta 和 Washington router 都需要有 static route 指向 New York router。 Atlanta 加入 static route 指向 New York router 的 S0/0/0 介面 IP (即 2012::2/126) Washington 加入 static route 指向 New York router 的 S0/0/1 介面 IP (即 2023::2/126) QUESTION 34

Refer to Exhibit. An engineer configured the New York router with static routes that point to the Atlanta and Washington sites. Which command must be configured on the Atlanta and Washington routers so that both sites are able to reach the loopback2 interface on the New York router? A. ipv6 route ::/0 Serial 0/0/1 B. ipv6 route ::/0 Serial 0/0/0 C. ipv6 route 0/0 Serial 0/0/0 D. ipv6 route ::/0 2000::2 E. ip route 0.0.0.0 0.0.0.0 Serial 0/0/0 Answer: B 首先明白 static route 格式： ipv6 route 所以只有答案 B 語法和設定正確: ipv6 route ::/0 Serial 0/0/0 答案 A 錯誤，因為在 Atlanta 和 Washington router 沒有 S0/0/1 介面作為 exit interface，只有 S0/0/0 答案 C 錯誤，因為目的地不是打 0/0，而是 ::/0 (即所有目的地) 答案 D 錯誤，因為在 Atlanta 和 Washington router，離開介面 (exit interface) 應該填 S0/0/0，不是 2000::2，因為 New York Loopback2 不是和 Atlanta 和 Washington 點對點 directly connected，對它們 (Atlanta 和 Washington) 來說 2000::2 不能成為 next hop address。 答案 E 錯誤，因為 ip route 指令係給 IPv4 用的。 QUESTION 35

Refer to Exhibit. The loopback1 interface of the Atlanta router must reach the loopback3 interface of the Washington router. Which two static host routes must be configured on the New York router? (Choose two). A. ipv6 route 2000::1/128 2012::1 B. ipv6 route 2000::3/128 2023::3 C. ipv6 route 2000::3/128 s0/0/0 D. ipv6 route 2000::1/128 2012::2 E. ipv6 route 2000::1/128 s0/0/1 Answer: A, B 這題只需在 New York router 加入 IPv6 static route，清楚留意 Atlanta 和 Washington 的介面 IP address，就知道 static route 的 next hop 是甚麼！ New York 加入 static route 指向 Atlanta router 的 S0/0/0 介面 IP (即 2012::1/126) New York 加入 static route 指向 Washington router 的 S0/0/0 介面 IP (即 2023::3/126)

QUESTION 36 Drag and drop the TCP/IP protocols from the left onto their primary transmission protocols on the right. Select and Place:

Answer:

QUESTION 37 Drag the descriptions of IP protocol transmissions from the left onto the IP traffic types on the right. Select and Place:

Answer:

QUESTION 38

Refer to the exhibit. An engineer is tasked with verify network configuration parameters on a client workstation to report back to the team lead. Drag and drop the node identifiers from the left onto the parameters on the right.

Answer: