CCNA CLI Questions — 30 Questions

Question 1

You are connected to SW1 via the console. SW1 is a Layer 2 switch. Port GigabitEthernet0/1 connects to a PC in VLAN 10, and port GigabitEthernet0/2 connects to a server in VLAN 20. Both ports are currently in VLAN 1. Configure SW1 to assign GigabitEthernet0/1 to VLAN 10 and GigabitEthernet0/2 to VLAN 20, and verify the configuration.

Accepted Answer

interface GigabitEthernet0/1
switchport mode access
switchport access vlan 10
interface GigabitEthernet0/2
switchport mode access
switchport access vlan 20
end
show vlan brief. Access ports carry traffic for a single VLAN. By assigning G0/1 to VLAN 10 and G0/2 to VLAN 20, the PC and server are placed in their respective VLANs.

Answer

interface GigabitEthernet0/1
switchport mode trunk
switchport trunk allowed vlan 10
interface GigabitEthernet0/2
switchport mode trunk
switchport trunk allowed vlan 20
end
show interfaces trunk

Answer

vlan 10
name PC_VLAN
vlan 20
name Server_VLAN
interface GigabitEthernet0/1
switchport mode access
switchport access vlan 10
interface GigabitEthernet0/2
switchport mode access
switchport access vlan 20
end
show vlan brief

Answer

interface GigabitEthernet0/1
switchport access vlan 10
interface GigabitEthernet0/2
switchport access vlan 20
end
show vlan brief

Question 2

You are connected to R1. The network administrator has partially configured IPv4 and IPv6 on the interfaces. However, PC1 (connected to R1's G0/1) cannot reach PC2 (connected to R2's G0/1). Configure R1 and R2 so that PC1 can ping PC2. Fix any addressing errors. Use IPv4 subnet 192.0.2.0/30 for the link between R1 and R2, and 198.51.100.0/24 for the PC LANs. For IPv6, use 2001:db8:1::/64 on R1's G0/1 and 2001:db8:2::/64 on R2's G0/1, with R1's G0/1 using EUI-64 and R2's G0/1 using a static address 2001:db8:2::1/64.

Accepted Answer

On R1, change the subnet mask on G0/0 from /24 to /30. On R1 G0/1, issue 'ipv6 address 2001:db8:1::/64 eui-64' and 'no shutdown'. Enable 'ipv6 unicast-routing' globally on both routers.. The issue is a subnet mask mismatch on the link between R1 and R2: R1 uses /24 (255.255.255.0) while R2 uses /30 (255.255.255.252). This prevents R1 from having a route to R2's LAN. Fix R1's G0/0 mask to /30. Additionally, R1's G0/1 IPv6 EUI-64 command is missing the interface identifier; the correct command is 'ipv6 address 2001:db8:1::/64 eui-64' but the interface must be enabled with 'no shutdown'. Also ensure IPv6 unicast-routing is enabled. The PCs have correct gateways.

Answer

On R1, change the subnet mask on G0/0 from /24 to /30. On R1 G0/1, issue 'ipv6 address 2001:db8:1::/64 eui-64' and 'no shutdown'. No need to enable IPv6 unicast-routing because it is on by default.

Answer

On R1, change the subnet mask on G0/0 from /24 to /30. On R1 G0/1, issue 'ipv6 address 2001:db8:1::/64' (without eui-64) and 'no shutdown'. Enable 'ipv6 unicast-routing' globally on both routers.

Answer

On R1, change the subnet mask on G0/0 from /24 to /30. On R1 G0/1, issue 'ipv6 address 2001:db8:1::/64 eui-64' and 'no shutdown'. Enable 'ipv6 unicast-routing' globally on both routers. Also, change the default gateway on PC1 to 2001:db8:1::1.

Question 3

You are troubleshooting a PC (PC-A) connected to switch SW1, which is connected to router R1. PC-A has an APIPA address (169.254.23.45) and cannot reach the internet (203.0.113.1). You confirm that R1 has a correctly configured DHCP pool for the 192.168.10.0/24 subnet, but the DHCP service is not enabled. The network uses VLAN 10 with subnet 192.168.10.0/24. Verify and correct the configuration on PC-A, SW1, and R1 to restore full connectivity.

Accepted Answer

Enable the DHCP service on R1 with the 'service dhcp' command.. The APIPA address (169.254.x.x) indicates that PC-A failed to obtain a DHCP lease. The correct solution is to enable the DHCP service on R1 with 'service dhcp', which is not running despite the configured pool. Option B is incorrect because setting a default gateway on PC-A with a static IP would still require a valid address in the subnet; the APIPA address cannot communicate with 192.168.10.1. Option C is wrong because the PC-A interface on SW1 is correctly assigned to VLAN 10. Option D is unnecessary since R1 is directly connected to the same subnet, so 'ip helper-address' is only used to forward DHCP broadcasts across router boundaries.

Answer

Configure a default gateway on PC-A with the IP address 192.168.10.1.

Answer

Change the VLAN on SW1's interface connected to PC-A from VLAN 10 to VLAN 1.

Answer

Add the 'ip helper-address' command on R1's interface connected to SW1.

Question 4

You are connected to a multilayer switch MLS1 via the console. Configure MLS1 so that IP phones connected to interface GigabitEthernet0/1 receive power via PoE, use VLAN 10 for data traffic, and use VLAN 20 for voice traffic, while the access port for an AP on GigabitEthernet0/2 should be placed in VLAN 30 and have PoE disabled. Verify your configuration using appropriate show commands.

Accepted Answer

interface GigabitEthernet0/1
 switchport mode access
 switchport access vlan 10
 switchport voice vlan 20
 power inline auto
!
interface GigabitEthernet0/2
 switchport mode access
 switchport access vlan 30
 power inline never. For the IP phone port (G0/1), you need to enable PoE (power inline auto) and configure the voice VLAN (switchport voice vlan 20) so that the phone uses VLAN 20 for voice and the access VLAN 10 for data. For the AP port (G0/2), you must change the access VLAN to 30 and disable PoE (power inline never) to prevent powering the AP through the switch. Verify with 'show interfaces switchport' to confirm voice VLAN and access VLAN settings, and 'show power inline' to check PoE status.

Answer

interface GigabitEthernet0/1
 switchport mode trunk
 switchport trunk allowed vlan 10,20
 power inline auto
!
interface GigabitEthernet0/2
 switchport mode access
 switchport access vlan 30
 power inline never

Answer

interface GigabitEthernet0/1
 switchport mode access
 switchport access vlan 20
 switchport voice vlan 10
 power inline auto
!
interface GigabitEthernet0/2
 switchport mode access
 switchport access vlan 30
 power inline never

Answer

interface GigabitEthernet0/1
 switchport mode access
 switchport access vlan 10
 switchport voice vlan 20
 power inline never
!
interface GigabitEthernet0/2
 switchport mode access
 switchport access vlan 30
 power inline auto

Question 5

You are connected to R1. Configure IPv4 and IPv6 addressing on R1's interfaces and verify reachability to R2. The current configuration has a wrong subnet mask on G0/0, missing default gateway for IPv4, and R1's IPv6 address is configured using EUI-64 while R2 uses a static IPv6 address. Fix these issues so that R1 can ping both R2's IPv4 and IPv6 addresses.

Accepted Answer

Change R1 G0/0 subnet mask to /30, add a default route via 192.0.2.2, and configure a static IPv6 address 2001:db8:1::1/64 on G0/0.. The problem had three issues: (1) R1's G0/0 subnet mask was /24 (255.255.255.0) but R2's G0/0 was /30 (255.255.255.252), causing an IP subnet mismatch. (2) R1 lacked a default gateway for IPv4; the static route pointed to 192.0.2.254 which is not reachable. (3) R1's IPv6 EUI-64 configuration on G0/0 generates an interface ID from the MAC, but R2 expects a static address 2001:db8:1::2/64, so R1 must use a static IPv6 address on the same subnet. The fix: change R1's G0/0 mask to /30, add a default route via R2's G0/0 IP (192.0.2.2), and configure a static IPv6 address (e.g., 2001:db8:1::1/64) on R1's G0/0.

Answer

Change R1 G0/0 subnet mask to /30, add a default route via 192.0.2.254, and keep the EUI-64 IPv6 address on G0/0.

Answer

Change R1 G0/0 subnet mask to /24, add a default route via 192.0.2.2, and configure a static IPv6 address 2001:db8:1::1/64 on G0/0.

Answer

Change R1 G0/0 subnet mask to /30, add a default route via 192.0.2.2, and keep the EUI-64 IPv6 address on G0/0.

Question 6

You are connected to SW1 via the console. The network uses Rapid-PVST+ and you need to ensure that SW1 becomes the root bridge for VLAN 10 and VLAN 20. Additionally, configure PortFast and BPDU Guard on interface GigabitEthernet0/1, which connects to a workstation. After configuration, the workstation is moved and the port goes err-disabled. Diagnose the cause and recover the port without reloading the switch.

Accepted Answer

Configure spanning-tree vlan 10 priority 4096 and spanning-tree vlan 20 priority 4096. Then on interface GigabitEthernet0/1, configure spanning-tree portfast and spanning-tree bpduguard enable. After removing the BPDU source, use 'shutdown' and 'no shutdown' to recover the port.. SW1 is currently the root for VLAN 10 but not for VLAN 20. To become root for both VLANs, set the spanning-tree priority to a lower value (e.g., 4096) for each VLAN. The port Gi0/1 went err-disabled because it received a BPDU, which is unexpected on a PortFast edge port with BPDU Guard enabled. To recover, first identify and remove the BPDU source (likely another switch connected to that port), then use 'shutdown' followed by 'no shutdown' on the interface to bring it back up.

Answer

Configure spanning-tree vlan 10,20 root primary and spanning-tree portfast on Gi0/1; then use 'errdisable recovery cause bpduguard' to automatically recover the port.

Answer

Configure spanning-tree vlan 10,20 priority 0 and spanning-tree bpduguard enable on Gi0/1; then use 'no spanning-tree bpduguard' to recover the port.

Answer

Configure spanning-tree vlan 10,20 priority 4096 and spanning-tree portfast on Gi0/1; then use 'clear spanning-tree detected-protocols' to recover the port.

Question 7

You are connected to R1. Configure DHCP services so that hosts on VLAN 10 (192.168.10.0/24) can obtain IP addresses from R1. Additionally, configure the switch SW1 to prevent rogue DHCP server attacks on that VLAN. The current configuration has a misconfigured helper-address and an excluded-address range that is too broad.

Accepted Answer

On R1, change the helper-address to 192.168.10.1 and the excluded-address range to 192.168.10.1 192.168.10.10. On SW1, enable DHCP snooping globally and for VLAN 10, and set interface G0/1 as trusted.. The helper-address on R1's subinterface points to 10.0.0.2 instead of the DHCP server's IP (R1 itself, which is the server). The excluded-address range excludes all addresses in the subnet, preventing any host from getting an IP. The fix: change helper-address to 192.168.10.1 (loopback or interface IP of R1), and narrow the excluded range to the first 10 addresses (or just the gateway). On SW1, enable DHCP snooping globally and for VLAN 10, and mark the port facing R1 (G0/1) as trusted; other ports should be untrusted to block rogue servers.

Answer

On R1, change the helper-address to 192.168.10.255 and the excluded-address range to 192.168.10.1 192.168.10.10. On SW1, enable DHCP snooping globally and for VLAN 10, and set all ports as trusted.

Answer

On R1, change the helper-address to 192.168.10.1 and the excluded-address range to 192.168.10.1 192.168.10.254. On SW1, enable DHCP snooping globally and for VLAN 10, and set interface G0/1 as untrusted.

Answer

On R1, change the helper-address to 192.168.10.1 and the excluded-address range to 192.168.10.1 192.168.10.10. On SW1, enable DHCP snooping globally and for VLAN 10, and set interface G0/1 as untrusted.

Question 8

You are connected to R1. The network has two routers (R1, R2) and a switch (SW1) in between. R1's G0/0 connects to SW1 (192.168.1.1/24), SW1 connects to R2's G0/0 (192.168.1.2/24). R2 has a loopback (Lo0: 203.0.113.1/32) used as a management address. Configure an extended ACL on R1 so that only SSH (TCP/22) traffic from the 10.0.0.0/24 network is permitted to reach R2's loopback; all other traffic to that loopback must be denied. Then apply the ACL in the correct direction on the correct interface.

Accepted Answer

access-list 100 permit tcp 10.0.0.0 0.0.0.255 host 203.0.113.1 eq 22
access-list 100 deny ip any host 203.0.113.1
interface GigabitEthernet0/1
 ip access-group 100 in. The current configuration has no ACL restricting traffic to R2's loopback. The candidate must create an extended ACL that permits TCP from 10.0.0.0/24 to host 203.0.113.1 eq 22, then deny all other IP traffic to that host. The ACL must be applied inbound on R1's G0/1 (facing the 10.0.0.0/24 network) to filter traffic before it enters R1. Applying outbound on G0/0 would also work, but inbound on G0/1 is more efficient and typical. The implicit deny at the end of the ACL blocks all other traffic to the loopback.

Answer

access-list 100 permit tcp 10.0.0.0 0.0.0.255 host 203.0.113.1 eq 22
access-list 100 deny ip any host 203.0.113.1
interface GigabitEthernet0/0
 ip access-group 100 out

Answer

access-list 100 permit tcp 10.0.0.0 0.0.0.255 host 203.0.113.1 eq 22
interface GigabitEthernet0/1
 ip access-group 100 in

Answer

access-list 100 permit tcp 10.0.0.0 0.0.0.255 host 203.0.113.1 eq 22
access-list 100 deny ip any any
interface GigabitEthernet0/1
 ip access-group 100 in

Question 9

You are connected to a Multilayer Switch MLS1. Configure the switch so that interface GigabitEthernet1/0/1 is an access port for VLAN 10, with voice VLAN 110 for an IP phone, and enable PoE. Additionally, interface GigabitEthernet1/0/2 must be an access port for VLAN 20 to connect an AP. Verify the configuration using 'show interfaces switchport' and 'show power inline'.

Accepted Answer

interface GigabitEthernet1/0/1
 switchport mode access
 switchport access vlan 10
 switchport voice vlan 110
 power inline auto
interface GigabitEthernet1/0/2
 switchport mode access
 switchport access vlan 20. It configures Gi1/0/1 as an access port in VLAN 10 with voice VLAN 110 and PoE enabled, and Gi1/0/2 as an access port in VLAN 20. Option B is wrong because it uses 'switchport mode trunk' instead of 'switchport mode access'. For a voice VLAN, the port should be an access port, not a trunk. Option C is wrong because it disables PoE with 'power inline never', but the IP phone requires power. Option D is wrong because it assigns the access VLAN as 110 and voice VLAN as 10, reversing the intended roles. Verify with 'show interfaces switchport' and 'show power inline'.

Answer

interface GigabitEthernet1/0/1
 switchport mode trunk
 switchport trunk allowed vlan 10,110
 power inline auto
interface GigabitEthernet1/0/2
 switchport mode access
 switchport access vlan 20

Answer

interface GigabitEthernet1/0/1
 switchport mode access
 switchport access vlan 10
 switchport voice vlan 110
 power inline never
interface GigabitEthernet1/0/2
 switchport mode access
 switchport access vlan 20

Answer

interface GigabitEthernet1/0/1
 switchport mode access
 switchport access vlan 110
 switchport voice vlan 10
 power inline auto
interface GigabitEthernet1/0/2
 switchport mode access
 switchport access vlan 20

Question 10

You are connected to R1, a multilayer switch acting as the STP root bridge. Configure Root Guard on the designated port toward R2 (G0/1), Loop Guard on the uplink port G0/2, and BPDU Guard on PortFast-enabled access port G0/3. After configuration, a superior BPDU is received on G0/1, causing it to be blocked by Root Guard; later, an unauthorized BPDU on G0/3 triggers err-disable. Troubleshoot and verify the expected port states.

Accepted Answer

G0/1 is in blocking state (Root Guard), G0/2 is in forwarding state (Loop Guard), G0/3 is in err-disable state (BPDU Guard).. The root guard on G0/1 correctly blocked the port when a superior BPDU was received, preventing an unauthorized root bridge. Loop Guard was applied specifically to the uplink port G0/2 to prevent forwarding loops in case of uni-directional link failure. BPDU Guard on G0/3 placed the port into err-disable state upon receiving an unexpected BPDU, which protects the PortFast edge port. To restore G0/3, you must manually shut/no shut the interface after removing the offending device.

Answer

G0/1 is in forwarding state (Root Guard), G0/2 is in blocking state (Loop Guard), G0/3 is in err-disable state (BPDU Guard).

Answer

G0/1 is in err-disable state (Root Guard), G0/2 is in forwarding state (Loop Guard), G0/3 is in blocking state (BPDU Guard).

Answer

G0/1 is in blocking state (Root Guard), G0/2 is in loop-inconsistent state (Loop Guard), G0/3 is in err-disable state (BPDU Guard).

Question 11

You are connected to SW1. An EtherChannel between SW1 and SW2 using LACP must be established on interfaces GigabitEthernet0/1 and GigabitEthernet0/2. Currently, the channel is not forming. Inspect the provided configuration and output, then apply the necessary commands on SW1 to resolve the issue and bring up the Port-Channel interface.

Accepted Answer

Configure both interfaces with speed 1000, duplex full, and switchport access vlan 1.. The EtherChannel failed because the two member interfaces on SW1 have mismatched speed (Gi0/1: 1000 Mbps, Gi0/2: 100 Mbps) and duplex (Gi0/1: full, Gi0/2: half), and their native VLANs differ (Gi0/1: VLAN 1, Gi0/2: VLAN 10). LACP requires all bundled ports to have identical speed, duplex, and VLAN configuration. To fix, on SW1 configure both interfaces with consistent settings: set speed 1000, duplex full, and switchport access vlan 1 (or a common trunk native VLAN). Also ensure both sides use the same LACP mode (both active or active/passive); here SW2's Gi0/2 is passive, which is acceptable with SW1's active, so the primary issue is the mismatched physical and VLAN parameters. After correction, the channel will form.

Answer

Change the LACP mode on SW1's Gi0/2 from active to passive.

Answer

Configure both interfaces with speed 100, duplex half, and switchport access vlan 10.

Answer

Remove the switchport access vlan command from both interfaces and configure them as trunk ports with native vlan 1.

Question 12

You are connected to R1 via the console. R1 is the DHCP server for the 192.168.50.0/24 LAN. Configure DHCP on R1 to assign addresses from 192.168.50.10 to 192.168.50.200, with default gateway 192.168.50.1 and DNS server 8.8.8.8. Also, configure R1 to act as a DHCP relay agent for the 10.0.0.0/30 link to reach a remote DHCP server at 203.0.113.10. Then, troubleshoot and fix a misconfiguration that causes clients on VLAN 50 to not receive IP addresses.

Accepted Answer

[CORRECT] The DHCP pool is misconfigured: the excluded-address range covers most of the pool (192.168.50.1 through 192.168.50.200), but leaves 192.168.50.201-254 assignable, violating the requirement. The correct configuration should exclude 192.168.50.1-9 (gateway) and 192.168.50.201-254 (upper end). The 'ip helper-address' on GigabitEthernet0/0 is unnecessary because R1 itself is the DHCP server for that subnet; it should be removed. The relay agent configuration is missing on the interface facing the remote DHCP server—'ip helper-address 203.0.113.10' should be added to GigabitEthernet0/1.. The DHCP pool is misconfigured: the excluded-address range of 192.168.50.1 through 192.168.50.200 covers most of the pool, but leaves addresses 192.168.50.201 to 192.168.50.254 assignable, which violates the requirement to assign addresses only from 192.168.50.10 to 192.168.50.200. To meet the requirement, you must exclude both the lower range (192.168.50.1 to 192.168.50.9, reserving the gateway) and the upper range (192.168.50.201 to 192.168.50.254). Additionally, the 'ip helper-address' on GigabitEthernet0/0 is unnecessary because R1 itself is the DHCP server for that subnet; it should be removed. The relay agent configuration is missing on the interface facing the remote DHCP server—'ip helper-address 203.0.113.10' should be added to GigabitEthernet0/1 so that broadcasts from the 10.0.0.0/30 subnet are forwarded.

Answer

The DHCP pool is misconfigured: the excluded-address range should be 192.168.50.1 192.168.50.9, but the helper-address on GigabitEthernet0/0 is correct because it forwards DHCP requests to the remote server. The relay agent configuration is missing on GigabitEthernet0/1.

Answer

The DHCP pool is correctly configured with excluded-address 192.168.50.1 192.168.50.9. The issue is that the 'ip helper-address' on GigabitEthernet0/1 is missing; it should be added to forward requests to the remote server. Additionally, the 'ip helper-address' on GigabitEthernet0/0 is correct because it forwards requests from VLAN 50 to the remote server.

Answer

The DHCP pool is misconfigured: the excluded-address range should be 192.168.50.1 192.168.50.9. The 'ip helper-address' on GigabitEthernet0/0 should be removed. The relay agent configuration is correct because 'ip helper-address 203.0.113.10' is already configured on GigabitEthernet0/1.

Question 13

You are connected to R1 via the console. R1 has two directly connected interfaces: G0/0 to R2 (IPv4 only) and G0/1 to a LAN switch (dual stack). Your task: configure IPv4 and IPv6 default routes on R1 pointing to R2 (next-hop 10.0.0.2 and 2001:db8:1::2). Also configure a floating static route to 192.0.2.0/24 via R2 with an administrative distance of 10 (so it is used only if the directly connected route fails). The current running-config shows an incorrect static route that causes recursive routing failure. Identify and fix the issue.

Accepted Answer

Remove the incorrect static route 192.0.2.0 255.255.255.0 10.0.0.1 and add ip route 192.0.2.0 255.255.255.0 10.0.0.2 10. The static route to 192.0.2.0/24 uses next-hop 10.0.0.1, which is R1's own interface IP, not R2's. This causes recursive routing failure because the router tries to reach itself. The correct next-hop should be 10.0.0.2 (R2's G0/0 IP). Additionally, the floating static route must have a higher AD (10) so it is less preferred than the directly connected route (AD 0). Remove the incorrect route and add the correct floating static route with AD 10.

Answer

Remove the incorrect static route 192.0.2.0 255.255.255.0 10.0.0.1 and add ip route 192.0.2.0 255.255.255.0 10.0.0.2 1

Answer

Keep the existing static route and add ip route 192.0.2.0 255.255.255.0 10.0.0.2 10

Answer

Remove the incorrect static route 192.0.2.0 255.255.255.0 10.0.0.1 and add ip route 192.0.2.0 255.255.255.0 g0/0

Question 14

You are connected to R1 via the console. R1 is a router that needs to provide DHCP services for hosts on VLAN 10 (192.168.10.0/24) and VLAN 20 (192.168.20.0/24). The DHCP server is located on VLAN 10 at 192.168.10.100, but hosts on VLAN 20 cannot reach it directly. Configure R1 to forward DHCP broadcasts from VLAN 20 to the DHCP server.

Accepted Answer

interface GigabitEthernet0/0.20
 encapsulation dot1Q 20
 ip helper-address 192.168.10.100. The ip helper-address command enables the router to forward UDP broadcasts (including DHCP) to a specific server. Placing it on the VLAN 20 subinterface ensures that DHCP requests from VLAN 20 are unicast to the server on VLAN 10.

Answer

interface GigabitEthernet0/0.10
 encapsulation dot1Q 10
 ip helper-address 192.168.10.100

Answer

interface GigabitEthernet0/0.20
 encapsulation dot1Q 20
 ip dhcp relay information option

Answer

ip dhcp pool VLAN20
 network 192.168.20.0 255.255.255.0
 default-router 192.168.20.1

Question 15

You are connected to R1, a router that serves as the DNS resolver for the local network 192.168.10.0/24. Users report that they cannot resolve the hostname 'webserver.internal' to its IP address (192.168.10.50), and reverse DNS lookups for that IP return a different name. Additionally, some queries to an external domain 'example.com' time out. Diagnose and fix the DNS configuration on R1 using nslookup and dig commands where applicable, ensuring proper forward and reverse resolution for internal hosts and reachability to external DNS servers.

Accepted Answer

Remove the unreachable DNS server 192.0.2.53, add an A record for webserver.internal (192.168.10.50), and correct the PTR record for 192.168.10.50 to point to webserver.internal.. The DNS server 192.0.2.53 is unreachable, causing timeouts for external queries. The primary DNS server 203.0.113.53 returns NXDOMAIN for 'webserver.internal' because no A record exists for that hostname in the internal zone. Additionally, the PTR record for 192.168.10.50 incorrectly points to 'mail.internal' instead of 'webserver.internal'. To fix, first remove the unreachable DNS server with 'no ip name-server 192.0.2.53' or replace it with a reachable one. Then, on the DNS server (or via static host entries on R1), add an A record for webserver.internal (192.168.10.50) and correct the PTR record to point to webserver.internal. Optionally, configure 'ip host webserver.internal 192.168.10.50' on R1 for local resolution.

Answer

Add an A record for webserver.internal (192.168.10.50) and correct the PTR record for 192.168.10.50 to point to webserver.internal, but leave the unreachable DNS server 192.0.2.53 in the configuration.

Answer

Remove the unreachable DNS server 192.0.2.53 and add an A record for webserver.internal (192.168.10.50), but do not correct the PTR record for 192.168.10.50.

Answer

Replace the unreachable DNS server 192.0.2.53 with a reachable one, and correct the PTR record for 192.168.10.50 to point to webserver.internal, but do not add an A record for webserver.internal.

Question 16

You are troubleshooting connectivity for a wireless client connected to the home network shown below. The client has obtained an APIPA address (169.254.x.x), indicating DHCP failure. Verify the DHCP server configuration on R1 and correct the issue so that the client receives a valid IP address from the 192.168.1.0/24 subnet.

Accepted Answer

Enable the DHCP service globally using the 'service dhcp' command on R1.. The client obtained an APIPA address (169.254.x.x) because DHCP was not assigning addresses. The DHCP pool is correctly configured, but the global DHCP service must be enabled with the 'service dhcp' command on R1. The excluded-address range (192.168.1.1–192.168.1.10) uses only a small fraction of the /24 subnet, so it is not the issue. Enabling 'service dhcp' allows the router to process DHCP requests and assign addresses from the pool.

Answer

Remove the 'ip dhcp excluded-address 192.168.1.1 192.168.1.10' command because it excludes too many addresses.

Answer

Change the DHCP pool network to 192.168.1.0/24 and add the default-router 192.168.1.1 command.

Answer

Configure the 'ip helper-address' command on the client's VLAN interface to forward DHCP requests to the server.

Question 17

You are connected to R1. Configure NTP client so that R1 synchronizes with the NTP server at 198.51.100.10, using its Loopback0 (10.0.0.1/32) as the source interface. Also configure syslog to send messages of severity 5 (notifications) and above to 192.0.2.20. The current configuration shows a misconfigured NTP server address and an incorrect logging trap level. Verify with 'show ntp status' (stratum should not be 16) and 'show logging'.

Accepted Answer

ntp server 198.51.100.10 source Loopback0
logging trap notifications. The misconfigured NTP server address (203.0.113.5) and the debug-level logging trap (7) must be corrected to meet requirements. The correct commands are 'ntp server 198.51.100.10 source Loopback0' to use the specified server and Loopback0 as source, and 'logging trap notifications' (severity 5) to send only notifications and more severe messages. Option B is wrong because 'logging trap 4' sets the trap level to warning, which would not forward notifications. Option C misses the source interface, and Option D uses the wrong NTP server and an overly verbose trap level.

Answer

ntp server 198.51.100.10 source Loopback0
logging trap 4

Answer

ntp server 198.51.100.10
logging trap notifications

Answer

ntp server 203.0.113.5 source Loopback0
logging trap 7

Question 18

You are connected to SW1 via the console. The network has three switches connected in a triangle: SW1 (G0/1 to SW2 G0/1), SW1 (G0/2 to SW3 G0/1), and SW2 (G0/2 to SW3 G0/2). SW1 is the root bridge. A PC is connected to SW3's G0/3 port, which should be an edge port. However, the PC has been sending BPDUs, causing the port to go err-disabled. Configure SW3 to prevent this in the future: enable PortFast and BPDU Guard on G0/3. Then, verify that the port recovers from err-disabled state and that a specific blocked port on SW2 is identified. Use the provided show output to determine the current state and necessary commands.

Accepted Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 shutdown
 no shutdown. The PC connected to SW3's G0/3 was sending BPDUs, causing the port to go err-disabled due to BPDU Guard. To prevent this, enable PortFast and BPDU Guard on that interface. First, move to interface configuration mode for G0/3, then issue 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. After configuration, the port will remain err-disabled until manually recovered by issuing 'shutdown' followed by 'no shutdown'. The blocked port on SW2 is G0/2, as shown by the 'Altn BLK' role/status in its spanning-tree output.

Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 no shutdown

Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 end
 copy running-config startup-config

Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 shutdown

Question 19

You are connected to R1. Configure HSRP on R1 and R2 so that R1 is the active gateway for VLAN 100 with a virtual IP of 192.0.2.254. R1 should preempt and track its G0/1 interface to decrement priority by 20 if it goes down. Currently, both routers show active for the group, and the virtual IP is incorrectly set. Troubleshoot and fix the configuration on R1 only.

Accepted Answer

Change the virtual IP to 192.0.2.254 and set priority to 110.. The issue is that both routers are active because the virtual IP on R1 was 192.168.100.254, which is not in the same subnet as the interface IP (192.0.2.1/24), so HSRP couldn't form a common group. Changing the virtual IP to 192.0.2.254 fixes the subnet mismatch. Additionally, setting R1's priority to 110 ensures it becomes the active router because it has preempt configured, and the higher priority overrides R2's default 100. The track command remains correct as it reduces priority if G0/1 fails.

Answer

Change the virtual IP to 192.0.2.254 and remove the track command.

Answer

Change the virtual IP to 192.0.2.254 and configure preempt on R2.

Answer

Change the virtual IP to 192.0.2.254 and set priority to 100.

Question 20

You are connected to a multilayer switch MLS1. Configure Root Guard on the designated port facing another switch SW2 to prevent it from becoming root, configure Loop Guard on the uplink port to the core, and configure BPDU Guard on a PortFast-enabled access port. After configuration, a superior BPDU arrives on the designated port—confirm it is blocked by Root Guard. Then, simulate a BPDU on the access port to verify it goes err-disabled due to BPDU Guard.

Accepted Answer

Root Guard on Gi0/2, Loop Guard on Gi0/1, BPDU Guard on Gi0/0. First, Root Guard was applied on Gi0/2 (the designated port) with 'spanning-tree guard root' to prevent SW2 from becoming root. Second, Loop Guard was applied on the uplink Gi0/1 with 'spanning-tree guard loop' to protect against unidirectional links. Third, BPDU Guard was applied on the PortFast-enabled access port Gi0/0 with 'spanning-tree bpduguard enable'. When a superior BPDU arrives on Gi0/2, Root Guard transitions it to a root-inconsistent (blocked) state. If a BPDU is received on Gi0/0, BPDU Guard err-disables the port. Verification shows the blocked state on Gi0/2 and err-disabled on Gi0/0.

Answer

Root Guard on Gi0/1, Loop Guard on Gi0/2, BPDU Guard on Gi0/0

Answer

Root Guard on Gi0/0, Loop Guard on Gi0/1, BPDU Guard on Gi0/2

Answer

Root Guard on Gi0/2, Loop Guard on Gi0/0, BPDU Guard on Gi0/1