CCNA IP Routing Practice Test 21 — 15 Questions

Question 1

Drag and drop the following steps into the correct order to describe the router's routing table lookup process for a destination IP address, including the best-path selection logic (longest prefix match, then administrative distance, then metric) and the final forwarding decision.

Accepted Answer

1. Perform longest prefix match on destination IP address
2. If multiple routes match, compare administrative distance
3. If AD is equal, compare metric
4. Forward packet using the best route. The router applies longest prefix match first, then administrative distance, then metric, in that order, to select the best path and forward the packet.

Answer

1. Compare administrative distance of all routes
2. Compare metric of routes with lowest AD
3. Perform longest prefix match on remaining routes
4. Forward packet using the best route

Answer

1. Compare metric of all routes
2. Compare administrative distance of routes with lowest metric
3. Perform longest prefix match on remaining routes
4. Forward packet using the best route

Answer

1. Perform longest prefix match on destination IP address
2. If multiple routes match, compare metric
3. If metric is equal, compare administrative distance
4. Forward packet using the best route

Question 2

Drag and drop the following steps into the correct order to describe how a router selects the best path and forwards a packet, using the routing table lookup process from destination IP to forwarding decision.

Accepted Answer

Step 1: Examine the destination IP address of the packet.
Step 2: Perform a longest prefix match on the routing table.
Step 3: Determine the next-hop IP address and outgoing interface.
Step 4: Forward the packet to the next hop.. The router first identifies the destination IP, then finds the best matching route using longest prefix match, and forwards to the next hop.

Answer

Step 1: Perform a longest prefix match on the routing table.
Step 2: Examine the destination IP address of the packet.
Step 3: Determine the next-hop IP address and outgoing interface.
Step 4: Forward the packet to the next hop.

Answer

Step 1: Examine the destination IP address of the packet.
Step 2: Determine the next-hop IP address and outgoing interface.
Step 3: Perform a longest prefix match on the routing table.
Step 4: Forward the packet to the next hop.

Answer

Step 1: Determine the next-hop IP address and outgoing interface.
Step 2: Examine the destination IP address of the packet.
Step 3: Perform a longest prefix match on the routing table.
Step 4: Forward the packet to the next hop.

Question 3

Drag and drop the following steps into the correct order for the router's routing table lookup process when forwarding a packet to a destination IP address, including the best-path selection logic.

Accepted Answer

1. Match the destination IP address with the longest prefix in the routing table. 2. If multiple routes match, select the route with the lowest administrative distance. 3. If still multiple routes, select the route with the lowest metric.. The routing table lookup first matches the destination with the longest prefix, then applies tie-breakers: lowest administrative distance, then lowest metric, to determine the best path for forwarding.

Answer

1. Match the destination IP address with the longest prefix in the routing table. 2. If multiple routes match, select the route with the lowest metric. 3. If still multiple routes, select the route with the lowest administrative distance.

Answer

1. Match the destination IP address with any prefix in the routing table (first match). 2. If multiple routes match, select the route with the lowest administrative distance. 3. If still multiple routes, select the route with the lowest metric.

Answer

1. Match the destination IP address with the longest prefix in the routing table. 2. If multiple routes match, select the route with the lowest metric. 3. If still multiple routes, select the route with the highest administrative distance.

Question 4

Drag and drop the following steps into the correct order to describe the router's routing table lookup process for a destination IP address, including best-path selection using longest prefix match, administrative distance, and metric.

Accepted Answer

1. Perform longest prefix match on the destination IP address against all routes in the routing table.
2. If multiple routes match, compare administrative distances; choose the route with the lowest AD.
3. If multiple routes have the same AD, compare metrics; choose the route with the lowest metric.
4. Forward the packet using the selected route.. The order follows the router's decision process: longest prefix match first, then administrative distance, then metric, leading to the forwarding decision.

Answer

1. Compare administrative distances of all routes; choose the route with the lowest AD.
2. Perform longest prefix match on the destination IP address against the remaining routes.
3. If multiple routes have the same AD, compare metrics; choose the route with the lowest metric.
4. Forward the packet using the selected route.

Answer

1. Perform longest prefix match on the destination IP address against all routes in the routing table.
2. If multiple routes match, compare metrics; choose the route with the lowest metric.
3. If multiple routes have the same metric, compare administrative distances; choose the route with the lowest AD.
4. Forward the packet using the selected route.

Answer

1. Compare metrics of all routes; choose the route with the lowest metric.
2. Perform longest prefix match on the destination IP address against the remaining routes.
3. If multiple routes have the same metric, compare administrative distances; choose the route with the lowest AD.
4. Forward the packet using the selected route.

Question 5

Drag and drop the following steps into the correct order to describe the router's routing table lookup process from receiving a packet with a destination IP address to making the forwarding decision, including best-path selection criteria.

Accepted Answer

Packet arrival, longest prefix match, tie-breaking using administrative distance and metric, forwarding decision. The process starts with packet arrival, then longest prefix match, followed by tie-breaking using administrative distance and metric, culminating in forwarding.

Answer

Packet arrival, tie-breaking using administrative distance and metric, longest prefix match, forwarding decision

Answer

Packet arrival, longest prefix match, forwarding decision, tie-breaking using administrative distance and metric

Answer

Packet arrival, tie-breaking using administrative distance and metric, forwarding decision, longest prefix match

Question 6

You are connected to R1 via console. The network has a primary link to the ISP via R2 and a backup link via R3. Configure IPv4 and IPv6 floating static default routes on R1 so that the primary path goes through R2 (AD 1) and the backup through R3 (AD 10). Additionally, configure a static route on R1 for the internal LAN 192.168.10.0/24 via R2 (AD 1). The current configuration includes a static default route ip route 0.0.0.0 0.0.0.0 10.0.0.3, which causes a recursive routing failure because 10.0.0.3 is not a valid next-hop address. Identify and fix the issue, then apply the floating static routes.

Accepted Answer

Remove the existing incorrect IPv4 static default route and reconfigure the primary IPv4 default route with the correct next-hop address (10.0.0.2) and AD 1. Add the backup IPv4 default route via 10.0.0.6 with AD 10. Then add IPv6 static default routes: ipv6 route ::/0 2001:DB8:1:1::2 1 and ipv6 route ::/0 2001:DB8:2:1::2 10. Also add the static route for 192.168.10.0/24 via 10.0.0.2 with AD 1.. The IPv4 default route currently uses next-hop 10.0.0.3, which is not a valid address on any directly connected interface, causing a recursive lookup failure. Option A fixes this by removing the incorrect route and correctly adding the primary (10.0.0.2 with AD 1) and backup (10.0.0.6 with AD 10) default routes, fulfilling the floating static requirement. It also adds both IPv6 floating default routes and the LAN static route. Option B is wrong because adding a route to 10.0.0.0/30 via R3 does not fix the next-hop 10.0.0.3 failure for the default route. Option C incorrectly reverses the administrative distances, making the backup path the primary. Option D erroneously uses an exit interface instead of the correct next-hop IP, which is not suitable for multi-access or point-to-point networks without additional configuration and does not resolve the original misconfigured next-hop.

Answer

Add a static route to 10.0.0.0/30 via the backup link to R3, then the default route to 10.0.0.2 will work. Then configure IPv6 default routes with AD 1 and 10 as described.

Answer

Change the administrative distance of the IPv4 default route to 10 and the backup to 1, so the backup becomes primary. Then configure IPv6 default routes with AD 10 and 1 respectively.

Answer

Remove the existing IPv4 static default route and configure it with the next-hop as the exit interface (e.g., GigabitEthernet0/0) instead of the IP address. Then add IPv6 default routes using the exit interface as well.

Question 7

You are connected to R1. Configure IPv4 and IPv6 static routes, default routes, and floating static routes so that R1 can reach the Internet via R2 (IPv4 and IPv6). The primary route to the Internet should use next-hop 203.0.113.2 (IPv4) and 2001:db8:203:0:113::2 (IPv6). A backup floating static route with administrative distance 200 must exist for IPv4 only, using next-hop 198.51.100.2. Ensure the default routes are correctly configured and troubleshoot any recursive routing failure. Note: R1 currently has an incorrect IPv6 default route pointing to 2001:db8:198:51:100::2 that must be removed.

Accepted Answer

Remove the incorrect IPv6 default route: no ipv6 route ::/0 2001:db8:198:51:100::2; configure the primary default route: ip route 0.0.0.0 0.0.0.0 203.0.113.2; the floating route is already configured with AD 200; add IPv6 default route: ipv6 route ::/0 2001:db8:203:0:113::2. The IPv4 floating route is already correctly pre-configured with AD 200 to serve as a backup. To meet the requirements, you must add the primary IPv4 default route with default AD 1, remove the existing incorrect IPv6 default route, and add the correct IPv6 default route. Option A correctly identifies these steps, while other options either omit the removal, assign a wrong AD to the primary route, or neglect IPv6 entirely.

Answer

Configure the primary default route: ip route 0.0.0.0 0.0.0.0 203.0.113.2; change the floating route AD to 1; add IPv6 default route: ipv6 route ::/0 2001:db8:203:0:113::2

Answer

Configure the primary default route: ip route 0.0.0.0 0.0.0.0 203.0.113.2 200; the floating route is already configured with AD 200; add IPv6 default route: ipv6 route ::/0 2001:db8:203:0:113::2

Answer

Configure the primary default route: ip route 0.0.0.0 0.0.0.0 203.0.113.2; the floating route is already configured with AD 200; no IPv6 route is needed because IPv6 is not required.

Question 8

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 9

You are connected to R1. The network consists of three routers: R1, R2, and R3. R1 must reach the loopback network 203.0.113.0/24 on R3 via two paths: a primary static route through R2's G0/0 (192.0.2.2) and a floating static route through R2's G0/1 (198.51.100.2) with an administrative distance of 150. Additionally, R1 already has a default route pointing to 192.0.2.2. Configure the two static routes to 203.0.113.0/24 on R1 as described. The default route does not need to be changed. Verify that the primary route is active and the floating route is used only if the primary fails.

Accepted Answer

Configure ip route 203.0.113.0 255.255.255.0 192.0.2.2 and ip route 203.0.113.0 255.255.255.0 198.51.100.2 150. The default route is already configured. No further changes needed.. It correctly configures the primary static route to 203.0.113.0/24 via 192.0.2.2 (default AD 1) and the floating static route via 198.51.100.2 with AD 150, ensuring the primary route is preferred. The default route to 192.0.2.2 is already configured and does not need modification. Options B, C, and D are incorrect: B wrongly adds a higher AD to the default route, C inverts the ADs on the two routes, and D omits the required AD on the floating route, causing both routes to have equal AD and potential load balancing or conflict.

Answer

Configure ip route 203.0.113.0 255.255.255.0 192.0.2.2 and ip route 203.0.113.0 255.255.255.0 198.51.100.2 150. Also, remove the existing default route and re-add it with a higher administrative distance.

Answer

Configure ip route 203.0.113.0 255.255.255.0 192.0.2.2 150 and ip route 203.0.113.0 255.255.255.0 198.51.100.2. The default route is already configured.

Answer

Configure ip route 203.0.113.0 255.255.255.0 192.0.2.2 and ip route 203.0.113.0 255.255.255.0 198.51.100.2. The default route is already configured. No administrative distance is needed because the router will automatically prefer the route with the lower metric.

Question 10

You are connected to a multilayer switch MLS1. Configure a static default route for IPv4 that points to next-hop 192.0.2.2, but also configure a floating static default route with an administrative distance of 10 that uses next-hop 198.51.100.2. Additionally, configure a static host route for IPv6 host 2001:db8:1::10/128 via next-hop 2001:db8:1::1. The current configuration has a recursive routing failure for the IPv4 default route because the next-hop 192.0.2.2 is not reachable; you must first fix that by adding a directly connected static route. Ensure the floating route becomes active only when the primary route fails.

Accepted Answer

ip route 0.0.0.0 0.0.0.0 192.0.2.2
ip route 0.0.0.0 0.0.0.0 198.51.100.2 10
ip route 192.0.2.0 255.255.255.252 GigabitEthernet0/0 192.0.2.2
ipv6 route 2001:db8:1::10/128 2001:db8:1::1. The IPv4 primary default route fails because next-hop 192.0.2.2 is not directly connected and no recursive route exists to it. The floating static route with next-hop 198.51.100.2 is in the directly connected Vlan20 subnet (198.51.100.1/30), so it installs without issue. To fix the primary default route, add a directly connected static route for the network containing 192.0.2.2, e.g., ip route 192.0.2.0 255.255.255.252 GigabitEthernet0/0 192.0.2.2. The IPv6 host route is correct if next-hop 2001:db8:1::1 is reachable.

Answer

ip route 0.0.0.0 0.0.0.0 192.0.2.2
ip route 0.0.0.0 0.0.0.0 198.51.100.2 10
ip route 192.0.2.0 255.255.255.0 GigabitEthernet0/0
ipv6 route 2001:db8:1::10/128 2001:db8:1::1

Answer

ip route 0.0.0.0 0.0.0.0 192.0.2.2
ip route 0.0.0.0 0.0.0.0 198.51.100.2 10
ip route 192.0.2.2 255.255.255.255 GigabitEthernet0/0
ipv6 route 2001:db8:1::10/128 2001:db8:1::1

Answer

ip route 0.0.0.0 0.0.0.0 192.0.2.2
ip route 0.0.0.0 0.0.0.0 198.51.100.2 10
ip route 192.0.2.0 255.255.255.252 198.51.100.2
ipv6 route 2001:db8:1::10/128 2001:db8:1::1

Question 11

You are connected to R1 via console. R1 must forward traffic to the 203.0.113.0/24 and 2001:db8:1::/48 networks through R2 (10.0.0.2/30, 2001:db8:ff::2/64). The primary path must use a next-hop of 10.0.0.2 for IPv4 and 2001:db8:ff::2 for IPv6. Additionally, configure a floating static default route for IPv4 that uses R3 (192.0.2.2/30) as a backup only when the primary path fails. The current configuration has errors: the IPv4 static route points to a wrong next-hop (10.0.0.5) and the primary default route is missing, causing the floating route (AD 100) to become active instead of serving as a backup. Fix these issues so that both primary and backup routes work correctly.

Accepted Answer

Change the next-hop of the static route to 203.0.113.0/24 from 10.0.0.5 to 10.0.0.2, and add a default route 0.0.0.0/0 via 10.0.0.2 with AD 1. Keep the floating default route 0.0.0.0/0 via 192.0.2.2 with AD 100.. The IPv4 static route to 203.0.113.0/24 used a next-hop of 10.0.0.5, which is not a directly connected interface (R1's G0/0 is 10.0.0.1/30, so only .2 is valid). This caused a recursive lookup failure. The floating static default route had AD 100, but a floating route must have an AD higher than the primary route's AD (typically 1) so it is only used when the primary fails; setting AD 100 is correct for backup, but the primary default route was missing. The fix: change the next-hop for 203.0.113.0/24 to 10.0.0.2, and add a primary default route with AD 1 via 10.0.0.2. The floating route's AD of 100 is fine as backup. IPv6 route was correct.

Answer

Change the next-hop of the static route to 203.0.113.0/24 from 10.0.0.5 to 10.0.0.2, and change the administrative distance of the floating default route from 100 to 1 so it becomes the primary default route.

Answer

Change the next-hop of the static route to 203.0.113.0/24 from 10.0.0.5 to 10.0.0.2, and change the administrative distance of the floating default route from 100 to 255 so it is never used.

Answer

Change the next-hop of the static route to 203.0.113.0/24 from 10.0.0.5 to 10.0.0.2, and remove the floating default route because it is unnecessary.

Question 12

You are connected to R1. Configure static routes so that R1 can reach the IPv4 network 203.0.113.0/24 and the IPv6 network 2001:db8:acad:1::/64 via R2 (G0/0 10.0.0.2/30). Additionally, configure a floating static default route (IPv4) with an administrative distance of 200 via R2, and a fully specified IPv6 default route via R2. Then, verify that the IPv4 static route to 203.0.113.0/24 is correctly installed by checking the routing table. The current configuration has an incorrect next-hop causing recursive routing failure for the IPv4 static route.

Accepted Answer

Change the IPv4 static route next-hop from 10.0.0.1 to 10.0.0.2, change the IPv6 static route next-hop from 10.0.0.2 to 2001:db8:acad:2::2, and change the IPv6 default route to use next-hop 2001:db8:acad:2::2.. The IPv4 static route to 203.0.113.0/24 incorrectly uses next-hop 10.0.0.1 (R1's own interface) instead of 10.0.0.2 (R2), causing recursive routing failure because R1 tries to reach itself. To fix, change the next-hop to 10.0.0.2. The IPv6 static route to 2001:db8:acad:1::/64 also incorrectly uses an IPv4 next-hop; it must be a fully specified IPv6 next-hop (2001:db8:acad:2::2) or an exit interface. The IPv4 default route has AD 200 which is correct for a floating route, but it is not shown in the routing table because there is no route to the next-hop; after fixing the recursive route, the default route will appear. The IPv6 default route uses an IPv4 next-hop which is invalid; it should be a fully specified IPv6 route (e.g., ipv6 route ::/0 2001:db8:acad:2::2).

Answer

Change the IPv4 static route next-hop from 10.0.0.1 to 10.0.0.2, and change the IPv6 static route to use exit interface G0/0 instead of a next-hop.

Answer

Change the IPv4 static route next-hop from 10.0.0.1 to 10.0.0.2, and change the IPv4 default route administrative distance to 1.

Answer

Change the IPv4 static route next-hop from 10.0.0.1 to 10.0.0.2, and change the IPv6 default route to use exit interface G0/0.

Question 13

You are connected to R1 via console. R1 must reach the remote loopback 2001:db8:1::1/128 on R3 via R2 (2001:db8:0:2::2/64). Currently, IPv6 ping fails. Additionally, configure a floating static default route via R2 (198.51.100.2/30) with an appropriate AD so that it only becomes active if a dynamic default route (with default AD 1) is absent. Identify and fix the recursive routing failure, correct the next-hop, set the correct AD, and ensure the default route is present.

Accepted Answer

Change the IPv6 static route to '2001:db8:1::1/128 GigabitEthernet0/1 2001:db8:0:2::2' and set the floating default route's AD to 254.. The original IPv6 static route uses the next-hop 2001:db8:0:2::1, which is R1's own G0/1 address, causing a routing loop. Correct the route by specifying a directly connected remote next-hop (2001:db8:0:2::2) either with or without the exit interface. Set the floating static default route with an AD higher than the dynamic route's default AD (e.g., 254) so it becomes a backup. Option A (exit interface + next-hop) and Option D (next-hop only) both achieve this; Options B and C fail due to wrong next-hop or AD.

Answer

Change the IPv6 static route to '2001:db8:1::1/128 2001:db8:0:2::1' and set the floating default route's AD to 1.

Answer

Change the IPv6 static route to '2001:db8:1::1/128 GigabitEthernet0/1 2001:db8:0:2::2' and set the floating default route's AD to 1.

Question 14

You are connected to R1 via the console. Configure single-area OSPFv2 on R1 and R2 so that they form a full adjacency. The link between R1 and R2 uses 203.0.113.0/30. R1 has G0/0 203.0.113.1/30 and R2 has G0/0 203.0.113.2/30. R1's router-id must be 1.1.1.1, and R2's router-id must be 2.2.2.2. R1's GigabitEthernet0/0 interface is configured as a passive interface under OSPF, preventing OSPF hello messages from being sent out of that interface. Ensure that R1 does not send OSPF hellos out of its loopback0 interface (203.0.113.129/32). After configuration, verify the adjacency is established and OSPF routes are exchanged.

Accepted Answer

The adjacency fails because R1's GigabitEthernet0/0 interface is configured as passive-interface. Remove the passive-interface command for G0/0.. The adjacency fails because R1's GigabitEthernet0/0 interface is configured as passive-interface (the 'No Hellos' line in show ip ospf interface). This prevents R1 from sending OSPF hellos to R2. To fix, remove the passive-interface command for G0/0. The loopback0 interface should remain passive. After removal, verify with 'show ip ospf neighbor' to see the neighbor state change to FULL and 'show ip route ospf' to see routes.

Answer

The adjacency fails because the router-id 1.1.1.1 is not reachable from R2. Configure a static route for 1.1.1.1/32 on R2.

Answer

The adjacency fails because the subnet mask on the link is /30 but OSPF expects a /24. Change the mask to /24 on both interfaces.

Answer

The adjacency fails because OSPF is not enabled on R2's GigabitEthernet0/0 interface. Configure 'ip ospf 1 area 0' on R2's G0/0.

Question 15

You are connected to R1 via console. R1 and R2 are directly connected via GigabitEthernet0/0. Configure OSPF process 1 on both routers so that they form a full adjacency. R1's router-id must be 1.1.1.1, and R2's router-id must be 2.2.2.2. Use network statements to advertise the direct link. Ensure that R1 does not send OSPF hellos out of its GigabitEthernet0/1 interface. The current configuration on R1 has mismatched hello and dead timers, and an incorrect network type, preventing adjacency. Fix all issues.

Accepted Answer

On R1, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under interface GigabitEthernet0/0, and ensure network type is broadcast. On R2, configure 'router-id 2.2.2.2' under router ospf 1. Also, on R1, add 'passive-interface GigabitEthernet0/1' under router ospf 1.. The adjacency was failing because R1 had incorrect hello (30) and dead (120) timers, while R2 used defaults (10/40). Additionally, R1’s network type was set to a non-broadcast type, causing a mismatch. To fix, on R1’s GigabitEthernet0/0, set hello-interval 10, dead-interval 40, and network type broadcast. In OSPF process 1 on R1, configure passive-interface GigabitEthernet0/1 to suppress hellos on that interface. On R2, under router ospf 1, set router-id 2.2.2.2. Option A addresses all requirements. Option B uses wrong timers and passive-interface default, which blocks hellos on all interfaces, breaking adjacency. Option C sets network type point-to-point, creating a type mismatch with R2’s broadcast, preventing adjacency. Option D omits the passive-interface command, failing to suppress hellos on GigabitEthernet0/1 as required.

Answer

On R1, configure 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120' under interface GigabitEthernet0/0, and set network type to point-to-point. On R2, configure 'router-id 2.2.2.2' under router ospf 1. Also, on R1, add 'passive-interface default' under router ospf 1.

Answer

On R1, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under interface GigabitEthernet0/0, and set network type to point-to-point. On R2, configure 'router-id 2.2.2.2' under router ospf 1. Also, on R1, add 'passive-interface GigabitEthernet0/1' under router ospf 1.

Answer

On R1, configure 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40' under interface GigabitEthernet0/0, and ensure network type is broadcast. On R2, configure 'router-id 2.2.2.2' under router ospf 1. Also, on R1, add 'network 10.0.0.0 0.255.255.255 area 0' under router ospf 1.