CCNA IP Routing Practice Question
Which static route on R1 sends all unknown IPv4 destinations to next-hop address 192.0.2.1?
⚠ Common exam trap
A frequent exam trap is selecting a static route with the destination 0.0.0.0 but an incorrect subnet mask like 255.255.255.255, which matches only the single host 0.0.0.0 rather than all unknown destinations. Another common mistake is confusing the 'ip default-gateway' command with a default route; the former is used only on devices that do not perform routing, such as Layer 2 switches, and does not influence routing decisions on routers. Candidates must recognize that the default route requires both destination and mask to be 0.0.0.0 to function correctly as a catch-all route for unknown IPv4 destinations.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ip route 0.0.0.0 0.0.0.0 192.0.2.1
A quad-zero route is the IPv4 default route. It matches destinations that do not have a more specific entry in the routing table.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ip route 0.0.0.0 255.255.255.255 192.0.2.1
Why it's wrong here
Specifying a mask of 255.255.255.255 with a destination of 0.0.0.0 creates a host route for the single address 0.0.0.0, not a default route. A /32 route can only match the exact source/destination address 0.0.0.0, so it cannot match normal unknown IPv4 destinations such as 198.51.100.1. Thus R1 would reject or drop traffic that has no more-specific match.
When this WOULD be correct
If the exam question asked for a specific route to a single host (e.g., 'Which static route on R1 sends traffic only for the IP address 0.0.0.0 to next-hop address 192.0.2.1?'), then option A would be correct as it defines a route for that specific host.
- ✓
ip route 0.0.0.0 0.0.0.0 192.0.2.1
Why this is correct
The command ip route 0.0.0.0 0.0.0.0 192.0.2.1 installs a default static route whose prefix and mask are both all zeros. Because the routing table uses longest-prefix-match, this quad-zero route matches every IPv4 destination that is not matched by a more specific route. R1 will therefore forward all unknown IPv4 traffic out the interface toward next-hop 192.0.2.1.
- ✗
ip route 255.255.255.255 0.0.0.0 192.0.2.1
Why it's wrong here
This command reverses the prefix and mask: in Cisco's ip route syntax, the first two fields are the destination network and its subnet mask. Using 255.255.255.255 as the prefix with mask 0.0.0.0 is not a valid representation of a default route; a default route must use 0.0.0.0 0.0.0.0. The all-ones network address with a zero mask would be interpreted as a broadcast/undefined pattern and would not cause R1 to send unknown destinations to 192.0.2.1.
When this WOULD be correct
This option would be correct in a scenario where the question asks for a route that matches a specific broadcast address, such as directing traffic for all broadcast packets to a next-hop address, which would be relevant in certain network configurations.
- ✗
ip default-gateway 192.0.2.1
Why it's wrong here
The ip default-gateway command is not a routing protocol or static route; it configures the gateway used by the device's own IP stack for management traffic when IP routing is disabled. On a router or multilayer switch that is forwarding IPv4 in hardware, ip routing must be enabled and a 0.0.0.0/0 static route (or dynamic protocol) is required. This command would not install an IPv4 route in R1's routing table and would not forward packets for other hosts.
When this WOULD be correct
If the exam question asked for the command to set a default gateway for a Layer 2 device like a switch, then 'ip default-gateway 192.0.2.1' would be the correct answer, as it would direct traffic to the specified gateway for devices that do not have a specific route.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓ip route 0.0.0.0 0.0.0.0 192.0.2.1Correct answer▾
Why this is correct
The command ip route 0.0.0.0 0.0.0.0 192.0.2.1 installs a default static route whose prefix and mask are both all zeros. Because the routing table uses longest-prefix-match, this quad-zero route matches every IPv4 destination that is not matched by a more specific route. R1 will therefore forward all unknown IPv4 traffic out the interface toward next-hop 192.0.2.1.
✗ip route 0.0.0.0 255.255.255.255 192.0.2.1Wrong answer — click to see why▾
Why this is wrong here
The mask 255.255.255.255 specifies a host route, meaning this route matches only the single IP address 0.0.0.0, not all destinations. A default route requires a mask of 0.0.0.0 to match any destination.
★ When this WOULD be the correct answer
If the exam question asked for a specific route to a single host (e.g., 'Which static route on R1 sends traffic only for the IP address 0.0.0.0 to next-hop address 192.0.2.1?'), then option A would be correct as it defines a route for that specific host.
Why candidates choose this
Students may confuse the all-zeros network address with a default route, but the mask is critical. Using a /32 mask is a common mistake when trying to create a default route.
✗ip route 255.255.255.255 0.0.0.0 192.0.2.1Wrong answer — click to see why▾
Why this is wrong here
The address 255.255.255.255 is a broadcast address, and the mask 0.0.0.0 is invalid for a default route. The correct syntax for a default route is 'ip route 0.0.0.0 0.0.0.0 next-hop'. This option has the network and mask reversed.
★ When this WOULD be the correct answer
This option would be correct in a scenario where the question asks for a route that matches a specific broadcast address, such as directing traffic for all broadcast packets to a next-hop address, which would be relevant in certain network configurations.
Why candidates choose this
Some test-takers might think that using all ones in the network field represents 'all networks', but this is incorrect. The default route uses all zeros for both network and mask.
✗ip default-gateway 192.0.2.1Wrong answer — click to see why▾
Why this is wrong here
The 'ip default-gateway' command is used on devices that do not run IP routing, such as Layer 2 switches, to provide a default gateway for management traffic. On a router, the correct command to set a default route is 'ip route 0.0.0.0 0.0.0.0'.
★ When this WOULD be the correct answer
If the exam question asked for the command to set a default gateway for a Layer 2 device like a switch, then 'ip default-gateway 192.0.2.1' would be the correct answer, as it would direct traffic to the specified gateway for devices that do not have a specific route.
Why candidates choose this
The term 'default-gateway' sounds similar to 'default route', leading students to believe it is the correct command for routers. However, routers use the 'ip route' command for static routing.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
Internet Protocol
Internet Protocol (IP) is the set of rules that governs how data is addressed, routed, and sent from one device to another across networks, including the internet.
Key term
Static route
A static route is a manually configured path in a router's routing table that tells the router exactly where to send packets for a specific destination network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.