200-301 Question #1659: Real Exam Question with Answer & Explanation

Question

Lab Simulation 50 Guidelines This is a lab item in which tasks will be performed on virtual devices. - Refer to the Tasks tab to view the tasks for this lab item. - Refer to the Topology tab to access the device console(s) and perform the tasks. - Console access is available for all required devices by clicking the device icon or using the tab(s) above the console window. - All necessary preconfigurations have been applied. - Do not change the enable password or hostname for any device. - Save your configurations to NVRAM before moving to the next item. - Click Next at the bottom of the screen to submit this lab and move to the next question. - When Next is clicked, the lab doses and cannot be reopened. Topology Tasks All physical cabling is in place. Router R4 and PC1 are fully configured and inaccessible. R4's WAN interfaces use .4 in the last octet for each subnet. Configurations should ensure that connectivity is established end-to-end. 1. Configure static routing to ensure R1 prefers the path through R2 to reach only PC1 on R4's LAN 2. Configure static routing that ensures traffic sourced from R1 will take an alternate path through R3 to PC1 in the event of an outage along the primary path 3. Configure default routes on R1 and R3 to the Internet using the least number of hops Answer: See the below explanation

Options

• taskEnsure that connectivity is established end-to-end.
• prerequisites

Explanation

Lab Simulation 50 — Static Routing & Floating Routes Explanation

Overall Goal

The topology has R1 connected to two paths toward R4's LAN (where PC1 lives): one through R2 (primary) and one through R3 (backup). There is also an Internet-facing connection. The goal is to configure static routing to control path preference, provide failover, and enable Internet access — without a routing protocol.

Step 1: Primary Static Route (R1 → R2 → R4's LAN)

What it does: Installs a specific host or subnet route on R1 pointing to R4's LAN via R2's interface.

Why it's necessary: Without this, R1 has no knowledge of PC1's subnet. A static route with default administrative distance (AD = 1) via R2 makes R2 the preferred path.

Command pattern:

R1(config)# ip route <PC1-subnet> <mask> <R2-next-hop>

Key detail: "Reach only PC1 on R4's LAN" means you target the specific LAN subnet (not a default route), keeping the route specific so it doesn't catch unintended traffic.

Step 2: Floating Static Route (R1 → R3 → R4's LAN, backup)

What it does: Installs the same destination route via R3, but with a higher AD (e.g., AD = 5 or any value > 1).

Why it's necessary: If both routes had the same AD, the router would load-balance or pick arbitrarily. A higher AD makes this route floating — it only enters the routing table when the primary route (via R2) disappears (link down, next-hop unreachable).

Command pattern:

R1(config)# ip route <PC1-subnet> <mask> <R3-next-hop> 5

What goes wrong if skipped: During an R2 outage, R1 would have no route to PC1 — traffic blackholed.

Step 3: Default Routes on R1 and R3 to the Internet

What it does: Installs a 0.0.0.0 0.0.0.0 route pointing toward the Internet gateway using the fewest hops.

Why "least number of hops" matters: If R1 has a direct link to the Internet gateway, configure R1's default route to point there directly rather than routing through R3 first. Same logic applies to R3 — use its own directly connected path if available, not a multi-hop path.

Command pattern:

R1(config)# ip route 0.0.0.0 0.0.0.0 <internet-gateway-next-hop>
R3(config)# ip route 0.0.0.0 0.0.0.0 <internet-gateway-next-hop>

What goes wrong if skipped: R1 and R3 can't reach the Internet — any traffic to unknown destinations is dropped.

What Goes Wrong If Steps Are Out of Order or Skipped

Memory Tip

Think "Specific → Floating → Default":

• Specific route first (precise destination, preferred path, AD=1)
• Floating backup second (same destination, higher AD, alternate path)
• Default route last (catch-all for Internet, minimize hops)

This mirrors the order of route specificity: most specific routes win, defaults catch everything else.

Don't Forget

Always write memory (or copy run start) before moving on — the lab explicitly requires saving to NVRAM.

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