Questions and Answers
PC1 addresses a packet to PC3 and sends it to the default ______ address.
gateway
When the packet arrives on the R1 G0/0/0 interface, R1 ______ the packet and searches the routing table.
decapsulates
If the destination IP address matches a static ______ entry, R1 will use it to identify the next-hop IP address.
route
If the packet does not match a specific route, then R1 will use the ______ static route.
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If no route table entry matches, R1 will ______ the packet and send an ICMP message back.
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Assuming R1 matched a routing table entry, it encapsulates the packet in a new ______ and forwards it.
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R2 receives the packet on its S0/1/0 interface and ______ the packet the same way R1 did.
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R1 will drop the packet and send an ICMP ______ back to the source.
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The command ______ verifies the path to the destination network.
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The command ______ displays the routing table.
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To verify the operational status of an interface, you can use ______.
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______ displays a list of directly connected Cisco devices.
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Connectivity from PC1 to PC3 fails when extended pings from R1 G0/0/0 interface to ______ fail.
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Pings from R1 to R2 are successful, suggesting that R1 can reach ______.
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The R2 routing table reveals that the ______ of last resort is not set.
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The command to reveal the routing path can show that the static route was ______.
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A new static route ultimately ______ the connectivity problem.
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The subnet 172.16.0.0/16 is variably ______.
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When R2 finds a match in the routing table, it uses the identified next-hop IP address or exit interface and sends the packet out of its interface S0/1/1 towards ______.
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R3 searches the routing table for a match. The destination IP address of PC3 matches the directly connected ______ interface.
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If no ARP entry exists, then R3 sends an ARP request out of the ______ interface.
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PC3 responds with an ARP reply containing its ______ address.
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R3 encapsulates the packet in a new frame and uses the PC3 MAC address as the destination MAC address and the ______ MAC address as the source MAC address.
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Common reasons for network failures include interface failure, service provider drops, link oversaturation, or a wrong ______ entered by an administrator.
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Network administrators are responsible for pinpointing and solving the ______.
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To efficiently find and solve network issues, it is advantageous to be intimately familiar with tools to help isolate ______ problems quickly.
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One common troubleshooting command is ______, which verifies Layer 3 connectivity to a destination.
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Extended pings provide ______ options.
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When the destination IP address matches a directly connected Ethernet ______, the router searches the ARP table.
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If no ARP entry exists, the router sends an ______ request out of the Ethernet interface.
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The router encapsulates the packet in a new ______ before forwarding it.
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The frame uses the MAC address of the destination host as the frame destination ______ address.
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Common IOS troubleshooting commands include ping, traceroute, and show ip ______.
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A host sends a packet to another host and sends it to the default ______ address.
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When the packet arrives on a router interface, it ______ the packet and searches the routing table.
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The static route command is used to configure an ______ route.
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The static route to 172.16.3.0 uses the subnet mask ______.
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The routing table entry 192.168.1.0/24 is marked as ______.
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In the output, S stands for a ______ route.
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Troubleshooting routes can involve repairing errors in both static and default ______.
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To troubleshoot IPv6 static routes, you must also configure ______ static routes.
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When gathering information to troubleshoot, creating an ______ plan is essential.
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The routing entry 192.168.2.0/24 points to the next hop at ______.
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Study Notes
Module Overview
- Focus on troubleshooting static and default routes within networking environments.
- Develop skills for packet processing and identifying configuration issues.
Packet Processing with Static Routes
- Static Routes: Defined paths for data packets used when specific routes are configured.
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Packet Journey:
- When a packet is sent from a source (e.g., PC1 to PC3), it first goes to the default gateway.
- Routers (e.g., R1) decapsulate packets, search routing tables, and make forwarding decisions based on matches.
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Routing Outcomes:
- If the destination IP matches a static route, the router forwards the packet using that route.
- If no specific match is found but a default route exists, the router uses the default route.
- If there’s no match at all, the packet is dropped and an ICMP message is sent back to the sender.
Continuation of Packet Processing
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Routing Process:
- Each router (R1, R2, R3) repeats the same decapsulation and lookup process on receiving packets.
- Packet encapsulation occurs again for forwarding to subsequent routers until it reaches the final destination.
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ARP Process:
- When the destination (PC3) is identified, the router checks the ARP table for the MAC address.
- If no entry exists, an ARP request is made to obtain the MAC address, which is then used for final packet encapsulation and forwarding.
Troubleshooting IPv4 Static and Default Route Configuration
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Common Networking Failures:
- Interface failure, oversaturation of links, and human error in configuration can lead to connectivity issues.
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Diagnostic Approach:
- Network administrators should utilize troubleshooting tools and commands to diagnose routing problems.
Common Troubleshooting Commands
- ping: Confirms Layer 3 connectivity to a destination.
- traceroute: Maps the path packets take to a destination, revealing possible network issues.
- show ip route: Displays the routing table, helping check correct IP entries.
- show ip interface brief: Provides a quick overview of interface statuses and IPs.
- show cdp neighbors: Shows connected Cisco devices to validate Layer 1 and Layer 2 connectivity.
Solving Connectivity Problems
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Example Scenario: Troubleshoot failed connectivity from PC1 to PC3.
- Successful pings from R1 to its adjacent routers indicate operational links.
- Use "show ip route" to check routing tables for misconfigured gateways or static routes.
- Rectify issues by removing incorrect static routes and adding correct ones to restore connectivity.
Module Practice and Quiz
- Understand packet flow from a sender to a receiver through routers.
- Emphasis on router actions (decapsulation, routing table lookups, ARP resolutions).
- Appreciation of common IOS commands for troubleshooting static and default routes covering both IPv4 and IPv6.
Key Takeaways
- Mastering the process of packet routing is essential for effective network management.
- Familiarity with troubleshooting commands is critical for rapid diagnosis and resolution of network issues.
Studying That Suits You
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Description
Test your knowledge with this quiz on troubleshooting static and default routes in switching and routing. This module covers essential concepts and objectives related to packet processing and router configurations. Ensure you understand how routers handle static routes effectively.
