100-490 Service-Related Knowledge
Service-Related Knowledge
Detailed list of 100-490 knowledge points
Service-Related Knowledge (Additional Content) Detailed Explanation
1. Common Command Recognition – Exam-Focused Tips
Some Cisco exam questions focus on identifying the correct command to achieve a specific result. These are often presented in a direct or situational format.
Commonly Tested Command Prompts:
| Task Description | Correct Command |
|---|---|
| Display all interfaces with IPs and status on one line | show ip interface brief |
| Display detailed statistics on a specific interface | show interfaces [interface-id] |
| Display the device’s full system version and uptime | show version |
| Display the current configuration in RAM | show running-config |
| Display stored log events and errors | show logging |
| Display routing table information | show ip route |
| Show all hardware and module inventory | show inventory |
| Show temperature, fan, and power supply conditions | show environment |
Exam Tip:
You may see questions like:
“Which command shows a concise list of interface statuses and IP addresses?”
→ Answer: show ip interface brief
2. TFTP and Firmware Upgrade – Common Errors and Solutions
TFTP-based upgrades are straightforward but can fail due to network, configuration, or compatibility issues. Understanding error symptoms and their causes is critical.
Common TFTP Upgrade Errors and Troubleshooting:
| Error Message / Symptom | Likely Cause | Solution |
|---|---|---|
| %Error: Timeout expired | TFTP server unreachable | Verify network connectivity (ping TFTP server) |
| Firewall blocking TFTP (UDP port 69) | Temporarily disable firewall or allow UDP 69 | |
| Incorrect server IP or file name | Double-check TFTP address and filename | |
| Invalid IOS image or CRC error | File is corrupt or incomplete | Re-download image and verify checksum |
| Image not supported | Incompatible image for the hardware | Check platform model and use proper IOS version |
| Flash memory full | Not enough space on device | Delete unused files or expand flash (if supported) |
Best Practices Before Upgrading:
Ping the TFTP server from the device to confirm reachability.
Use
dir flash:to check available space.Use
verify /md5 flash:<filename>(if available) to confirm file integrity.
3. Preparing Device Information for TAC Support Cases
When opening a case with Cisco’s Technical Assistance Center (TAC), it’s essential to provide relevant technical details up front. This helps accelerate diagnosis and resolution.
Information Typically Required:
| Item | Purpose |
|---|---|
| Device Serial Number | Identifies the physical hardware and validates support status |
| IOS Version | Helps identify known bugs or compatibility issues |
| Platform Model | Ensures the TAC engineer understands the device's capabilities |
| Recent Logs / Error Messages | Clarifies the scope of the issue |
| Command Outputs | Must-have outputs include: |
show version – System summary |
|
show tech-support – Full diagnostic data |
Sample Real-World Flow:
Log in to the device via console or SSH.
Run the following commands:
show version
show tech-support
Save the output to a
.txtfile.Open a TAC case via Cisco Support Portal and attach the collected logs along with a detailed problem description.
Exam Tip:
You may encounter scenario-based questions such as:
“A support engineer asks you to provide diagnostic outputs. Which command should you use?”
→ Answer: show tech-support
Frequently Asked Questions
How do you establish a console connection from a laptop to a Cisco router or switch?
Use a console cable between the laptop and the device console port, then open a terminal emulator such as PuTTY with the correct serial settings.
The console cable connects the laptop’s USB or serial port to the Cisco device’s console port. After connecting the cable, a terminal emulator such as PuTTY or Tera Term must be configured with standard serial settings: 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control. Once the connection is opened, pressing Enter should display the device CLI prompt. If the screen appears blank, incorrect COM port selection or incorrect serial parameters are common causes.
Demand Score: 74
Exam Relevance Score: 90
Why might a TFTP transfer fail during a Cisco IOS upgrade?
A TFTP transfer may fail due to incorrect IP configuration, firewall blocking UDP port 69, or an unreachable TFTP server.
TFTP relies on UDP communication and requires IP connectivity between the device and the server. If the router interface lacks a correct IP address or subnet configuration, the transfer cannot start. Firewalls on the server computer may also block UDP port 69, preventing file transfers. Another common issue occurs when the TFTP root directory does not contain the correct image file. Engineers must verify connectivity using ping before starting the transfer and ensure the file name matches exactly.
Demand Score: 80
Exam Relevance Score: 92
What is the purpose of configuring an IP address on a laptop Ethernet interface when servicing Cisco devices?
It allows the laptop to communicate with the Cisco device over the network for configuration, file transfer, or management tasks.
When connecting directly to a switch or router Ethernet port, the laptop must have an IP address in the same subnet as the device interface. This enables communication using protocols such as SSH, Telnet, FTP, or TFTP. Without proper IP configuration, the laptop cannot reach the device even if the physical cable connection is correct. Technicians often configure temporary IP settings when performing upgrades or copying configuration files. Incorrect subnet masks or missing default gateways may also prevent connectivity.
Demand Score: 72
Exam Relevance Score: 86
What is the basic procedure used to recover a lost enable password on a Cisco router?
The device is rebooted into ROMMON mode, the configuration register is changed to ignore the startup configuration, and the password is reset.
During password recovery, the engineer interrupts the boot sequence to enter ROMMON mode. The configuration register is modified so the router ignores the saved configuration during boot. This allows the router to start without requiring the previous password. After accessing privileged mode, the original configuration can be loaded and the password changed. Finally, the configuration register is restored to its default value and the configuration is saved. This process preserves existing configurations while allowing administrative access.
Demand Score: 79
Exam Relevance Score: 93
What common Layer 1 or Layer 2 issues can cause an Ethernet interface to show a down or unstable status?
Common causes include faulty cables, incorrect duplex settings, mismatched speed settings, or disconnected physical links.
Layer 1 problems typically involve hardware issues such as damaged cables, incorrect connectors, or disconnected ports. Layer 2 issues often involve mismatched interface settings, such as one side configured for full duplex while the other uses half duplex. Speed mismatches can also cause packet errors and unstable links. Engineers should check interface status using commands like show interface and verify both sides of the connection use compatible settings. Troubleshooting usually begins by verifying the physical connection before examining configuration problems.
Demand Score: 76
Exam Relevance Score: 90
