5.3 Given a scenario, troubleshoot common issues with network services
Addressing Issues
📘CompTIA Network+ (N10-009)
1. What is an IP Pool?
An IP pool is a range of IP addresses that a network device (usually a DHCP server) can assign to devices on the network.
- DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices (like computers, printers, and phones) so they can communicate on the network.
- The IP pool is like a “list of available IP addresses” that the DHCP server can give out.
Example:
If a DHCP server has an IP pool of 192.168.1.100 to 192.168.1.200, it can assign up to 101 devices unique IP addresses from that range.
2. What is IP Pool Exhaustion?
IP pool exhaustion happens when all the IP addresses in the DHCP server’s pool are already assigned, and new devices cannot get an IP address.
- When a device tries to connect and there’s no free IP address, it fails to get a network connection.
- This can result in devices having no internet access or being unable to communicate on the local network.
3. Causes of IP Pool Exhaustion
IP pool exhaustion usually occurs due to:
- Too many devices on the network
- More devices are connecting than the DHCP pool can handle.
- Long DHCP lease times
- A DHCP lease is how long a device can keep its assigned IP address.
- If lease times are very long, IP addresses stay “reserved” even when devices are offline, reducing available addresses.
- Misconfigured DHCP pools
- If the DHCP pool is too small for the network size, it can run out quickly.
- Stale IPs / Leases not being released
- Sometimes devices disconnect but the DHCP server does not free the IP, causing unnecessary exhaustion.
4. Symptoms of IP Pool Exhaustion
When IP pool exhaustion occurs, network administrators and users may notice:
- Devices fail to get an IP address (often showing APIPA address like
169.254.x.x). - Users cannot access network resources (servers, printers, internet).
- DHCP server logs may show “no available IP addresses” or similar messages.
5. How to Troubleshoot IP Pool Exhaustion
Here are step-by-step actions:
- Check the DHCP server pool size
- Make sure the pool has enough IPs for all devices.
- Look at DHCP lease times
- Shorten lease times if devices are frequently joining and leaving the network.
- Check for inactive or stale IP addresses
- Release or remove old leases that are no longer used.
- Increase the IP pool
- Add more IP addresses to the DHCP scope if the current pool is too small.
- Segment the network
- Use VLANs or multiple subnets to reduce the number of devices in a single DHCP pool.
6. Preventing IP Pool Exhaustion
To avoid running out of IPs:
- Plan your DHCP pool size according to the number of devices on the network.
- Use subnetting to create separate pools for different groups.
- Monitor DHCP usage regularly.
- Implement DHCP failover for redundancy.
7. Key Exam Points to Remember
For the Network+ exam, remember:
- Definition: IP pool exhaustion is when all available IPs in a DHCP pool are used.
- Symptoms: Devices fail to get IP addresses, show
169.254.x.x, or lose connectivity. - Causes: Too many devices, long leases, small DHCP pool, stale leases.
- Troubleshooting steps: Check pool size, lease times, release stale IPs, expand pool, segment network.
This explanation is complete for the exam and uses IT-related examples without confusing metaphors.
