How to Search Logs by IP Address

Logging IP addresses is one way to track down the source of a web application. For this purpose, you can use the DHCP server’s logging of IP addresses, the X-Forwarded-For header, or UDP port 1024. If you are using a logging tool like Scalyr, you can also use the Scalyr log indexing service. It can index your logs in real time.

DHCP server logs IP address allocation

If you’re wondering how your DHCP server allocates IP addresses, you’re not alone. It’s very common for DHCP servers to log the IP addresses allocated to clients. Typically, these logs are complete and contain the DHCP server’s numeric IP address and domain name. The IP address logged by a DHCP server is stored in the PATH_DHCPD_PID environment variable.

X-Forwarded-For header

If you’re using HTTP proxy and want to log the IP address of a visitor, you can look for an X-Forwarded-For header (XFF). The XFF header identifies the client’s IP address when the visitor is connected through a proxy server. It’s important to note that this header is vulnerable to forging. Fortunately, there’s a simple solution.

UDP port 1024

You should be able to find out what IP address is being used by a server when logging UDP port 1024 traffic. TCP/UDP port numbers from 0 to 1023 are considered well-known ports, while 1024 to 49151 are considered semi-reserved. ThisĀ range is used for web browsers.

Scalyr indexes your logs in real-time

Scalyr is a powerful log management and analytics platform for web servers. Its real-time indexing technology enables you to search through logs by IP address and create custom reports. The interface is straightforward and easy to use, with five main tabs to guide you through the process. The dashboard features colorful graphs and easy-to-understand data. You can also expand individual graphs to drill down into key metrics. These include CPU load average, CPU usage, disk and memory usage, and disk request bandwidth and latency.

Privacy risk

An IP address is a great way to identify users. However, it also presents a privacy risk since it is tied to personal information, including email addresses. However, there are ways to mitigate the risk of your IP address being linked to PII. One option is to create a user account without entering PII. For instance, an account created with a disposable email address or with Bitcoin won’t be traceable to a specific individual.


IP address logging is an important part of network security. Often overlooked, IP addresses can cause significant ripple effects in a network and can be difficult to detect. Fortunately, there are a number of solutions available for IP address logging.