Do you know what a network loop is? Have you ever had a loop in your LAN? No matter you want it or not, a loop in the LAN can bring down your whole network.

First, let’s see what a network loop is. A network loop is a network configuration there is more than one path between two computers or devices, which causes packets to be constantly repeated. This is due to the fact that a hub will blindly transmit everything it receives to all connections – other devices, such as switches and routers, might be able to reduce or eliminate this problem.

In this article, I’m going to show you how to find out the network loop with Capsa?

Let’s start Capsa, and then add in the packet file into the ready-to-replay list. Without any other settings, click this icon to start replay directly.

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First we come to the Dashboard tab. The graphs show that the traffic is not big. We can conclude that, no machine is keeping sending a large sum of packets, to block the bandwidth.

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We can sure from the Protocol tab, that only ICMP is used in the traffic. However, in Diagnosis tab, there is one record, IP TTL too low, which means a packet has passed too many routers.

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And we can see the anomaly happens at IP address, one seventy two, dot sixteen, dot two zero eight, dot thirty three. Let’s start from this address. Right-click on the address, and locate it.

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Then, go directly to the packet tab. We can see all the packets are ICMP packets. And we find the delta time between the packets is very small, and there are more than twelve thousand packets. This couldn’t be normal. Just a simple ping can’t produce so many packets, it looks like network loop a little bit.

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