# Layer 2 Loops

## Broadcast Storms

<figure><img src="https://1474932522-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FAgItg4KAZpnXjAFPWRf8%2Fuploads%2FyuJvoPBIPtBLbje9uFkb%2F2023-01-28_17-21.png?alt=media&#x26;token=ab3b6d6a-1c73-454d-870c-faf23955ddf9" alt=""><figcaption><p>What is the problem in this network ?</p></figcaption></figure>

<figure><img src="https://1474932522-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FAgItg4KAZpnXjAFPWRf8%2Fuploads%2Fxumc7WSRGK0SNUN7EKSd%2F2023-01-28_17-21.png?alt=media&#x26;token=1c37198a-b350-4751-9d36-57e34def00f0" alt=""><figcaption><p>Sw3 and SW2 will continue to flood the ARP requests forever</p></figcaption></figure>

The Ethernet header doesn't have a TTL field. these broadcast frames will loops around the network indefinitely. If enough of these looped broadcasts accumulate in the network, the network will be too congested for legitimate traffic to use the network. This is called a **broadcast storm**.

Network congestion isn't the only problem. Each time a frame arrives on a switch port, the switch uses the source MAC address field to _learn_ the MAC address and update its MAC address table. When frames with the same source MAC address repeatedly arrive on different interfaces, the switch is continuously updating the interface in its MAC address table. This is known as **MAC Adress Flapping**.
