What’s a broadcast storm?
In this article, we will discuss about a broadcast storm and its effects and how we can eliminate them.
A Broadcast Storm is basically a situation when an abruptly large number of broadcast packets in a very small amount of time. Due to the broadcast storm, the network quality degrades significantly. It leads to broadcast and multicast traffic accumulation on a computer network.
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This condition can lead to consume all the network, so, it will be unable to transfer normal amount of traffic at that time. A Broadcast Packet that leads to such situation is often called Chernobyl Packet.
Types of Broadcast Packets :
Mainly, there are 3 types of Broadcast Packets :
A Broadcast packet uses Air as a medium to transfer the broadcast to any listener at the same frequency. A broadcast packet uses the destination header in the following ways :
- ff-ff-ff-ff-ff-ff (Layer 2 broadcast)
- 255.255.255.255 (Layer 3 broadcast)
Root Causes of a Broadcast Storm :
- When a user wants to connect to a specific hub of network but, by mistake, it gets connected to another switch port. This will catch all the frames and keep them within the loop. For Example – When the computer connects to port while being connected to wireless network also, the network sets to bridging mode.
- Improper VLAN configuration settings can create a loop that finally leads to a broadcast storm.
- Too big Broadcast Domain – If the Broadcast is too big, then the amount of traffic in a domain is directly proportional to size of the broadcast domain, i.e. the number hosts in a L2 VLAN or L3 subnet.
- High Volume of requests for IP address via DHCP – DHCP is the most easiest way for a networking host to get the IP address from a network controller. DHCP uses either broadcast or unicast packets as their medium. For Example – when the network is back online after a outage, all the members on that network try to obtain the IP address.
Steps to prevent a Broadcast Storm :
- Anti-virus Firewalls can be used to detect and remove malicious and intentionally induced broadcast storms to disrupt the network.
- The more often ARP tables are cleared, the more often broadcast requests occur.
- Storm protocols and equivalent controlling techniques allow to limit the broadcast packets.
- Disable broadcasts on Layer 3 devices. If a storm originated from the WAN, then shutting off IP directed broadcasts will solve the issue.
- Splitting the broadcast domain will help in diverting the broadcast traffic. By creating a new VLAN network, we can divert more half of the traffic to the other network. It will help in reducing the storms a lot.
- Regular maintenance of Switches ensure that they don’t face any hardware failure.
- Checking for loops in switches help to upstream the unmanaged switch. The unmanaged switches in order to respond to the broadcasts sometimes flood the network with a lot of unnecessary traffic.
To summarize all the above, the following elements play an effective role in creating a broadcast storm:
- Poor network management
- Poor monitoring of the network
- The use of cheap hubs & ports
- Improper network configuration
- The lack of a network diagram design, needed for proper management and to provide guidelines for all network traffic routes