Getting lot of unwanted broadcasts on my network

Question

I am pretty new in Networking (noob), while I was monitoring my network using Wireshark, and I found that there is a lot of broadcasts happening all over the network, broadcast on Local network usually MDNS, NBNS, ARP (Gratitious), UDP[x.x.x.255], UDP[255.255.255.255].

I wonder whether these broadcast are the reason users facing dips in bandwidth? And How I can mitigate it? Can these broadcast be responsible for packet drops? Also I do not understand user systems are generating ARP broadcast? Doesn't my router should do the same?

Network Topology: We have a simple network consist of a switch (Cisco) which is between the gateway and rest of the Access Points (Ubiquiti) where access points are in Mesh Configuration. Rest of the users are connected an Access Point via WiFi.

Using Ethernet wire CAT-6 (between Router-Switch and Switch-Access_point),

User Count: 50

Wifi freqency: 2.4/5GHz

ISP Bandwidth: 150 MBps (Aggregated)

(Excuse my drawing skills)

Update This is latest output of broadcast I/O Graph

Answer 1

30 broadcasts/s at 100 bytes each translates to roughly 25 kbit/s. That is not a bandwidth problem with Ethernet, not even remotely.

As Ron T. has commented, the broadcast rate is somewhat high and might indicate other problems you have. You'll need to analyze the broadcasts for common reasons.

For instance, your snapshot indicates several ARP requests for the same IP 192.168.1.143 that may be configured for some central service but might currently be offline.

Additionally, the frequent NBNS broadcasts indicate a problem with DNS. You should run a DNS server that can resolve all commonly used names (or not). Once that's working you should disable broadcast resolution on all nodes.

Also, the broadcasts may be entirely unrelated to your problems. Basic LAN troubleshooting includes:

• check cabling/L1 connectivity for unexpected link changes and high error rates
• check L2 connectivity (VLANs) for source/dest MAC presence
• check L3 connectivity (ping) for local peers and gateway(s)
• check L3 connectivity (ping, lookup) for DNS server(s)
• check L3 connectivity (ping, traceroute, service access) for additional servers

Wireless LAN/Wi-Fi complicates things quite a bit. Check cabled nodes first and makes sure everything's fine there. Then, you need to make sure that the used channel(s) are not completely overloaded and there is no radio interference from machinery nearby. For a more detailed diagnosis a thorough survey may be required.