How to rate limit incoming bandwidth for an entire subnet?

Linux Troubleshooting
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1

Hello all,

How do I impose bandwidth restrictions on incoming packets across an entire subnet using tc in Alma Linux 8, 9, and later?

Thanks, Jenn

2

Hi,

You can use the tc (traffic control) utility combined with an ifb (Intermediate Functional Block) device to limit incoming traffic rates for an entire subnet. The following commands provide a step-by-step process to set this up:

Load and activate the IFB module

modprobe ifb

ip link set dev ifb0 up

Clear any existing traffic control configurations

tc qdisc del dev enp1s0 root

tc qdisc del dev ifb0 root

tc qdisc del dev enp1s0 ingress

Attach an ingress qdisc to the network interface

tc qdisc add dev enp1s0 ingress

Redirect incoming subnet traffic to the IFB device

# tc filter add dev enp1s0 parent ffff: protocol ip prio 1 u32 match ip src 192.0.2.0/255.255.255.0 action mirred egress redirect dev ifb0

Set up HTB shaping on the IFB interface

# tc qdisc add dev ifb0 root handle 1: htb default 30

# tc class add dev ifb0 parent 1: classid 1:1 htb rate 20mbit ceil 20mbit

Apply traffic filtering and shaping rules

tc filter add dev ifb0 protocol ip parent 1: prio 1 u32 match ip src 192.0.2.0/255.255.255.0 flowid 1:1

Here are examples where the tc command was executed on the server, followed by transferring a file via scp to verify the speed under a 20 Mb/s restriction.

# scp TestFile root@192.168.1.1:/root
root@192.0.2.50's password: 
TestFile                                                        100%  200MB   2.3MB/s   01:11    

# scp TestFile root@192.158.1.1:/root
root@192.0.2.50's password: 
sample_40MB_file3                                               100%   40MB   2.4MB/s   00:20

Let me know if it solves at your end.

Richard :folded_hands: