Bandwidth Limiting HOWTO With Linux, Tc And Iproute2

I've seen a lot of requests for a simple howto dealing with bandwidth limiting/"capping" on Linux. I put together a howto yesterday on this which I hope you'll find useful.

I�fve recently optimized the scripts used for bandwidth management in one of our UK facilities and I thought I�fd post a quick howto on it.

The full script can be found directly here: http://www.adamsinfo.com/bandwith-li...oute2/#more-15

My setup here is a live feed entering eth0 on this linux router and leaving eth1 into a switch connected to a collection of other servers. This is set up as an unrestricted public router, routing between a /30 on eth0 and a /24 on eth1.
Note: We can�ft in any way restrict the amount of traffic that eth0 receives from the outside, so instead we restrict how fast eth0 sends data out, the same applies the other way round. So, if we want to limit the amount of data that the local servers can send, we shape the router�fs external interface (eth0). If we want to limit the amount of data that the local servers can receive, we shape the router�fs internal interface (eth1)

With Debian Etch on 2.6.x, run:
apt-get install tc iproute2 bc

Then script as follows:
# Set some variables
#!/bin/bash
EXT_IFACE=�heth0��
INT_IFACE=�heth1��
TC=�htc�h
UNITS=�hkbit�h
LINE=�h10000�� #maximum ext link speed
LIMIT=�h5000�� #maximum that we�fll allow


# Set some variables for individual �gclasses�h that we�fll use to shape internal upload speed, i.e. shaping eth0
CLS1_RATE=�h200�� # High Priority traffic class has 200kbit
CLS2_RATE=�h300�� # Medium Priority class has 300kbit
CLS3_RATE=�h4500�� # Bulk class has 4500kbit
# (We�fll set which ones can borrow from which later)

# Set some variables for individual �gclasses�h that we�fll use to shape internal download speed, i.e. shaping eth1
INT_CLS1_RATE=�h1000�� #Priority
INT_CLS2_RATE=�h4000�� #Bulk

[...] A few hundred lines [...]

I have tried not to get bogged down with too many irrelevant details here and would be happy to answer any questions or take any corrections. It�fs pretty simple and it works well. Install bmon and you can confirm this yourself. The purpose of this is that I can take a 10mbit connection and limit the traffic to 5mbit ensuring that I don�ft break the 95th percentile that I want to maintain at the datacenter. I can increase and decrease this at any time as traffic requires or permits respectively.