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Check and tune network speed

Fri, 05/06/2011 - 16:56 — sandip

I've had to do this on a couple of servers to check on the network speeds and sysctl tuning.

On the receiving end (192.168.10.1) bring up netcat listening to a port:

while true; do nc -l 8001 >/dev/null ; done

Use the below one liner to send over some data via netcat from 192.168.10.2 which prints out the transfer speed.

( dd if=/dev/zero bs=64K count=1000 | nc 192.168.10.2 8001 ) 2>&1 | awk '/MB/{print $8*8 " " tolower($9)}'

Increase the default maximum TCP buffer size and rerun the above test for proper tuning. Make sure to restart netstat listening socket upon sysctl changes.

The following are recommended:

##
# max TCP buffer size: 16MB (16 * 1024 * 1024).
# Could increase to 32MB for GigE.
#
# Increasing the TCP send buffers will increase the performance
# if you have large files to send.
#
net.core.wmem_max = 16777216

# If you have a lot of large file uploads,
# increasing the receive buffers will help.
#
net.core.rmem_max = 16777216

# increase Linux autotuning TCP buffer limits:
# min, default, and max number of bytes to use
# (only change the 3rd value, and make it 16 MB or more)
#
net.ipv4.tcp_rmem = 4096        87380   16777216
net.ipv4.tcp_wmem = 4096        65535   16777216

# Support for the above large TCP send and receive windows.
# Needs to be set to 1 if the Max TCP Window is over 65535 (64K).
#
net.ipv4.tcp_window_scaling = 1

# Increase backlog to avoid dropped packets and increase throughput.
# Check with `netstat -st | grep packets` and check for
# dropped and packet errors.
#
net.core.netdev_max_backlog = 5000

Bridge Networking On OpenVZ Containers Using VETH Devices

Wed, 08/13/2008 - 23:52 — sandip

1. Host will be open on LAN and guests on WAN. Additionally, there is a bridged LAN for guests.
2. We will be using bridge networking for protecting the Host Network and saving IP addresses, also giving flexibility with the guest network setup.
3. Configure LAN Eth1 port to 192.168.1.2
4. WAN Eth0 port is not assigned any IP address.
6. Install the required bridge-utils package via:

yum install bridge-utils

* Network:

# cat /etc/sysconfig/network
NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=<host.domain.tld>
GATEWAY=192.168.1.1
GATEWAYDEV="eth1"

* WAN Bridge device br0:

# cat /etc/sysconfig/network-scripts/ifcfg-br0
DEVICE=br0
BROADCAST=xxx.xxx.xxx.xxx />NETMASK=255.255.255.24
NETWORK=xxx.xxx.xxx.xxx
ONBOOT=yes
GATEWAY=xxx.xxx.xxx.xxx
TYPE=Bridge

* WAN eth0 device:

# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
HWADDR=00:30:48:65:12:b4
ONBOOT=yes
TYPE=Ethernet
BRIDGE=br0

* LAN Bridge device br1:

# cat /etc/sysconfig/network-scripts/ifcfg-br1
DEVICE=br1
ONBOOT=yes
TYPE=Bridge
IPADDR=192.168.1.2
NETMASK=255.255.255.0
GATEWAY=192.168.1.1

* LAN eth1 device:

# cat /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
HWADDR=00:30:48:65:12:b5
ONBOOT=yes
TYPE=Ethernet
BRIDGE=br1

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