Archive for category Networking

Reducing TIME_WAIT sockets in Nginx and Apache

Edit /etc/sysctl.conf and add

# Enables fast recycling of TIME_WAIT sockets.
# (Use with caution according to the kernel documentation!)
net.ipv4.tcp_tw_recycle = 1

# Allow reuse of sockets in TIME_WAIT state for new connections
# only when it is safe from the network stack’s perspective.
net.ipv4.tcp_tw_reuse = 1

After this run in terminal

sysctl -p




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Changing 2G mode to 3G mode

This command is based on Huawei spec:
AT^SYSCFG Huawey command reference

To see the supported values, you can query your own modem sending the “AT^SYSCFG=?” command.

13=GSM only
14=WCDMA only
16=no Change

1=GSM prefered
2=WCDMA prefered
3=no Change

3fffffff = All
other (query list with “AT^SYSCFG=?”)

0=Not Supported
2=no Change

0=Circuit-Switched only
1=Packet-Switched only
2=Circuit- & Packet-Switched
4=no Change

^SYSCFG:(2,13,14,16),(0-3),((80000,”GSM850″),(200000,”GSM1900″),(400380,”GSM900/GSM1800/WCDMA2100″),(4a80000,”GSM850/GSM1900/WCDMA850/WCDMA1900″),(3fffffff,”All Bands”)),(0-2),(0-4)

You can find more at:

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Problem to send email hotmail

Hotmail has some weird policy, if you have any problem sending email from your ISP to domain, please read this:


Good luck!

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World Cable Maps

Cool site, showing some of the most important cables/fiber/backbones in the world

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Linux Wake on Lan

Check if your interface has support and if the BIOS configuration is OK.

ethtool ethx | grep -i 'support'

hamilton@saygon:~$ sudo ethtool eth0 | grep -i 'support'
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
Supports auto-negotiation: Yes
Supports Wake-on: pumbg

Available options  are:

wol p|u|m|b|a|g|s|d...
Sets Wake-on-LAN options. Not all devices support this. The argument to this option is a string of characters specifying which options to enable.
p Wake on phy activity
u Wake on unicast messages
m Wake on multicast messages
b Wake on broadcast messages
a Wake on ARP
g Wake on MagicPacket(tm)
s Enable SecureOn(tm) password for MagicPacket(tm)
d Disable (wake on nothing). This option clears all previous options.

If "g" option is not ok, please run:

ethtool -s eth0 wol g

Get your MAC addrees before rebooting:

hamilton@saygon:~$ ifconfig | grep HWaddr
eth0      Link encap:Ethernet  HWaddr 00:1c:c0:c3:ed:fd  

To wake your PC, make sure that you are running this command from another PC inside the same network

etherwake 00:1c:c0:c3:ed:fd

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Cisco Console Cable

RJ45 -> DB9 F
1 -> 8
2 -> 9
30 -> 2
4 -> 5
6 -> 3
7 -> 4
8 -> 7

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CrossOver cat 5 “Gigabit” cable pinout

Pin Connector #1  Connector #2
1 white/orange     white/green
2 orange                green
3 white/green       white/orange
4 blue                    white/brown
5 white/blue         brown
6 green                  orange
7 white/brown     blue
8 brown                white/blue

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