list all NM connections: nmcli con
start connection (wifi, vpn, etc): nmcli con up id ConnectionName
down connection: nmcli con down id ConnectionName
command line controlling NetworkManager
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Category Archives: Linux networking
VPN PPTP Client
yum install pptp
vi /etc/ppp/chap-secrets
my_username vpn.linux4yyou.tk “my_password” *
[username][space][server name][space][password][space][ip address allowed]
vi /etc/ppp/peers/vpn.linux4yyou.tk
pty “pptp vpn.linux4yyou.tk –nolaunchpppd”
name my_username
remotename vpn.linux4yyou.tk
require-mppe-128
file /etc/ppp/options.pptp
ipparam vpn.linux4yyou.tk
modprobe ppp_mppe
vi /etc/ppp/options.pptp
lock
noauth
refuse-pap
refuse-eap
refuse-chap
nobsdcomp
nodeflate
require-mppe-128
pppd call vpn.linux4yyou.tk
ip a | grep ppp
tail -f /var/log/message | grep ppp
delete a static ARP entry from local ARP table
arp -d 10.0.0.2
igb eth0 reset adapter
cd /tmp
curl “http://downloads.sourceforge.net/project/e1000/igb%20stable/5.1.2/igb-5.1.2.tar.gz?r=http%3A%2F%2Fsourceforge.net%2Fprojects%2Fe1000%2Ffiles%2Figb%2520stable%2F5.1.2%2Figb-5.1.2.tar.gz%2Fdownload&ts=1392823683&use_mirror=superb-dca2” [^]
tar xzvf igb-5.1.2.tar.gz -C /usr/local/src
cd /usr/local/src/igb-5.1.2/src
yum install kernel-devel
make install
rmmod igb; modprobe igb
NSX
Programmatically create, provision, snapshot, delete and restore complex networks all in software. VMware NSX™ breaks through current physical network barriers, enabling data center operators to achieve order of magnitude better speed, economics and choice.
iptables change default policy
iptables -P INPUT DROP or iptables -P INPUT ACCEPT
error in ifcfg-eth0-range0: IPADDR_START and IPADDR_END don’t agree
You should check if IPADDR_START or IPADDR_END syntax is correct maybe its misplaced.
Cat6 cable
Cat6 cables, also called Category 6 or Cat 6 cables, provide lower crosstalk, a higher signal-to-noise ratio, and are suitable for 10GBASE-T (10-Gigabit Ethernet), while Cat5e cables support only up to 1000BASE-T (Gigabit Ethernet).
As a means of future-proofing your network, Cat6 is generally a better choice and worth the small premium in price. Cat5e and Cat6 cables are both backwards compatible, which means newer Cat6 cables can be used with older Cat5e, Cat5 and even Cat3 equipment.
slow RD (remote desktop) connection
Fix.
netsh interface tcp set global autotuninglevel=disabled
and
netsh interface tcp set global autotuninglevel=highlyrestricted
monitor packet loss percentage icmp
/bin/ping -q -n -c 10 linux4you.tk | /bin/grep “packet loss” | /usr/bin/cut -d ” ” -f 6 | /usr/bin/cut -d “%” -f1
Error: Unable to read database “/var/lib/vnstat/venet0
yum install vnstat
if you do something like this:
vnstat -u -i venet0
you can get error:
Error: Unable to read database “/var/lib/vnstat/venet0”.
Info: -> A new database has been created
so:
you should wait a bit and again run:
/usr/bin/vnstat -u -i venet0
vnstat -d
add comment to your iptables rule
iptables -A ….. -m comment –comment “${comment}” -j REQUIRED_ACTION
NFS shared file system
mkdir /dba
Add the following lines to the /etc/exports file.
/dba *(rw,sync,no_wdelay,insecure_locks,no_root_squash)
Run the following command to export the NFS shares.
chkconfig nfs on
service nfs restart
Log into another server and mount the the NFS share:
Add the following lines to the /etc/fstab file:
nfs_server:/dba /home/oracle nfs rw,bg,hard,nointr,tcp,vers=3,timeo=300,rsize=32768,wsize=32768,actimeo=0 0 0
chown -R oracle:oinstall /home/oracle
redirecting network traffic to a new IP using iptables
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A PREROUTING -p tcp –dport 80 -j DNAT –to-destination xx.xx.xx.xx:80
iptables -t nat -A POSTROUTING -j MASQUERADE
limit apache connections per second
iptables -A INPUT -p TCP –dport 80 –syn -m recent –name http –update –seconds 60 –hitcount 5 -j REJECT
iptables -A INPUT -p TCP –dport 80 –syn -m recent –name http –set
it will prevent someone making more than 5 connections in 60 seconds on port 80