So test drove CentOS 6 Minimum install ..
Only real hiccup till now is :
TUV ( the upstream vendor) aka RHEL decided to disable the network interfaces by default. WTF to that.
A glance at the FAQ will show the solution :
Here’s my version for multiple interfaces.
# cd /etc/sysconfig/network-scripts/
# sed -i -e ‘s@^ONBOOT=”no@ONBOOT=”yes@’ ifcfg-eth*
Installing SNMP daemon and tools:
As root
yum -y install net-snmp.i686
yum -y install net-snmp-utils
Once these are installed start the snmp daemon:
/etc/init.d/snmpd start
chkconfig snmpd on
This is just the basic install but testing it :
snmpwalk -v 1 -c public -O e 127.0.0.1
For production servers it is advisable to at least change the community name.
All configs are in
/etc/snmp/snmpd.conf
and traps are setup here:
/etc/snmp/snmptrapd.conf
No traps are set by default.
Enjoy !!
#vim /etc/sysconfig/network
Use something like
HOSTNAME=testarossa.maranello.local
to overwrite the default name and domain of the server.
e.g.
NETWORKING=yes HOSTNAME=testarossa.maranello.local
To avoid rebooting issue the following :
hostname testarossa.maranello.local
That will set it for the current session.
To monitor TCP and UDP connections the following command is very useful:
netstat -t -u
to have a continuous update use the watch command:
watch netstat -t -u
There is a much stronger tool for real time analysis called iptraf.
It is quite self explanatory :
at command line run
iptraf
This tool has many functions and is text mode menu ncurses based application really worth learning.
The following three commands display the current routing table:
# route
Output:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.1.0 * 255.255.255.0 U 0 0 0 ra0 default dsl-router 0.0.0.0 UG 0 0 0 ra0
# /sbin/route
Output:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 191.255.255.0 * 255.255.255.0 U 0 0 0 eth0 169.254.0.0 * 255.255.0.0 U 0 0 0 eth0 default 191.255.255.1 0.0.0.0 UG 0 0 0 eth0
You can use -n option, to display numerical addresses instead of trying to determine symbolic host names (via dns or /etc/hosts file). This is useful if you are trying to determine why the route to your nameserver has vanished.$
#/sbin/route -n
Output:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 191.255.255.0 0.0.0.0 255.255.255.0 U 0 0 0 venet0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 venet0 0.0.0.0 191.255.255.1 0.0.0.0 UG 0 0 0 venet0
Please note that a destionation entry 0.0.0.0 (or default) is the default gatway. In above example 191.255.255.1 is a default gatway.
The syntax is as follows:
route add default gw {IP-ADDRESS} {INTERFACE-NAME}
Where,
For example if your router IP address is 192.168.1.254 type the following command as the root user:
# route add default gw 192.168.1.254 eth0
OR use hostname such as dsl-router:
# route add default gw dsl-router eth0
If you find above command hard to use, consider using GUI tools. If your are using Red Hat/CentOS/Fedora core Linux type following command:
# redhat-config-network
OR
If you are using other Linux distribution use command:
# network-admin
Total-addresses: how many unique addresses can be represented. To determine how many are available to be assigned to devices you need to subtract 2 from the provided number to allow for the ‘network’ and ‘broadcast’ address. A further one of these may need to be assigned to a router.
eg: 192.168.1.0/25 would include all address between 192.168.1.0 and 192.168.1.127. eg: 192.168.1.128/25 would include all address between 192.168.1.128 and 192.168.1.255 |
