Network Tip No. 12: Configuring an Ethernet/Fast Ethernet Interface

Configuring an Ethernet/Fast Ethernet Interface

Router(config)#int fa0/0	Moves to Fast Ethernet 0/0 interface mode
Router(config-if)#description Sales LAN	Optional descriptor of the link is locally significant
Router(config-if)#ip address 192.168.0.1 255.255.255.0	Assigns address and subnet mask to interface

Network Tip No. 11: Configuring a Serial Interface

Configuring a Serial Interface Router(config)#int s0/0 Moves to interface Serial 0/0 mode Router(config-if)#description Link to ISP Optional descriptor of the link is locally significant Router(config-if)#ip address 192.168.10.1 255.255.255.0 Assigns address and subnet mask to interface Router(config-if)#clock rate 56000 Assigns a clock rate for the interface Router(config-if)#no shut Turns interface on

Network Tip No. 10: Moving Between Interfaces

Moving Between Interfaces Router(config)#int s0 Router(config)#int s0 Moves to interface S0 mode Router(config-if)#exit Router(config-if)#int e0 In int S0, move to E0 Router(config)#int e0 Router(config-if)# In E0 mode now Router(config-if)# Prompt does not change; be careful

Network Tip No. 9: show Commands

show Commands Router#show ? Lists all show commands available Router#show interfaces Displays statistics for all interfaces Router#show interface serial 0 Displays statistics for a specific interface, in this case Serial 0 Router#show ip interface brief Displays a summary of all interfaces, including status and IP address assigned Router#show controllers serial 0 Displays statistics for interface hardware. Statistics display if the clock rate is set and if the cable is DCE, DTE, or not attached Router#show clock Displays time set on device Router#show hosts Displays local host-to-IP address cache. These are the names and addresses of hosts on the network to which you can connect Router#show users Displays all users connected to device Router#show history Displays history of commands used at this edit level Router#show flash Displays info about Flash memory Router#show version Displays info about loaded software version Router#show arp Displays the ARP table Router#show protocols Displays status of configured Layer 3 protocols Router#show startup-config Displays configuration saved in NVRAM Router#show running-config Displays configuration currently running in RAM

Network Tip No. 8: Password Encryption

Password Encryption
Router(config)#service password-encryption
Applies a weak encryption to passwords

Router(config)#enable password cisco
Sets enable password to cisco

Router(config)#line con 0
...

Router(config-line)#password Cisco
Continue setting passwords as above

...

Router(config)#no service password-encryption
Turns off password encryption

Network Tip No. 7: Configuring your Passwords

Configuring Passwords
Works on both routers and switches.

Router(config)#enable password jepoy
Sets enable password


Router(config)#enable secret secret-jepoy
Sets enable secret password


Router(config)#line con 0

Router(config-line)#password console

Router(config-line)#login
Enters console-line mode

Sets console-line mode password to console

Enables password checking at login


Router(config)#line vty 0 4

Router(config-line)#password telnet

Router(config-line)#login
Enters vty line mode for all five vty lines

Sets vty password to telnet

Enables password checking at login


Router(config)#line aux 0

Router(config-line)#password backdoor

Router(config-line)#login
Enters auxiliary line mode

Sets auxiliary line mode password to backdoor

Enables password checking at login

Network Tip No. 6: Configuring a Router Name

Configuring a Router Name This command works on both routers and switches. Router(config)#hostname jepoy Name can be any word you choose jepoy(config)#

Network Tip No. 5: disable Command

disable Command Router#disable Router> Moves you from privileged mode back to user mode

Network Tip No. 4: exit Command

exit Command Router#exit or Router>exit Logs a user off Router(config-if)#exit Router (config)# Moves you back one level Router(config)#exit Router# Moves you back one level

Network Tip No.3: Global Configuration Mode

Router> Limited viewing of config cannot make changes in this mode. Router# Can see config and move to make changes Router#(config) t Router(config)# Moves to global config mode. This prompt indicates that you can start making changes

Network Tip No.2: Enable Command

enable Command

Router>enable Router#	Moves user from user mode to privileged mode

Linux Tip No. 20: Change your Default Gateway

How to Change Your Default Gateway

Temporary
[root@jepoy /]# route add default gw 192.168.1.1 eth0


Permanent

Config file: /etc/sysconfig/network

NETWORKING=yes
HOSTNAME=jepoy
GATEWAY=192.168.1.1

Linux Tip No. 19: View your routing table

[root@proxy ~]# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
203.189.11.64 0.0.0.0 255.255.255.224 U 0 0 0 eth0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
0.0.0.0 203.189.11.65 0.0.0.0 UG 0 0 0 eth0

Linux Tip No. 18: Restart Network Service

[root@proxy docadmin]# /sbin/service network restart
Shutting down interface eth0: [ OK ]
Shutting down interface eth1: [ OK ]
Shutting down loopback interface: [ OK ]
Disabling IPv4 packet forwarding: net.ipv4.ip_forward = 0
[ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: [ OK ]
Bringing up interface eth1: [ OK ]

Linux Tip No. 17: Enable/Disable interface

[root@jepoy]# ifdown eth0
[root@jepoy]# ifup eth0

Linux Tip No. 16 IP Address Aliasing - Permanent

IP Address Aliasing - Permanent

Edit you config file

Config file: /etc/sysconfig/network-scripts/ifcfg-eth0:0

DEVICE=eth0:0
ONBOOT=yes
BOOTPROTO=static
BROADCAST=192.168.10.255
IPADDR=192.168.10.12
NETMASK=255.255.255.0
NETWORK=192.168.10.0
ONBOOT=yes

Linux Tip No.15: IP Address Aliasing - Temporary

Network IP aliasing

ifconfig eth0 XXX.XXX.XXX.XXX netmask 255.255.255.0 broadcast XXX.XXX.XXX.255

route add -host XXX.XXX.XXX.XXX dev eth0

ifconfig eth0:0 192.168.10.12 netmask 255.255.255.0 broadcast 192.168.10.255
ifconfig eth0:1 192.168.10.14 netmask 255.255.255.0 broadcast 192.168.10.255

route add -host 192.168.10.12 dev eth0
route add -host 192.168.10.14 dev eth0

Linux Tip No.14: Locally resolve hosts

Locally resolve hosts

File: /etc/hosts

[root@proxy etc]# more hosts

# Do not remove the following line, or various programs

# that require network functionality will fail.

127.0.0.1 localhost.localdomain localhost

203.189.xxx.xxx proxy.jepoy.net

192.168.0.254 proxy

192.168.0.36 winxp

[root@proxy etc]# ping winxp

PING winxp (192.168.0.36) 56(84) bytes of data.

[root@proxy etc]# ping proxy

PING proxy (192.168.0.254) 56(84) bytes of data.

64 bytes from proxy (192.168.0.254): icmp_seq=0 ttl=64 time=0.092 ms

Linux Tip No.13: Setting your resolver

Setting your resolver – DNS Entries

File: /etc/resolv.conf

search name-of-domain.com - Name of your domain or ISP's domain if using their name server

nameserver XXX.XXX.XXX.XXX - IP address of primary name server

nameserver XXX.XXX.XXX.XXX - IP address of secondary name server

Example:

search jepoy.net

nameserver 203.189.xxx.xxx

nameserver 203.189.xxx.xxx

Linux Tip No. 12: DHCP client configuration

DHCP client configuration

/etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0

ONBOOT=yes

BOOTPROTO=dhcp

Linux Tip No. 11: Changing your IP Address - Permanent

Changing your IP Address – Permanent

Files: /etc/sysconfig/network-scripts/

[root@proxy network-scripts]# ls -l

total 360

-rw-r--r-- 3 root root 190 Feb 28 2007 ifcfg-eth0

-rw-r--r-- 3 root root 191 Nov 8 2005 ifcfg-eth1

-rw-r--r-- 1 root root 254 Jun 21 2001 ifcfg-lo

Pattern:

DEVICE=eth0/eth1/eth3

ONBOOT=yes/no

BOOTPROTO=static/none

IPADDR=xxx.xxx.xxx.xxx

NETMASK=xxx.xxx.xxx.xxx.

GATEWAY=xxx.xxx.xxx

Edit ifcfg-eth0:

/etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0

BOOTPROTO=static

ONBOOT=yes

IPADDR=10.10.10.10

NETMASK=255.255.255.0

GATEWAY=10.10.10.1

Linux Tip No. 10: Changing your IP Address - Temporary

Changing your IP Address - Temporary

Syntax:

Ifconfig netmask

[root@bigboy tmp]# ifconfig eth0 10.0.0.1 netmask 255.255.255.0 up

The ifconfig command does NOT store this information permanently. Upon reboot this information is lost. (Manually add the commands to the end of the file /etc/rc.d/rc.local to execute them upon boot.)