Part VII – Network Management
Router Boot Sequence:
Router performs POST and verify that all components
of the device are operational and present.
The bootstrap looks for and loads the Cisco IOS
file. By default, the IOS is loaded from flash memory.
The startup-config file is loaded and ran, or the
router will go in setup mode if no startup-config file is present.
Configuration Register: all Cisco routers have a
16-bit software register stored in NVRAM.
Bits
|
Description
|
Bits
|
Description
|
0-3
|
Boot Field: 00 –
ROM Monitor, 01 – Boot Image from ROM
02-F – Use boot
commands in NVRAM
|
11-12
|
Console line speed
|
6
|
Ignore NVRAM
contents
|
13
|
Boot default ROM
software if network boot fail
|
7
|
OEM Bit enabled
|
14
|
IP broadcasts do
not have net numbers
|
8
|
Break disabled
|
15
|
Enable diagnostic
messages and ignore NVRAM content
|
10
|
IP Broadcast with
all Zero
|
The configuration register can be viewed with sh
version and be changed with (config)#config-register 0xvalue
where value is a 4 digit hex number. If you need to interrupt the boot sequence by performing a break to change the configuration register and enter privilege dmode,
use romon 1>confreg 0xvalue followed by reset on a Cisco 2600 and o/r 0xvalue followed by i on a Cisco 2500.
where value is a 4 digit hex number. If you need to interrupt the boot sequence by performing a break to change the configuration register and enter privilege dmode,
use romon 1>confreg 0xvalue followed by reset on a Cisco 2600 and o/r 0xvalue followed by i on a Cisco 2500.
sh flash:
displays the content and space available of Flash memory.
copy (flash tftp)/(tftp
flash): used to backup or restore the IOS to or from a tftp server.
Requires a default directory on the tftp server to work.
copy (run/start
tftp)/(tftp run/start): used to backup or restore the running
or startup config files. Each ! represent 1 UDP segment transmitted.
erase startup-config:
erases the startup config file. The router will boot in setup mode the next
time unless another startup config file is created.
config network:
copy the config file from a TFTP server into RAM.
tftp server system imagename:
used to configure a router as a tftp server that will be able to send the IOS
to another router.
CDP
(Cisco
Discovery Protocol): protocol that gathers hardware and protocol information
about neighbour devices for troubleshooting and documenting the network. The
CDP timer specifies how often the CDP packets are sent, and the CDP holdtime
is the duration the device will hold packets received from neighbour
devices.
sh cdp [(neighbor
[detail])]: displays the content of both timers or (neighbour)
displays the information gathered about neighbour devices (hostname, interface
packet is received on, capability, platform, interface from which the packet
was broadcasted from and holdtime). The detail command will also display
the IP address, protocols and IOS version of neighbouring devices (equivalent
to sh cdp entry *)
(config)#cdp timer/holdtime number:
used to change the value of either timer, which are defaulted to 60 and 180
seconds.
sh cdp traffic:
outputs the number of packets sent and received and eventual errors with CDP.
sh cdp interface:
shows the CDP status on router interface or switch port.
clear cdp table:
clears the CDP table of information gathered about the neighbouring devices.
(config)#no cdp run: disable CDP for the
whole router/switch.
(config-if)#[no] cdp enable: disable
or enable CDP on a specific interface.
Telnet: once the VTY line password is set, you can
telnet into a device. To switch from the remote connection to the local prompt,
use the Ctrl+Shift+6 key followed by X.
sh sessions:
shows connections made to remote devices. The last session identified with a
star can be returned to by pressing the enter key twice.
sh users:
shows a list of users connected to your device. The * represent the session
used to enter the command.
exit: to end the
telnet session.
disconnect number:
to close the telnet session number from the local console
clear line number: to terminate a connection from a remote host.
Resolving host names: it is possible to configure routers to store a host name table and use a DNS service.
(config)#ip host name address: adds an entry
in the host table (use no ip host name to remove).
#sh hosts: displays the host table. The perm
flag indicates a manual entry in the table, and the temp flag
indicates an entry solved by DNS.
To configure a DNS server:
(config)#[no] ip domain-lookup: use no
to disable. This is turned on by default.
(config)#ip name-server address (Maximum
of 6 DNS server addresses)
(config#)[ip domain-name name]: Optional
command that appends the domain name to the host name typed in.
No comments:
Post a Comment