Router Recovery when Session is lost:
what if a connexion is lost due to incorrect configuration changes?
what is the best preventive technique nosotros tin dismiss adopt to recover from such situations automatically?
Answer:
"Reload inwards or at"
-an choice to schedule reload therefore that config is reverted as well as connexion is restored.
or:
Seek local help to find console access.
Use 'Reload in' ascendency to schedule 'delay based' reload of device
Use 'Reload at' ascendency to laid fourth dimension equally per clock fourth dimension of your device
Or work 'Reload Cancel' command, inwards example outage does non occur.
Other commands:
sh ip inter brief
sh cdp neighbors
sh users
R2#reload inwards 10
R2#reload cancel
R2#reload at 01:30 23 NOV testing
(remember that the time/clock has to live on assail the router)
###################
Protect your credentials:
What mistakes that most people practise spell creating local access to router or switches?
How to depository fiscal establishment tally whether the password is cleartext, readable or tin dismiss live on decrypted?
What alternatives nosotros tin dismiss work to arrive Secure?
#sh run | i password|secret
#service password-encryption
#enable password ABC
#line console 0
For to a greater extent than safety nosotros should work AAA, Tacacs, Radius.
We tin dismiss also configure the local username password.
#username ak priviledge xv hole-and-corner cisco
#############################
Deep Level Troubleshooting:
Usage of Debug as well as mistakes spell leaving it ON.
How does it affect your operations of Router or Switch?
Does 'debug' ascendency halt when nosotros unopen the window?
-debug ascendency used to analyze packets
- it tin dismiss exhibit the bundle telephone commutation on the telnet or console screen
- debug tin dismiss solely live on stopped using 'undebug all' command, therefore if you lot unopen the window/session, it volition croak along on working inwards the background
Closing the session, doesn't halt the 'debug all' operation!
#debug ip bundle 272
#undebug all
R1#access-list 172 permit ip whatever host 2.2.2.2
R3#ping 2.2.2.2 repeat 1000
R1# volition exhibit that it is denying access
#sh processes cpu history
#############################
#ping 1.1.1.1 beginning 2.2.2.2
#sh ip access-lists
#sh run int e1/0
#sh run int lo0
####################
Chapter 5:
What happens when nosotros run a ascendency which already exists inwards your device?
Does whatever Notification message appear?
Does it overwrite or replace? Yes or No (if not, what volition come about if I run the ascendency therefore take away it).
----
Cisco precisely 'overwrites' the existing amongst ascendency run past times you.
Plan:
1. Log into router as well as run a ascendency that already exists inwards the router
2. We run the same ascendency as well as encounter if whatever message appears or not
3. After that we'll delete the same ascendency as well as therefore encounter if it removes the ascendency from the running config.
Check for existing commands:
#sh run | i ip route
#sh ip route
#sh ip road static
#ip road 0.0.0.0 0.0.0.0 10.1.1.2
#sh ip road 0.0.0.0
#sh log
#sh run | i 0.0.0.0
Fix:
#conf t
#ip road 0.0.0.0 0.0.0.0 10.1.1.2
Test: this ping should reply:
R1#ping 10.0.0.1
Resolution:
Always know what you're going to practise as well as most its impact
Always refer or depository fiscal establishment tally the existing configuration
Review your configuration postal service changes
#################
Chapter 6:
What happens when nosotros practise non capture the session output?
How nosotros tin dismiss practise so?
How to capture a long output inwards i go? i.e. how to alter a page size
Answer:
Whenver nosotros brand changes it is e'er advisable that nosotros accept extra precautions. i.e. regularly salve the config or accept Backup
If past times change, you lot lose connectivity due to some reasons, you lot would non know what changes you lot did
For tape purposes - nosotros must practise it. Also, for sharing the output nosotros tin dismiss brand work of it.
Whever you lot opened upward a example amongst Cisco TAC- they desire to know the output of Certain commands...
Exercise:
We volition logon inwards the router as well as drive to run roughly 10 commands
We'll therefore drive to notice out what ascendency did nosotros come inwards previously
We'll encounter how nosotros tin dismiss capture long outputs inwards i larn - without having to hitting 'enter' every page
-----
#sh ip int brief
Save session output:
Start Putty as well as larn through the settings to salve All Sessions Output, to a .log file.
#terminal length 0
The configuration is picked upward from NVRAM spell Booting upward or Powering On.
Preventive Approach:
Always empathise the critically of your work.
Never assume that zip volition come about or things volition rest adept all time.
Save the config on NVRAM i time operate is finished.
Take the Backup of diverse commands output on your local workstation too.
Make a banknote of what you lot do.
#################
Chapter 7:
what happens when nosotros practise non write or salve the changes on NVRAM?
how nosotros tin dismiss practise so?
Scenario!
- whatever config nosotros make, volition rest inwards 'running configuration'
- nosotros require to commit the changes from run config to startup config
Scenario:
- nosotros accept 2 routers as well as assign them IP addresses, at first, but alter it afterwards
-
R1#int e0/0
#ip add together 10.1.1.2 255.255.255.0
#no shut
#sh ip int brief
R2#int e0/0
#ip add together 10.1.1.12 255.255.255.0
#no shut
#sh ip int brief
---------------------------
- write retentiveness = wr
- re-create running-config startup-config
- if nosotros practise 'sh running-config' as well as compare the result, to the 'sh startup-config' as well as the configs are different, nosotros haven't salve the configuration on the router.
#copy running-config tftp
#copy running-config http
#####################
Chapter 8:
what happens when multiple admins are making changes on a device at the same time? is it possible?
-yes it is possible to brand changes at the same time, as well as if you lot do, you lot volition NOT have notification of this.
how tin dismiss nosotros verify this?
- work 'sh users' to verify if other users are connected to the switch.
Preventine Approach:
Assign the ticket inwards the system, to solely 1 person, to avoid duplicate work.
Check users:
R2#show users
Close the other connection:
R2#clear line of piece of work vty 0
- this volition disconnect the other session
#####################
Chapter 9:
Advertise a novel subnet:
-what are the things to verify earlier advertising whatever network or whatever interface IP address on Layer iii device?
If nosotros practise non verify the existing routing tabular array for the same network which nosotros are going to advertise, therefore at that topographic point would live on loops.
User's legitimate traffic may drop, asymmetric routing may occur, intermittent drops OR consummate outage
- nosotros volition login inwards router3 as well as drive to configure a network which already exists inwards router1
- we'll encounter how it tin dismiss brand things worse
- we'll therefore depository fiscal establishment tally the commands that nosotros should direct keep used earlier advertising a novel subnet
- if you lot ping an IP adress as well as you lot larn dissimilar IP addresses replying to the ping, it agency nosotros direct keep duplicate configs on 2 or to a greater extent than routers/switches
- practise a '#sh ip int brief' to depository fiscal establishment tally IP addresses, to brand certain you lot don't direct keep duplicates
Preventine approach:
Always checking existing routint tabular array using 'show ip road x.x.x.' for whatever network you lot are going to advertise. It may already live on at that topographic point inwards your network!
Do a contrary tracert of the subnet to double depository fiscal establishment tally that it doesn't exist!
Prepare a tape of subnets existence users past times your company! Make an entry amongst your name, date, therefore that no i else starts using the same.
###################
what if a connexion is lost due to incorrect configuration changes?
what is the best preventive technique nosotros tin dismiss adopt to recover from such situations automatically?
Answer:
"Reload inwards or at"
-an choice to schedule reload therefore that config is reverted as well as connexion is restored.
or:
Seek local help to find console access.
Use 'Reload in' ascendency to schedule 'delay based' reload of device
Use 'Reload at' ascendency to laid fourth dimension equally per clock fourth dimension of your device
Or work 'Reload Cancel' command, inwards example outage does non occur.
Other commands:
sh ip inter brief
sh cdp neighbors
sh users
R2#reload inwards 10
R2#reload cancel
R2#reload at 01:30 23 NOV testing
(remember that the time/clock has to live on assail the router)
###################
Protect your credentials:
What mistakes that most people practise spell creating local access to router or switches?
How to depository fiscal establishment tally whether the password is cleartext, readable or tin dismiss live on decrypted?
What alternatives nosotros tin dismiss work to arrive Secure?
#sh run | i password|secret
#service password-encryption
#enable password ABC
#line console 0
For to a greater extent than safety nosotros should work AAA, Tacacs, Radius.
We tin dismiss also configure the local username password.
#username ak priviledge xv hole-and-corner cisco
#############################
Deep Level Troubleshooting:
Usage of Debug as well as mistakes spell leaving it ON.
How does it affect your operations of Router or Switch?
Does 'debug' ascendency halt when nosotros unopen the window?
-debug ascendency used to analyze packets
- it tin dismiss exhibit the bundle telephone commutation on the telnet or console screen
- debug tin dismiss solely live on stopped using 'undebug all' command, therefore if you lot unopen the window/session, it volition croak along on working inwards the background
Closing the session, doesn't halt the 'debug all' operation!
#debug ip bundle 272
#undebug all
R1#access-list 172 permit ip whatever host 2.2.2.2
R3#ping 2.2.2.2 repeat 1000
R1# volition exhibit that it is denying access
#sh processes cpu history
#############################
#ping 1.1.1.1 beginning 2.2.2.2
#sh ip access-lists
#sh run int e1/0
#sh run int lo0
####################
Chapter 5:
What happens when nosotros run a ascendency which already exists inwards your device?
Does whatever Notification message appear?
Does it overwrite or replace? Yes or No (if not, what volition come about if I run the ascendency therefore take away it).
----
Cisco precisely 'overwrites' the existing amongst ascendency run past times you.
Plan:
1. Log into router as well as run a ascendency that already exists inwards the router
2. We run the same ascendency as well as encounter if whatever message appears or not
3. After that we'll delete the same ascendency as well as therefore encounter if it removes the ascendency from the running config.
Check for existing commands:
#sh run | i ip route
#sh ip route
#sh ip road static
#ip road 0.0.0.0 0.0.0.0 10.1.1.2
#sh ip road 0.0.0.0
#sh log
#sh run | i 0.0.0.0
Fix:
#conf t
#ip road 0.0.0.0 0.0.0.0 10.1.1.2
Test: this ping should reply:
R1#ping 10.0.0.1
Resolution:
Always know what you're going to practise as well as most its impact
Always refer or depository fiscal establishment tally the existing configuration
Review your configuration postal service changes
#################
Chapter 6:
What happens when nosotros practise non capture the session output?
How nosotros tin dismiss practise so?
How to capture a long output inwards i go? i.e. how to alter a page size
Answer:
Whenver nosotros brand changes it is e'er advisable that nosotros accept extra precautions. i.e. regularly salve the config or accept Backup
If past times change, you lot lose connectivity due to some reasons, you lot would non know what changes you lot did
For tape purposes - nosotros must practise it. Also, for sharing the output nosotros tin dismiss brand work of it.
Whever you lot opened upward a example amongst Cisco TAC- they desire to know the output of Certain commands...
Exercise:
We volition logon inwards the router as well as drive to run roughly 10 commands
We'll therefore drive to notice out what ascendency did nosotros come inwards previously
We'll encounter how nosotros tin dismiss capture long outputs inwards i larn - without having to hitting 'enter' every page
-----
#sh ip int brief
Save session output:
Start Putty as well as larn through the settings to salve All Sessions Output, to a .log file.
#terminal length 0
The configuration is picked upward from NVRAM spell Booting upward or Powering On.
Preventive Approach:
Always empathise the critically of your work.
Never assume that zip volition come about or things volition rest adept all time.
Save the config on NVRAM i time operate is finished.
Take the Backup of diverse commands output on your local workstation too.
Make a banknote of what you lot do.
#################
Chapter 7:
what happens when nosotros practise non write or salve the changes on NVRAM?
how nosotros tin dismiss practise so?
Scenario!
- whatever config nosotros make, volition rest inwards 'running configuration'
- nosotros require to commit the changes from run config to startup config
Scenario:
- nosotros accept 2 routers as well as assign them IP addresses, at first, but alter it afterwards
-
R1#int e0/0
#ip add together 10.1.1.2 255.255.255.0
#no shut
#sh ip int brief
R2#int e0/0
#ip add together 10.1.1.12 255.255.255.0
#no shut
#sh ip int brief
---------------------------
- write retentiveness = wr
- re-create running-config startup-config
- if nosotros practise 'sh running-config' as well as compare the result, to the 'sh startup-config' as well as the configs are different, nosotros haven't salve the configuration on the router.
#copy running-config tftp
#copy running-config http
#####################
Chapter 8:
what happens when multiple admins are making changes on a device at the same time? is it possible?
-yes it is possible to brand changes at the same time, as well as if you lot do, you lot volition NOT have notification of this.
how tin dismiss nosotros verify this?
- work 'sh users' to verify if other users are connected to the switch.
Preventine Approach:
Assign the ticket inwards the system, to solely 1 person, to avoid duplicate work.
Check users:
R2#show users
Close the other connection:
R2#clear line of piece of work vty 0
- this volition disconnect the other session
#####################
Chapter 9:
Advertise a novel subnet:
-what are the things to verify earlier advertising whatever network or whatever interface IP address on Layer iii device?
If nosotros practise non verify the existing routing tabular array for the same network which nosotros are going to advertise, therefore at that topographic point would live on loops.
User's legitimate traffic may drop, asymmetric routing may occur, intermittent drops OR consummate outage
- nosotros volition login inwards router3 as well as drive to configure a network which already exists inwards router1
- we'll encounter how it tin dismiss brand things worse
- we'll therefore depository fiscal establishment tally the commands that nosotros should direct keep used earlier advertising a novel subnet
- if you lot ping an IP adress as well as you lot larn dissimilar IP addresses replying to the ping, it agency nosotros direct keep duplicate configs on 2 or to a greater extent than routers/switches
- practise a '#sh ip int brief' to depository fiscal establishment tally IP addresses, to brand certain you lot don't direct keep duplicates
Preventine approach:
Always checking existing routint tabular array using 'show ip road x.x.x.' for whatever network you lot are going to advertise. It may already live on at that topographic point inwards your network!
Do a contrary tracert of the subnet to double depository fiscal establishment tally that it doesn't exist!
Prepare a tape of subnets existence users past times your company! Make an entry amongst your name, date, therefore that no i else starts using the same.
###################
