How To Configure NetFlow On A Cisco Router

Recently I was wondering what was the best way to analyze and monitor the traffic that passes the routers between sites \ offices.


After researching the issue I found out the Cisco NetFlow protocol allows you to analyze the traffic that pass the router,  however In order to get this done we need to

Configure our routers to do a few things:


1.       Install Software that analyze NetFlow

2.       Enable NetFlow on the router

3.       Configure the router to send the logs to a netflow analyzer server (needs to be configure before)


Once you got the server or PC up and running with a netflow software (there are a lot of free application, I used Manage Engine NetFlow Analyzer 6 which allows you to monitor 2 router for free) , We need to tell the router to send the NetFlow logs to the server, To do that here is the commands we need to type:



Router(config)# ip flow-export destination {hostname|ip_address} 9996    

Router(config)#  ip flow-export source {interface} {interface_number}    

Router(config)#ip flow-export version 5                        

Router(config)#  ip flow-export version 5

Router(config)#  ip flow-cache timeout inactive 15

Router(config)#  snmp-server ifindex persist



To monitor and Check that we configured the Router to send the logs type:


Router# show ip flow export

Router#   show ip cache flow

Router#  show ip cache verbose flow



Configuration Sample:


router#configure terminal
router(config)#interface FastEthernet 0/1
router(config-if)#ip route-cache flow
router(config)#ip flow-export destination 9996
router(config)#ip flow-export source FastEthernet 0/1
router(config)#ip flow-export version 5
router(config)#ip flow-cache timeout active 1
router(config)#ip flow-cache timeout inactive 15
router(config)#snmp-server ifindex persist

router# copy run start
router#show ip flow export
router#show ip cache flow




To Cancel NetFlow:


no ip flow-export destination {hostname|ip_address} {port_number}

no ip route-cache flow



How To Apply QoS For VOIP With Cisco Routers Between Two Sites

After a few days of searching the Internet for a simple template and example of VOIP QoS implamntation  without any results I have decided to write KB on how to implement VOIP Q0S on a Cisco router between  two offices \ sites.

This example is ready to use however you need to find which protocol your VoIp telephone system is using (in this example i used MITEL 3000)

once you find it all you have to do is fill it in and paste the code to to both routers.

If you happy with the policy map names leave it as it is, and don’t forget to apply the policy to the right interface.

The commands with explanations:


class-map match-all Voice
 match ip dscp 46                           —- Remember to put the right protocol number. (46 is for MITEL)

class-map match-all signalling     — this name can be change
match ip dscp 26                           —- Remember to put the right protocol number. (26 is for MITEL)

policy-map voip                            — this name can be change
class Voice                                    — this name need to match class-map match-all
bandwidth percent 30                   —  percent for voice
class signalling                            — this name need to match class-map match-all�
bandwidth percent 5                    ——  percent for signalling
class class-default

interface gi0/1                             —- Apply Policy Map to Interface
service-policy output Voip

To monitor the traffic and see that everything is working type:
show policy-map interface gi0/0
The commands without  explanations and ready to be copied:

class-map match-all Voice
 match ip dscp 46

class-map match-all signalling
match ip dscp 26

policy-map voip
class Voice
bandwidth percent 30
class signalling
bandwidth percent 8
class class-default
interface gi0/1
service-policy output Voip

Configure \ Enable SNMP On A Cisco Router Or Switch

In order for to Monitor a Cisco Router or Switch using SMNP with a 3rd party software like MTRG we need to enable SNMP on the device and set a SNMP String.

To do it follow the steps below:

Log in to the router and enter configuration mode:

Router#configure terminal

Enable SMNP:

Router(config)#snmp-server community public RO
Router(config)#snmp-server community private RW

Then save the changes:

Router#write memory

View SNMP command :

Router# sh snmp
Chassis: FHK1215F41P
2411 SNMP packets input
    0 Bad SNMP version errors
    0 Unknown community name
    0 Illegal operation for community name supplied
    0 Encoding errors
    2819 Number of requested variables
    0 Number of altered variables
    178 Get-request PDUs
    2233 Get-next PDUs
    0 Set-request PDUs
    0 Input queue packet drops (Maximum queue size 1000)
2411 SNMP packets output
    0 Too big errors (Maximum packet size 1500)
    18 No such name errors
    0 Bad values errors
    0 General errors
    2411 Response PDUs
    0 Trap PDUs

To Remove \ Disable SNMP

Router(config)#no snmp-server community public RO
Router(config)#no snmp-server community private RW