CCNP Certification / BCMSN Exam Tutorial: HSRP MAC Addresses And Timers
Computer and Technology - To earn your CCNP certification and pass the BCMSN exam, you have to understand what HSRP does and also the many configurable options. As the operation of HSRP is fairly simple (and covered in a previous tutorial ), you also have to know how HSRP arrives in the MAC address to the virtual router - along with how you can configure a brand new MAC for that virtual router. This puts us in the unusual position of making a physical address for any router that does not exist!
The output of show standby for any two-router HSRP configuration is shown below.
R2#show standby
Ethernet0 - Group 5
Local state is Standby, priority 100
Hello time 3 sec, hold time 10 sec
Next hello sent in 0. 776
The virtual IP address is 172. 12. 23. 10 configured
Active router is 172. 12. 23. 3, priority 100 expires in 9. 568
Standby router is local
One state changes, last state change 00: 00: 22
R3#show standby
Ethernet0 - Group 5
Local state is Active, priority 100
Hello time 3 sec, hold time 10 sec
Next hello sent in 2. 592
The virtual IP address is 172. 12. 23. 10 configured
Active router is local
Standby router is 172. 12. 23. 2 expires in 8. 020
Virtual mac address is 0000. 0c07. ac05
Two state changes, last state change 00: 02: 08
R3 is in the Active state, while R2 is in Standby. The hosts are by using the 172. 12. 123. 10 address as their gateway, but R3 is handling the workload. R2 will require over if R3 becomes unavailable.
An IP address was assigned towards the virtual router throughout the HSRP configuration process, although not a MAC address. However, there‘s a MAC address beneath the show standby output on R3, the active router. How did the HSRP process arrive with a MAC of 00-00-0c-07-ac-05?
Well, a lot of the work is already done until the configuration is even begun. The MAC address 00-00-0c-07-ac-xx is reserved for HSRP, and xx is that the group number in hexadecimal. That is a very good skill to possess to the exam, so ensure you are comfortable with hex conversions. The group number is 5, and that is expressed as 05 having a two-bit hex character. When the group number was 17, we'd see 11 at the conclusion of the MAC address - one unit of 16, one unit of 1.
The output from the show standby command also tells us the HSRP speakers are sending Hellos every 3 seconds, having a 10-second hold time. These values could be changed using the standby command, but HSRP speakers inside the same group should have similar timers. You may also tie through hello time for them to the millisecond, but it is doubtful you will ever get to do this.
R3 (config-if ) #standby 5 timers?
1-254 Hello interval in seconds
msec Specify hello interval in milliseconds
R3 (config-if ) #standby 5 timers 4?
5-255 Hold amount of in time seconds
R3 (config-if ) #standby 5 timers 4 12
Another important HSRP skill is knowing how you can affect the Active router assignment. I am going to show you how you can do this, and how you can configure HSRP interface tracking, in a subsequent section of my CCNP / BCMSN exam tutorial!
I think it's enough all about CCNP Certification / BCMSN Exam Tutorial: HSRP MAC Addresses And Timers. Thanks so much :)
CCNP Certification / BCMSN Exam Tutorial: HSRP MAC Addresses And Timers
The output of show standby for any two-router HSRP configuration is shown below.
R2#show standby
Ethernet0 - Group 5
Local state is Standby, priority 100
Hello time 3 sec, hold time 10 sec
Next hello sent in 0. 776
The virtual IP address is 172. 12. 23. 10 configured
Active router is 172. 12. 23. 3, priority 100 expires in 9. 568
Standby router is local
One state changes, last state change 00: 00: 22
R3#show standby
Ethernet0 - Group 5
Local state is Active, priority 100
Hello time 3 sec, hold time 10 sec
Next hello sent in 2. 592
The virtual IP address is 172. 12. 23. 10 configured
Active router is local
Standby router is 172. 12. 23. 2 expires in 8. 020
Virtual mac address is 0000. 0c07. ac05
Two state changes, last state change 00: 02: 08
R3 is in the Active state, while R2 is in Standby. The hosts are by using the 172. 12. 123. 10 address as their gateway, but R3 is handling the workload. R2 will require over if R3 becomes unavailable.
An IP address was assigned towards the virtual router throughout the HSRP configuration process, although not a MAC address. However, there‘s a MAC address beneath the show standby output on R3, the active router. How did the HSRP process arrive with a MAC of 00-00-0c-07-ac-05?
Well, a lot of the work is already done until the configuration is even begun. The MAC address 00-00-0c-07-ac-xx is reserved for HSRP, and xx is that the group number in hexadecimal. That is a very good skill to possess to the exam, so ensure you are comfortable with hex conversions. The group number is 5, and that is expressed as 05 having a two-bit hex character. When the group number was 17, we'd see 11 at the conclusion of the MAC address - one unit of 16, one unit of 1.
The output from the show standby command also tells us the HSRP speakers are sending Hellos every 3 seconds, having a 10-second hold time. These values could be changed using the standby command, but HSRP speakers inside the same group should have similar timers. You may also tie through hello time for them to the millisecond, but it is doubtful you will ever get to do this.
R3 (config-if ) #standby 5 timers?
1-254 Hello interval in seconds
msec Specify hello interval in milliseconds
R3 (config-if ) #standby 5 timers 4?
5-255 Hold amount of in time seconds
R3 (config-if ) #standby 5 timers 4 12
Another important HSRP skill is knowing how you can affect the Active router assignment. I am going to show you how you can do this, and how you can configure HSRP interface tracking, in a subsequent section of my CCNP / BCMSN exam tutorial!
I think it's enough all about CCNP Certification / BCMSN Exam Tutorial: HSRP MAC Addresses And Timers. Thanks so much :)
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