Cisco 3750 Real World Notes:

Best resource for Cisco 3750 stacking configuration: http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00807811ad.shtml

1. The Master switch in a stack is the single point of management for the entire stack, from the master you can configure global configs that apply to the all the stack members.

2. All Stack members are eligible to be elected as stack masters if the stack master goes down or becomes unavailable.

3. When a stack member goes down the remaining switches begin the electing process from themselves.

4. Priority value determines the Master switch in a stack. The priority value can be 1 to 15. The default priority value is 1. Cisco recommends that you assign the highest priority value to the switch that you prefer to be the stack master. In this example, the master switch has a priority value of 15.

3750#show switch detail

Current

Switch# Role Mac Address Priority State

--------------------------------------------------------

1 Slave 000c.30ae.4f00 9 Ready

*2 Master 000d.bd5c.1680 15 Ready

5. After the IOS upgrade, any one or more of the switches do not boot with the new images. Or, when you add a switch to the existing stack and the newly added switch has a different Cisco IOS software release than the existing switch stack, the new switch is unusable. The 3750 switch stack has a feature called auto-upgrade which is enabled by default. This feature enables the switch stack to automatically upgrade the IOS on the newly added switch. Sometimes this auto-upgrade fails to upgrade the IOS of the newly added switch.

6. A switch stack has up to nine stack members connected through their StackWise ports. A switch stack always has one stack master.

7. To add a switch, as a master, to a stack, complete these steps:

Note: Make sure the switch you add into the stack has the same IOS version as the switches in the stack

.

1. Issue the show switch command.to gets the priority value of the members of the stack.

3750-Stk>show switch

Current

Switch# Role Mac Address Priority State

--------------------------------------------------------

1 Slave 0016.4748.dc80 1 Ready

*2 Master 0016.9d59.db00 5 Ready

2. Change the priority value of the switch to be added to a value greater than the highest priority of the stack. In the illustration, the priority value has to be a value of more than "5.".

switch stack-member-number priority new-priority-value

3. Make sure that the stack is fully connected so that, when you connect the new switch, the stack will be at least in half connectivity, and do not partition.
4. With the new switch powered on, connect the StackWise ports of the switch to the stack.
5. The election for the stack master occurs, and the new switch will be elected as the master since it has the highest priority value.
6. The members of the previous stack will reboot themselves to join the new stack. After all the members come up, issue the command show switch to verify stack membership.

Real World Cisco 3750 Stack commands to know:

Switch# show switch - You can display the stack member

Switch(Config)#switch (current-stack-member-number) renumber (new-stack-member-number)

You can manually change the stack member number by using the above global configuration command.The new number goes into effect after that stack member resets.

Switch# reload slot (stack-member-number) - A single switch can be reset in the stack by using the privileged EXEC command

Switch(Config)# switch (stack-member-number) priority (new-priority-value) - You can change the priority value for a stack member by using the global configuration command:

remote command (stack-member-number) show version - To run a command (such as show version) on a single switch in the stack:

Valid values for stack-member-number are 1-9

There is alot more to Cisco 3750, but this should help do basic switch status checks and configuration. Most of the above came directly from www.cisco.com. I just posted the items most relevent.

thanks
JC

Setting Up a New Network, reviewing the gear

Check out the video, its not the best quality because I used my Blackberry Bold to record it. But at least you get to see the gear being used to setup a new network. You get to see the Cisco ASA 5505, which is awesome. These Security appliances, are great for there small footprint. They are really designed for a small to medium branch office network. It has many of the features that the Cisco 5510 or 5520 have, just smaller and more compact.

Also in this network we are using cisco 3750 stackwise switches for the core/distro layer. For those that don't know, Cisco design model includes Access layer, distro and core layer.

The access is where you typically have the users connect to, or the closet switches. The Distribution layer is where we configure network policies, and restrictions. The core should be the fastest part of the network. It typically is the backbone. In this network the 3750 is combo core/distro and our access layer will be Cisco 3560 with POE or power over ethernet. This means when we plug in an access point or phone that requires power. The device is powered up just by plugging into a POE port. Very kewl!!!

The best part of the video is understanding how kewl the Cisco 3750 switches are. In real world these switches allow us to start small and grow slowly, or scale as needed.

Review of Real World:
- 3750 use stackwise cables as the backplane so that the entire stack is managed as a single switch. Very cool, configure master and then the rest act as part of one large switch.
- Always power up the switch you want to be the master first. Then check the led to show that the switch is in fact elected as master.
- Once the master is elected, then power on the rest of the switches on the stack.
- Its probably a good idea to configure the master priority so that the switch you want master always boots up as master. I will put the config for this in the next post.
- The best thing about this stack wise is that you can add switches to the stack when you need more ports.

The bad news about Master election:
- If you use auto election, then if you power off the stack and boot up switches in different order, you will find that the switch orginally configured as master will likely not be the master. This will affect how the ports show when you run the "sho int status" command. What used to be gi1/0/1 will not be the same if the master changes. Solution to this is hardcode the master in the config.
- The other bad news, is make sure when you add a switch the stack, that the switch code is the same as the other switches in the stack, if not the newer code switch will want to become the master. This in turn can cause all kinds of problems in a production environment.
- simple rules, use same switch series 3750, same code or make sure they are all up to latest code before implementing new switch. Make sure that you hardcode a master to avoid issues upon unexpected reboots or power outages. (Although they should be on UPS, stuff always happens).

Introducing " JC'S Real World Cisco Blog"

Welcome to my blog, I am very excited to be able to share with anyone interested in learning Cisco networking technologies. Anything I learn on the field or stuff that I am working on, I will share on this blog. I also encourage others to post their knowledge.

Why this blog? Well I know how hard it is to get into the Cisco Networking field. I know when I started, it was hard. There is so much to learn and sometimes no one to help out. Getting a CCNA is great but it does not give the entire real world you need to actually do the job.

Also the CCNA schools and labs out there utilize old outdated equipment for training. I want to provide videos and documentation covering updated gear, and basic “how to” training.

Many of you will know IT stuff and least I hope you do. But if no, no worries if you don’t. But if you know Windows or computer repair, you know that what makes a top notch tech standout is the secret tools of the trade that you only learn in the field and not in some A+ classroom or MCSE seminar. Therefore another goal of this blog is to provide those types of tools for Cisco Engineers.

Please understand that I encourage certifications and I will post cert stuff too. I am CCNA, A+, Network+ and many more to list. I teach the A+ and Network+ at a local training institution. So please get your certs, it helps to get the job and get the needed foundation.

In conclusion, feel free to post questions, topics and your own knowledge. I still have lots to learn in the Cisco field too and want to learn from others.

Thanks for visiting.

Jonathan Cabrera