Four campus designs

Answered Question
Mar 15th, 2010

Hi,

Attached please find the best six designs for the discussion (design 11, 12, 15, 16). Below is the description of Data center / DR site and office floor for your reference:

7/F of Data center is meet me room for connecting the fibre cables and core switches

There are 4 server rooms on 15/F to provide IT professional services (PC, printers etc)

5/F is DR site where is another building next to Data center

The bandwidth of all up links / cross links is 10G

Two 3750 are stack together with stacke cable

Assume that there is no costing issue among intra floor fibre cables

1. Which design is better? and why?

2. Some engineer suggest to remove the intra fibre cable (please find the "A" in blue color) between server rooms on 15/F. The network would be more stable. pls advise

rdgs

I have this problem too.
0 votes
Correct Answer by Jon Marshall about 6 years 9 months ago

anitachoi3 wrote:

Hi Jon,

It is the costing issue that cat 4500 may be considered to be core switch in this stage. The whole floor of 15/F would be rented as well. Once the traffic hits to certain level (or figure), the core switch would be upgraded to cat 6xxx serial.

If the intra fibre cables in the same floor are removed. which is the best design from the four design?

rdgs

Anita

"Best" is subjective but i would go with 11.

If you remove the intra fibre cables then 16 becomes like 12. 15 is even worse.

The problem with 12 is that if the 4500 that you have connected the pair of 3750s to fails then that pair of 3750 switches are now isolated from the rest of the network. With 11 you don't have this problem because you have paths to both 4500 switches from each pair of 3750 switches.

Jon

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
Jon Marshall Mon, 03/15/2010 - 09:19

Anita

This is coming very close to paid consultancy type questions.

Some brief points.

1) As Leo and Giuseppe mentioned in a different thread using 10Gbps uplinks to 4500 switches doesn't make a lot of sense. The 4500, even the 4500-E, cannot support that mich throughput and you will get oversubscription. If you want to run a 10Gbps network you should be looking at 6500 switches.

2) Interconnecting your access-layer switch pairs is not a good idea. I think this is what Leo meant by link A. It isn't needed, it makes STP more complex, and you really don't benefit from it.

3) If you are using 3750 switches in the access-layer these are capable of running cross-stack etherchannel as a couple of your proposed designs shows. It would make perfect sense then to go with a 6500 VSS solution instead of the 4500s because

i) throughput as already mentioned

ii) a pair of 6500 switches running VSS are seen as one logical switch which means you can have an etherchannel over both switches so you could have cross-stack etherchannel from each 3750 pair to a pair of 6500 switches running VSS.

Jon

anitachoi3 Mon, 03/15/2010 - 09:24

Hi Jon,

It is the costing issue that cat 4500 may be considered to be core switch in this stage. The whole floor of 15/F would be rented as well. Once the traffic hits to certain level (or figure), the core switch would be upgraded to cat 6xxx serial.

If the intra fibre cables in the same floor are removed. which is the best design from the four design?

rdgs

Correct Answer
Jon Marshall Mon, 03/15/2010 - 09:50

anitachoi3 wrote:

Hi Jon,

It is the costing issue that cat 4500 may be considered to be core switch in this stage. The whole floor of 15/F would be rented as well. Once the traffic hits to certain level (or figure), the core switch would be upgraded to cat 6xxx serial.

If the intra fibre cables in the same floor are removed. which is the best design from the four design?

rdgs

Anita

"Best" is subjective but i would go with 11.

If you remove the intra fibre cables then 16 becomes like 12. 15 is even worse.

The problem with 12 is that if the 4500 that you have connected the pair of 3750s to fails then that pair of 3750 switches are now isolated from the rest of the network. With 11 you don't have this problem because you have paths to both 4500 switches from each pair of 3750 switches.

Jon

anitachoi3 Tue, 03/16/2010 - 07:57

Hi Jon,

Below please find some questions regarding the design 11 for your advise, grateful if you could provide brief description.

The uplink of first stack 3750 switches (e.g. cat3750-1) is connected to first core switch, the uplink of second stack 3750 switches (e.g. cat3750-2) is connected to second core switch.

1. Is flex link configured for both up link? or Is ethernet channel configured for  both up links? which one is better?

2. Regarding Q1, grateful if you could advise the advantage to choose it

3. Regarding Q1, grateful if you could advise on the issue to be consider and aware after Q1 is chosen.

Thank you for your enlighten me on the design

rdgs

Jon Marshall Tue, 03/16/2010 - 08:09

anitachoi3 wrote:

Hi Jon,

Below please find some questions regarding the design 11 for your advise, grateful if you could provide brief description.

The uplink of first stack 3750 switches (e.g. cat3750-1) is connected to first core switch, the uplink of second stack 3750 switches (e.g. cat3750-2) is connected to second core switch.

1. Is flex link configured for both up link? or Is ethernet channel configured for  both up links? which one is better?

2. Regarding Q1, grateful if you could advise the advantage to choose it

3. Regarding Q1, grateful if you could advise on the issue to be consider and aware after Q1 is chosen.

Thank you for your enlighten me on the design

rdgs

Anita

I wasn't thinking of either flex link or etherchannel. If you are only using one uplink per 3750 switch then you can't etherchannel anyway because the etherchannel would need to go to the same 4500 chassis.

If you have multiple vlans per 3750 pair then you can use STP root and secondary settings on the 4500 switches to load-balance the vlan traffic across both uplinks ie. make 4500_1 STP root for odd vlans and 4500_2 STP root for even vlans. That way both uplinks are used. You should then match your HSRP active gateways so 4500_1 is HSRP active for all odd vlans and 4500_2 HSRP active for all even vlans.

Having said that because you are using 4500 switches and 10Gbps connections you may actually be better just using one uplink at a time per pair of 3750 switches for all vlans and then alternate which uplink is used per pair so you balance across the 4500 switches, otherwise you could get problems. I understand cost is an issue but it does then beg the question, as Leo pointed out, why use 10Gbps in the first place.

Flex link i have not used before so i may not be the best person to answer that part.

Jon

anitachoi3 Wed, 03/17/2010 - 09:14

Dear Jon,

Regarding your preceding message "using one uplink at a time per pair of 3750 switches for all vlans and then alternate which uplink is used per pair so you balance across the 4500 switches", grateful if you would re-phase the sentence. I cannot catch the main idea of it.

If there is one link to be activated in design 11, is the design 12 the best?

In design 12, the ethernetchannel can be configured and it could be load balance between two up links. If all up links of server room 1 are down, the traffic may go to server room 2 via the inter fibre cable between the server rooms. Appreciated that you could advise on it.

Thanks

rdgs

Jon Marshall Wed, 03/17/2010 - 11:16

anitachoi3 wrote:

Dear Jon,

Regarding your preceding message "using one uplink at a time per pair of 3750 switches for all vlans and then alternate which uplink is used per pair so you balance across the 4500 switches", grateful if you would re-phase the sentence. I cannot catch the main idea of it.

If there is one link to be activated in design 11, is the design 12 the best?

In design 12, the ethernetchannel can be configured and it could be load balance between two up links. If all up links of server room 1 are down, the traffic may go to server room 2 via the inter fibre cable between the server rooms. Appreciated that you could advise on it.

Thanks

rdgs

Anita

I meant the 2 uplinks, one to each 4500 switch would both be active but only one would be forwarding. The other would be blocked by STP. If the forwarding link failed then the other uplink would be used.

As for design 12, i missed the DR connections which are marked as blocked. Still would use design 11 though because you are complicating something that doesn't need complicating ie. i can't see any benefit from it.

Jon

Leo Laohoo Mon, 03/15/2010 - 14:45

Hi Anita,

When designing a network, follow the KISS Principle:  Keep It Simple, Silly.

Your network is simple but someone decides to make it difficult.  Three and more uplinks can make STP "cranky" even it's being set at default.  I noticed in your diagram that you have specified which ports are blocking so this means someone has to configure the ports or police the behaviour of STP regularly.  And then someone threw in the "A" link. 

I have another option. 

Why not move one of the two 4500 to the DR site instead and remove the 3560-12D?  Each switch stack has an ether-channel link to both. 

I apologize if I'm being thick but if cost is a major factor, why get a core switch that will find difficulty in supporting multiple 10Gb links?   If cost is a major factor, why not use 1Gb?  The Sup6 will not be able to support dual 10Gb links from a 3750 stack.  It's like throwing good money.

anitachoi3 Wed, 03/17/2010 - 09:26

Hi Leo,

Thanks for your proposed design. To rental whole 15 floor would be preferred. So, 90% we may work on the design with 4 server rooms. 1 G up link is also proposed by vendor and it do save the cost. However, the design may not be last longer. From the plan, the 1G up link module and components of core / access switch would be upgraded to 10G within one year (or may be shorter). That's why the 10G could be consider to deploy at the initial stage.

Grateful if Leo could advise on the design 11 and design 12. Thank you very much

rdgs

Leo Laohoo Wed, 03/17/2010 - 15:28

Hi Anita,

1.  I still stand on my initial comment about using 10Gb uplinks to a 4500 chassis.
2.  I still stand on my initial comment about the "A" link.
3.  If 10Gb is really mandatory, I'd go for "11".  I'd recommend using "12" if you have 1Gb uplink.  At either case, "A" link is going to make STP act like a 50 ton gorilla. 
4.  Even if I have money to spend, I don't see any reason (other than bragging rights) to use a 3560E-12D.  I'd still recommend relocating one of the 4500 down from the 7/F to the 5/F.  Now THAT makes true redundancy.  A close mirror-image of your network.

Once you (and only you) have made a decision, please don't let anyone muddle things up.  It will only stress you out and delay the implementation of the project.

In my humble opinion, the most difficult part is the fibre optic cabling.  The good part is that both 1Gb and 10Gb uses the same link - you just need to change the modules.  If the company goes down the 4500 avenue with the thought of future upgrade to the 6500 ... gee whiz.  I don't envy the financial officer.  This is one tough banana to convince upper managment you purchase an expensive 4500 as an "interim" and then you buy the 6500.  Wow!  Mindboggling and awesome!

Leo Laohoo Wed, 03/17/2010 - 19:08

Hi Anita,


Can I throw some info to sow confusion?


Cisco Catalyst 3750-X and 3560-X Series Switches Data Sheet
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/data_sheet_c78-584733.html


Cisco Catalyst 2960-S and 2960 Series Switches with LAN Base Software
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/product_data_sheet0900aecd80322c0c.html


The new 2960S now offers 10Gb uplinks.  The new 3750-X and 3560-X Series Switches offer either hot-swappable between a choice of either 1Gb SFP OR 10Gb SFP.


If you want redundancy, look at the 3750-X and 3560-X StackPower redundancy.  Perfect timing, don't you think?


You can order the 2960S, 3560X and 3750X.  First shipment starts mid-April for the 2960S and mid-May for the rest.

Actions

This Discussion