CAN ANY ONE EXPLAIN ME PLEASE

[Syed Aman Hussain]

HI ALL,

     AND Thanks in Advance,,

in my network we have one core Switch 6509 and 17 Catalyst 3750-48ports  Switches,  devided by floor wise with the fiber connections  only single link in each floor we have 3 switches with stacking and two floor only one switch,we are using 172.16.0.0 /16 subnets , we have 30 serves, some of the servers are connected with access switch and remaining servers are connected with Core switch, and we have around 800 users , all the switches are working in default vlan, which is vlan 1,

now i want to re-engineering the network ,

as floor wise i want to assign vlan , will it increase the network proformence ,,

or i have to change the ip addressing scheme form /16 to /24

explain me can implementing vlan increase the proformence of the network,,

Thanks and Regards

Aman

[Kevin Dorrell]

That is a lot of machines on a single VLAN. Have you ever tried putting a network monitor on a switchport and seeing how many broadcasts (and multicasts) you have per second as background noise? Then just think that every machine has to process every one of those broadcasts. If you get any problems of the network such as loops, the situation will be even worse.

If you divide that broadcast domain up into smaller parts, then the problem is alleviated. Each machine has to listen to the background noise only from the the machines in its own VLAN. My guess is that there will be an improvement. Even better, if you get any layer-2 problems, they will be limited to one VLAN only, and not every machine in your network.

Regarding addressing, yes you will need to divide up your address space. Each VLAN will need to be on a different subnet.

Hope this helps

Kevin Dorrell

Luxembourg

[Syed Aman Hussain]

Thanks for your seggestions

It is really helpfull for me

Thanks Kevin

Regards

Aman

[Jan Hrnko · Accepted solution]

Hi Aman,

as Kevin said, that's a huge ammount of users on a single VLAN. You want to increase the network performance by using VLANs. That can be achieved, but in a slightly different way. You won't increase the performance itself but rather just drop the load on the whole network. That is because you will reduce the number of hosts per vlan and increase number of broadcast domains - that means that broadcast won't be sent throughout the whole network but just inside that current VLAN. When you implement VLANs you will need to route somehow between them (Router-on-a-stick or use a SVI on multilayer switch), because VLANs need to be in different subnets.

The use of SVI (switch virtual interfaces) on a multilayer switch is a better choice because everything is hardware switched and routed as an opposite to Router-on-a-stick solution where router needs to perform routing decisions by software.

Best regards,

Jan

[Jason Dance · Accepted solution]

I agree with the two postings above, you have a large flat network that would benefit by reducing the broadcast domains by using vlans.

Another suggestion I have: once you have finished your network division, you might want to consider provisioning each floor stack of 3750 switches with multiple fiber connections and bundle them into an etherchannel back to your core.  This will increase redundancy, and also give you additional bandwidth on your uplinks to the core.  If you are not worried about redundancy, then I would monitor those fiber links to see if you are saturating the fiber first before going down this path.

HTH

Jason

[Syed Aman Hussain]

Thanks for reply me

its very help full for me

Thanks again

[Jan Hrnko]

Hi Aman,

I am happy to hear that. Take care.

Best regards,

Jan