LAN setup

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Mar 7th, 2008
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Hi,


I have two idea to design the LAN. attched two design diagrams.


for the LAN design 1,


- the distributed layer switch is two 37xx. the core may be two Cat 46xx.


- the access layer switch is 12 port unmanage switch.


- total 500 per floor


- 10 Vlan for each floor, 5 for data, 5 for ip phone


- around 100 node per one Vlan




the LAN design 2,


- the distributed layer switch is five 2924. the core may be one Cat 37xx.


- the access layer switch is 12 port unmanage switch.


- total 500 per floor


- 10 Vlan for each floor, 5 for data, 5 for ip phone


- around 100 node per one Vlan



I don't think it will have performance issue if we choose "design 2". Cat 2924 can handle 100 nodes or more.


any reason / advantage in "design 1", not in "design 2" ?


rdgs








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Edison Ortiz Sat, 03/08/2008 - 11:57
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Hi Anita,


How you plan on configuring the access-port for voice and data with an unmanaged switch?


Out of the 2 designs, I prefer the first one by using a 3750 in the distribution layer. The distribution layer should be a device that performs some kind of routing and the 2924 does not.


Of course, the main concern is the access-port device selection and it must not be a unmanaged switch.


HTH,


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Edison.

lamav Sat, 03/08/2008 - 12:09
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edison:


I share the same concern regarding unmanaged swithces.


Do you think a 3750 is robust enough to handle inter-vlan routing for the number of users she mentions? It seems a bit weak for a distribution layer switch...no?



Thanks


Victor

Edison Ortiz Sat, 03/08/2008 - 14:14
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It should do an adequate job for inter-vlan routing. Based on the OP's device list, it seems they are running on a tigh budget.


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Edison.

lamav Sat, 03/08/2008 - 14:20
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gotcha

anitachoi3 Sat, 03/08/2008 - 20:09
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Hi Edison,


yes, there is no L3 routing on 2924.


the distributed layer should be 37xx.


If I implement the backup solution

- 3750 x 1 for each floor (total 3750 x 4)

- 3750 x 1 for cold standby (backup all floors)


Any suggestion?


regarding the Access switch, I use 3COM (24 ports). the design is:


- 5 VLAN (data) per floor

- 5 VLAN (voice) per floor

total 10 VLAN


- 100 nodes per VLAN, so

- 3COM x 6 for one VLAN (data)

- 3COM x 6 for one VLAN (voice)

(I will not fully use all 24 ports, I will use 18 ports only)


total 3COM per floor:

5 vlan x 12 3com = 60 3com switch


total 3COM:

60 x 4 = 240 3com (24 port), support 2000 users and 2000 ip phones


the port utilization is around 70% of access layer switch. is it reasonable calculation?


rdgs




Edison Ortiz Sat, 03/08/2008 - 20:18
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3750 is a stackable switch so you don't need to run it on a 'cold standby' mode. When stacked, they are both active unlike the Dual Supervisor design on 4500 and 6500.


What are your plans for the access-layer? You can't implement VoIP with unmanaged switches at that layer.


__


Edison.

anitachoi3 Sat, 03/08/2008 - 20:26
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Hi Edison,


three 3750 are in different floors, does it has a very very long stack cable to link up all of them? (from 11/F - 14/F)


Moreover, if the 3750 is down on 11/F, all voice /data are down on 11/F. the cold standby is the only one solution, isn't it?


rdgs



Edison Ortiz Sun, 03/09/2008 - 08:51
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If you connect a VoIP phone to those 3COM unmanaged switches, does it know to tag Voice traffic with the appropiate DSCP/COS tags?


Most likely, the answer is no.


Do you know that in order to have a VoIP Phone and a PC sitting behind the VoIP, you need to configure the switchport for trunk or auxiliary Vlan?


You can't do that with an unmanaged switch.


Again, before we go crazy with the distribution device, let's nail down the access-layer which is the main problem in your design.


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Edison.

anitachoi3 Mon, 03/10/2008 - 10:03
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Hi Edison,


you are right, I will implement the 10 VLAN for each floor. 5 for data and 5 for voice. I am not expert on LAN design and some cisco product, that's why I ask for expert to comment on it.


regarding the trunk, I need to implement it. any idea for the trunk design?


regarding the access switches, I base on the users/floors to calculate it. The figure should be close to "future live".


Could you give me some idea if

"there are 500 users for each floors and it has 4 floors. how to design the access layer switch?"


rdgs



Edison Ortiz Mon, 03/10/2008 - 17:27
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regarding the trunk, I need to implement it. any idea for the trunk design?



To trunk or not to trunk depends on the VoIP Phones you are planning to use. Cisco VoIP supports the auxiliary Vlan and I'm sure others too but you must contact the VoIP manufacturer for assurance.


Example,


interface fx/x

switchport mode access

switchport access vlan 10

switchport voice vlan 20


If you need to trunk, the native Vlan on this trunk will be the data Vlan and you would have the Voice Vlan allowed on the trunk as well.


Example,


interface fx/x

switchport encapsulation dot1q

switchport mode trunk

switchport trunk native vlan 10

switchport trunk allowed vlan 10,20



how to design the access layer switch?"


I believe you are asking how many switches do you need.


One thing I must recommend is to perform a site survey and understand the customer's needs.


You can't count switchports or switches based on the number of users.


An user may need 2 or more connections for whatever reason. You need to account for network printers or other network related devices. You need to account for conference rooms, etc.


A network design can't be performed on a post to a forum. You must contact a qualified person that could work with you one on one onsite.


HTH,


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Edison.


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