08-28-2008 03:12 AM - edited 03-06-2019 01:02 AM
Hi,
We've bought 9x 3750s to setup for a new office. We will be stacking them but I've also been asked to setup VLANs (see attachment). So I wanted to know:-
a) Is this a good idea on a stacked system and,
b) will it be difficult to implement.
I'd be grateful for any comments - I am new to this! Am more than happy to provide more info if needed.
-H
08-28-2008 03:19 AM
a) Althought they are 9 physical switches, they are 1 logical switch from a config point of view.
b) No
The VLAN setup you have - indicates that each switch is a single point of failure for a specific vlan number/ip subnet. Perhaps not the best way to go about it in my opinion.
Perhaps you might consider 3 switches in a stack group, that are connected via redundant fibre trunk links.
Then assign specific ports into the relevant VLAN's.
HTH>
08-28-2008 03:30 AM
Thanks for coming back. I wanted to clairfy a couple of things.
Given that the 9 switches are 1 logical switch from a config point of view is it possible to set each one up with VLANs as described?
Do you think there will be a performance benefit of having mulitple VLANs - or do you think just 1 voice and 1 data VLAN will suffice?
Is the benefit of the "3 switches in a stack group" configuration you propose to tolerate a switch failure?
Appreciate you help with this.
-H
08-28-2008 03:36 AM
Given that the 9 switches are 1 logical switch from a config point of view is it possible to set each one up with VLANs as described? Yes - you would create the vlans on the master switch. The assign the relevant interfaces into the speicifc VLAN you want.
Do you think there will be a performance benefit of having mulitple VLANs - or do you think just 1 voice and 1 data VLAN will suffice? - for eas of troubleshooting - data vlan and voice vlan. If that is all you have keep it simple. if you have to segregate inter-vlan traffic, then do so.
Is the benefit of the "3 switches in a stack group" configuration you propose to tolerate a switch failure? Yes - only if you want a vlan/ip subnet per switch. If you decide with only 2 vlans, stack all 9.
However if you want to add a 10th switch, you cannot - 9 is the max limit in a stack group.
Another option could be 1 stack of 5 switches, and the other stack of 4 switches. So you could add 4 switches to stack 1 and 5 switches to stack 2.
I always try to plan for the future.....people allways need more ports!!!!
HTH>
08-29-2008 06:46 AM
I've just found out the will be using phones and PCs on the port. Hence I will need 2 VLANs on each port and the 2 stack option is not viable.
We've also just found out that the switches supplied are not PoE - again needed for the phones. Nice!
Anyway thanks for your help - much appreciated!
-H
08-29-2008 06:53 AM
Why is the 2 stack option not viable?
In one of my offices, I have 22 switches, in various stack configurations - mainly 3 switch stacks. All switches have VoIP phones connected, with a PC connected to the phones?
All stacks are in seperate racks, with seperate power and UPS.
If you bundle all switches into 1 stack and all in 1 rack, all connected to the same power - where is your resiliance? Your stack is a single point of failure?
What are you using for Layer 3 routing? A seperate router or the 3750 MLS? Are you connecting the layer 3 into the stack? Is your stack going to provide Core<>Dsitribution<>Access layers all in one go?
Think failover, think redundancy.
08-29-2008 06:57 AM
I've obviously misunderstood! I thought you were suggesting 1 VLAN per stack - my apologies.
I will be using the MLS and will be providing all three layers - do you see a problem with this?
08-29-2008 07:42 AM
OK here's the thing with 1 stack.
You have layer 2/3 functions all in one stack - nice for standardisation, one stop shop for troubleshooting. If the master fails, then the next in-line will take over - lovely.
If the whole stack fails - you have lost everything no connectivity to anything - bad idea.
If you are going to core-dis-access all in the stack - you need to split it (in my opinion) you don't want all your eggs in one basket - you need to plan for the worst and hope for the best.
If you have critical servers etc - they need a redundant topology. I would:-
1) Have 2 stacks
2) Configure Trunking between the stacks.
3) Configure VTP - easy for vlan creation blah blah
4) Configure layer 3 interfaces in both stacks for management and inter-vlan routing if needed
5) Either configure HSRP or VRRP between the 2 stacks, if the primary layer 3 interface fails, the secondary takes over.
6) With the above - with any mission critical servers, they should have dual NIC's - then cable 1 into each stack.
7) Distribute the VoIP phones and PC's between the stacks - say a 50/50 if possible
For a belts a braces thinking if the site is really important - you would have two internet links and two firewalls, each on their
own stack.
So if 1 stack complety fails (un-likely) at least 50% of the site can still carry on working!
Like I said - plan for the worst and hope for the best! just my opinion
HTH>
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