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Networking & Switches: L2 vs L3

Posted on 2013-10-22
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Last Modified: 2013-10-29
We have a Cisco Small Business SG300 28 port switch (layer 3).
http://www.cdw.com/shop/products/Cisco-Small-Business-SG300-28P-switch-28-ports-managed-desktop-rac/2198241.aspx

We're adding several servers (VMware ESXi) to this environment, and this switch does not have enough ports to support both servers, so we are looking to buy an additional switch.

My questions:
1. What kind of switch should we buy: Layer 2 vs Layer 3?
2. If we went with a layer 3 switch, would the physical switch connectivity to one another be the same as if we bought a layer 2, switch -- Cisco EtherChannel?
3. In terms of the switch config, what major config differences would there be if we went with a layer 3 switch?

My thoughts:
1. Since we already have a layer 3 switch, we don't need to buy another because a layer 2 switch would forward all traffic that needs to be "routed" to the existing layer 3 switch -- using "CiscoEtherchannel" -- I believe. I primarily work with ProCurve switches, so in HP terms I would use a Trunk.
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Question by:pzozulka
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by:Soulja
Soulja earned 1600 total points
ID: 39591730
1. What kind of switch should we buy: Layer 2 vs Layer 3?

If you are not going to use the Layer 3 functionality than Layer 2 is fine.


2. If we went with a layer 3 switch, would the physical switch connectivity to one another be the same as if we bought a layer 2, switch -- Cisco EtherChannel?

The physical connectivity would be the same

3. In terms of the switch config, what major config differences would there be if we went with a layer 3 switch?

No difference, unless you wanted to use the layer 3 function of the switch.
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by:pzozulka
ID: 39591751
We will definitely be using layer 3 functionality.

But, since we already have a layer 3 switch, do we really need another L3 switch since a L2 switch can use the existing L3 switch's L3 abilities.
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by:Soulja
ID: 39591772
Yeah, that's what I meant. If you won't be using the layer 3 functions on the new switches than you are fine getting layer 2 only switches.
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by:Soulja
Soulja earned 1600 total points
ID: 39591775
On another note it would be good to have another layer 3 switch for redundancy. You could use HSRP for the exisiting layer 3  vlan interfaces you have for the current layer 3 switch.
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by:giltjr
giltjr earned 400 total points
ID: 39592256
I agree with Soulja last comment.

How many new ports do you need?

If possible I would suggest you get another SG300 28.

Each ESXi Server should have at least one connection to each switch.  Have the switches setup to use HSRP and connect them to each other.

This way if one switch goes down you still have access to all your VM's.
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by:pzozulka
ID: 39592297
giltjr: We need about 24 new ports.
ESXi Server should have at least one connection to each switch
ESXi host only supports NIC teaming on a single physical switch or stacked switches.

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=1001938&sliceId=1&docTypeID=DT_KB_1_1&dialogID=69836556&stateId=1 0 69844573
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by:Soulja
Soulja earned 1600 total points
ID: 39592781
Sorry, I neglected the fact that you will be only using two switches, so hsrp would be pointless since your servers are directly connected. Thus if one switch fails you lose half your devices anyway.
That being said, if the prices are close I would still pick a layer 3 just to have that option in case the existing layer 3 fails and then you would have absolutely no routing.
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by:pzozulka
ID: 39592839
Thanks. Do you know if there is a major difference between the Small Business SG300 switches and the catalyst switches?

The SG300 is a layer 3 switch, yet a catalyst layer 2 switch (2900 series) costs like 3 - 5 times more. Why?

Sorry, I don't work with Cisco much.
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by:giltjr
ID: 39593028
I'll have to check how we do it, but we do NIC teaming to different switches.

Are you getting the new Cisco 2900 ISR's confused with the old Catalyst 2900 switches?

The Catalyst 2900 switches are out of support and you can pick them up for under $100.

The 2900 ISR's are L3 routers and they are like $2,000.
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by:pzozulka
ID: 39593998
Yea it would be great to find out if you're doing link aggregation to different switches. I know you can connect a NIC team to different switches to get redundancy, but then you're not getting link aggregation.

Here are the switches I was referring to: http://www.cisco.com/cisco/web/solutions/small_business/products/routers_switches/catalyst_2960_series_switches/index.html

I looked up a few and 2960-24TC-L is right under $1000 fro 24 port and even more expensive for 48 port.

Do you have any model numbers or links you can suggest for a relatively new Cisco L2 Catalyst switch for under $100?
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Soulja earned 1600 total points
ID: 39594050
Nah, you won't find any newer L2 Catalysts for under $100. If you can get nic teaming to two different switches, while you won't have load sharing, you would have redundancy since I assume you would be in a active/standy mode. If that be the case, HSRP is back in play.
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by:giltjr
ID: 39594337
Although they both start with "29" a 2900 series (Catalyst 2900) is different from a 2960.  The 2960's are still supported and are in the $1,000 plus range.  The 2900's I was referring to were used.

I would have to look at the details, but my initial guess is the 2960's are geared towards larger networks and can support more VLAN's that the SG300's.  

We are not doing link aggregation, we want redundancy and availability.  

Do you really have enough traffic to/from your servers that you need link aggregation?
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