6500 in HA

Answered Question
Mar 25th, 2009

Hi Everybody,

I am running a campus network with 1 6500 Switch as Core switch and 3560 Switch as distribution switches.

I have purchased another 6500 Switch for redundancy. I am confused how to integrate the new 6500 switch to the existing network. I wondering whether to configure HSRP or not. I am aware of HSRP configuration in routers with one interface. But here i have multiple VLANs are configured.

Kindly look at the diagram attached, and help me how to go with. Whether a dedicated cable is required between the switches and whether HSRP has to be configured or not?

Thanks in advance

R.B.Kumar

I have this problem too.
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Correct Answer by Jon Marshall about 7 years 10 months ago

RB

Then you need to connect your 2 6500 switches together. This is usally done using an etherchannel link. The link can be either L3 or a L2 trunk. The ideal campus design is a L3 link but that requires that each access-layer switch and in your case distro switch has only one vlan on it or to put it another way you have not spanned vlans across access-layer/distro switches.

If you have spanned vlans then use a L2 etherchannel trunk between your 2 6500 switches and use HSRP.

Jon

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Jon Marshall Wed, 03/25/2009 - 04:55

RB

Generally speaking HSRP is not needed in the core of the network. With your existing 6500 what are the links from the 3560 switches ie. are they L2 trunk links or are they L3 routed links.

Ideally you have the distribution switches handling the inter-vlan routing for the access-layer vlans and then the 3560 switches would be connected to the 6500s with L3 routed links. That way you have redundancy from the distro to the core with 2 equal cost L3 paths.

Jon

hclisschennai Wed, 03/25/2009 - 11:29

Hi Jon,

Thanks for your comments.

I absolutely agree with your point.

But in my setup, even though Distribution switches are 3560(L3), i am doing all VLAN routing in the core only.

Thus the link between Distribution and core is trunk and not L3.

In this case, whether HSRP is required in core?

Thanks in advance & regards

R.B.Kumar

Jon Marshall Wed, 03/25/2009 - 12:20

RB

If your 6500 is doing all the inter-vlan routing and the 3560 switches even though they are capable of L3 are only acting as L2 then yes you should look to use HSRP or GLBP between your existing 6500 switch and the new one.

Jon

lamav Wed, 03/25/2009 - 12:30

Jon is absolutely right.

But my question is: Why in Sam's Hill would you have a routed distribution layer only to relegate inter-vlan routing to your core?? Would you be offended if I said that was insane???

Is there a REALLY good reason for that?

Victor

hclisschennai Wed, 03/25/2009 - 12:31

Hi Jon,

Good. I think i am travelling in right direction. Thanks.

Then, do i need to connect these two 6500 switch using a dedicted cross cable for hello packets.

Why i am raising this question is because, in normal LAN we use a L2 switch in between the Routers/Switches running HSRP and this same L2 switch will be used for connecting users.

How to do this in campus infrastructure as Optical Fiber cables are directly terminating in the 6500 switch where it is not possible to put a L2 switch inbetween Distribution and Core switch as mentioned in the diagram i attached earlier

R.B.Kumar

Jon Marshall Wed, 03/25/2009 - 12:35

RB

Perhaps a bit of clarification would help.

As Victor points out this does seem a bit odd.

Your 3560 switches. Are they doing any inter-vlan routing are they purely acting as L2 devices ?

Jon

hclisschennai Wed, 03/25/2009 - 12:52

Hi Jon,

I too agree Victor's point. It will be a good design if 3560 does intervlan routing and 6500 is connected thru L3 backbone.

But the current setup is like what i described. Here now all 3560 distribution switches are working a pure L2 switch. InterVlan is happening in core only.

R.B.Kumar

Correct Answer
Jon Marshall Wed, 03/25/2009 - 12:58

RB

Then you need to connect your 2 6500 switches together. This is usally done using an etherchannel link. The link can be either L3 or a L2 trunk. The ideal campus design is a L3 link but that requires that each access-layer switch and in your case distro switch has only one vlan on it or to put it another way you have not spanned vlans across access-layer/distro switches.

If you have spanned vlans then use a L2 etherchannel trunk between your 2 6500 switches and use HSRP.

Jon

hclisschennai Wed, 03/25/2009 - 13:04

Hi Jon,

Thanks for your valuable comments and input. I will implement as you suggested

I appreciate your guidance in this case.

R.B.Kumar

apdatasoft Thu, 03/26/2009 - 00:56

Hi RB,

What Jon said was right.

But what model is the supervisors of your 6500 switches...? Does it Support the VS..

If it is supports VS, rather you can do VS in between the 6500 switches instead of traditional Ether-channels.

But think about the routed model on your Dist switches itself. That would make a sensible design in this kind of network, and i have been doing the same.

Thanks

AP

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