Two redundant Switches

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Nov 7th, 2007
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Hello there,

we want to build a network with two switches that are interconnected. The goal is to be able to enable "teaming" on servers with two NICs, so that if one Switch fails, network connection is still available. We now dont now, whether we need "ENHANCED MULTILAYER IMAGE" when using Catalyst 3750 switches. Can anyone help? (we're are quiet new to the Cisco world). Thanks, Uli

Correct Answer by Jon Marshall about 9 years 6 months ago

Hsrp will be used to ensure that if one of your switches dies then the server can communicate via the other switch.


If the NIC on a server dies it will just use it's other NIC, but the active HSRP gateway will not change eg.


active HSRP gateway on SW1.

active NIC on SW1.


NIC fails, now active NIC is connected to SW2. Traffic goes from NIC to SW2 and if it is to be routed to a different vlan it is switched across your layer 2 trunk to active HSRP gateway on SW1.


As i say HSRP is for a switch dying rather than an server NIC.


HTH


Jon

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Jon Marshall Wed, 11/07/2007 - 13:26
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Hi


For what you describe you do not need the Enhanced image. What you need to do is connect your 2 switches together via a layer 2 trunk and then run HSRP between your 2 switches for the L3 vlan interfaces.


All of this can be done with the Base image however if you want to run a full routing protocol such as EIGRP/OSFP etc. on the 3750's to peer with other L3 devices in your network you will need the Enhanced image.


HTH


Jon

VCUGmbH66693 Wed, 11/07/2007 - 13:30
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Dear Jon,

thx for that answer.

I am still reading through all the documents on this site.


So it should work using two WS-C3750-24TS-S (IP Base Image). Could the trunk then be build using one of the two SFP uplinks each of these routers have?


Thanks again for your help.

Uli


Jon Marshall Wed, 11/07/2007 - 13:32
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Yes absolutely you can do this with the SFP's.


I would recommend you have a look at the extra features you get with the Enhanced Image just in case you think you might need them in future.


Jon

VCUGmbH66693 Wed, 11/07/2007 - 13:36
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Sorry, and one more: what happens when the NIC of the server fails that is connected to the active switch? Is HSRP really the best solution for our case?

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Jon Marshall Wed, 11/07/2007 - 13:41
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Hsrp will be used to ensure that if one of your switches dies then the server can communicate via the other switch.


If the NIC on a server dies it will just use it's other NIC, but the active HSRP gateway will not change eg.


active HSRP gateway on SW1.

active NIC on SW1.


NIC fails, now active NIC is connected to SW2. Traffic goes from NIC to SW2 and if it is to be routed to a different vlan it is switched across your layer 2 trunk to active HSRP gateway on SW1.


As i say HSRP is for a switch dying rather than an server NIC.


HTH


Jon

VCUGmbH66693 Wed, 11/07/2007 - 13:47
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Thx, Jon. So we are on the safe side with your solution. And both can happen, One NIC may fail and one SW mail fail. Thx, Uli

Jon Marshall Wed, 11/07/2007 - 13:48
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Uli


Yes, you will have server resiliency and switch resiliency with this setup.


Appreciate the ratings.


Jon

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