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3750 redundancy help needed

hi all

i'm attaching my network diagram.

pleas eguide me how to configure redundancy in this.i'm comparitively new to switching.

Thanks in advance.

Regds

Joseph

7 REPLIES
VIP Purple

Re: 3750 redundancy help needed

Hello Joseph,

if this is your physical setup, you already have (the potential for) redundancy. From what I can tell from your drawing, all switches have redundant connections, if you have Spanning Tree enabled, that alone would take care of redundancy. You might want to configure the core switches as the primary and secondary root for your VLAN's (with the command 'spanning-tree vlan x root primary/secondary').

You could also use Spanning Tree load balancing, in order to make use of the redundant trunks, check this document:

VLAN Load Balancing Between Trunks Using the Spanning-Tree Protocol Port Priority

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800ae96a.shtml

If you start from scratch and do not have a lot of experience with switch configurations, this might be hard to accomplish, and requires some planning regarding which VLAN's are sent over which trunk.

I guess you could check if you already have redundancy, by making sure that all VLAN's have forwarding and blocking ports on each switch, which they should, judging from your drawing. Use the command:

show spanning-tree vlan X

that will show you the forwarding and blocking ports.

Hope that makes sense, let me know if you need more specific help...

Regards,

GP

New Member

Re: 3750 redundancy help needed

Hi Gp thanks for your support.

actually i'm planning to implement switches like this.

so if the active link fails redundant should take over rt?. so for this is it necessary to configure any hot standby protocols.i should give some weightage active & redundant links rt.

kindly reply with your valuable suggestions.

Regds

VIP Purple

Re: 3750 redundancy help needed

Hello Joseph,

indeed, just start out with letting spanning tree choose the active and redundant (blocked) ports. Just make sure that your core switches are the root for your VLAN's, as described in my previous post. As for HSRP, if you implement inter-VLAN routing (on your core switches), that would indeed be an option, to introduce further redundancy into your network...

Regards,

GP

New Member

Re: 3750 redundancy help needed

hi GP

i'm not planning for any VLAN.It will be a /24 network.

there wont be any VLAN.so in this case how you want me to proceed.Please suggest

VIP Purple

Re: 3750 redundancy help needed

Hello Joseph,

a flat network makes implementation rather easy: just connect the switches, everything will be in the default VLAN (1), and spanning tree, as said before, will take care of the redundancy. Make sure you configure the core switches as primary and secondary root for VLAN 1.

Be aware though not to put too many hosts into that VLAN, the general rule of thumb is to limit a VLAN to roughly the size of a class C subnet (254 hosts). If you have more than that number of hosts, your network might slow down, and you will eventually have to introduce additional VLAN's (and everything else involved, such as trunks, inter-VLAN routing, VTP)...

Regards,

GP

New Member

Re: 3750 redundancy help needed

ok so there is no need of HSRP or any other hot standby protocol.GP can you please explain the below statement.

"Make sure you configure the core switches as primary and secondary root for VLAN 1."

Regds

Joseph.

VIP Purple

Re: 3750 redundancy help needed

Hello Joseph,

in spanning tree, one switch is always selected as the root switch for the tree, all data flows through that switch, that is why it is important to select the most powerful and most central switch as the root. In your case, these are most likely the core switches. By configuring the core switches with those commands, you influence the root selection process, and you make sure that the core switch actually does become the root...

Does that make sense ?

Regards,

GP

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