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New Member

question about spanning tree

I see a lot of paper talking about using layer3 switching + routing instead of spanning tree.

I would like to know in cisco enviroment, (cisco catalyst switchs/router) is there any benefit to stop using spanning tree?

Does anyone do using layer3 switching only in large network?

Any comments will be appreciated

Thanks in advance

4 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Bronze

Re: question about spanning tree

Either design has its pros and cons and you must understand the implications when choosing one over the other.

On a routed inter-switch design - you lose the ability to dual home servers so this design may not work in a server farm. If you routed to the access switch, workstations may get a different subnet depending on the switch they are connecting. Take into account larger DHCP scope and more subnets.

On a routed inter-switch design - you limit your L2 domain to a single switch. You have a faster convergence and L2 loops are non-existence.

I know many large companies using both designs and both work quite well depending upon the requirements.

Regards,

Edison.

Hall of Fame Super Silver

Re: question about spanning tree

Hello Julie,

sorry for misunderstanding I should have thought it coould be just a typing error!

Cisco devices default to PVST+ that is proprietary and can interact with legacy 802.1D on a per port basis.

In a multi-vendor environment if all devices support it 802.1s MST can be used.

It requires more management efforts because configuration of

MST region name

MST revision number

mapping of Vlans to MST instances

need to match and need to be configured manually.

MST requires a change of mind that is you are encouraged to plan : that is you can divide the 4094 possible vlans in 64 subsets and you can associate them each subset to a different MST instance.

in this way you just need to choice a vlan from a subset and to create it on devices and you get a zero touch MST campus (that is you don't need to modify all those parameters that cause temporary problems as reported by other users).

the advantage is that the vlans don't need to already exist they can mapped before.

For a multivendor environment MST should be the best choice because it allows to build multiple topologies (one for each MST instance) and it is more scalable then Cisco PVST+ or Rapid PVST (it uses an instance for each vlan to be considered low end cisco switches have limits that can be reached in a campus)

Hope to help

Giuseppe

Hall of Fame Super Bronze

Re: question about spanning tree

if I want implement VoIP and multi-media sulotion, on basic routing/switching site, what improvement I need consider?

QoS

You want to make sure you prioritize VoIP traffic and guarantee bandwidth for mission-critical applications such as Video.

Regards

Edison.

Hall of Fame Super Silver

Re: question about spanning tree

Hello Julie,

Rapid STP is recommended for VoIP applications

and QoS is very important as Edison has noted.

Hope to help

Giuseppe

8 REPLIES
Hall of Fame Super Bronze

Re: question about spanning tree

Either design has its pros and cons and you must understand the implications when choosing one over the other.

On a routed inter-switch design - you lose the ability to dual home servers so this design may not work in a server farm. If you routed to the access switch, workstations may get a different subnet depending on the switch they are connecting. Take into account larger DHCP scope and more subnets.

On a routed inter-switch design - you limit your L2 domain to a single switch. You have a faster convergence and L2 loops are non-existence.

I know many large companies using both designs and both work quite well depending upon the requirements.

Regards,

Edison.

New Member

Re: question about spanning tree

Edison

great thanks for the clarify, one more question, I hear someone said the spanning tree require all the equipment in the domain are unix product, is it true?

Please advice

Hall of Fame Super Silver

Re: question about spanning tree

Hello Julie,

>> I hear someone said the spanning tree require all the equipment in the domain are unix product, is it true?

I've never heard of this.

it is not true.

STP manages OSI Layer2 redundancy, unix is a flavor of operating system on workstations.

no direct relation between the two.

old unix workstations may have specific requirements for OSI L3:

use of RIP

or need of proxy-ARP enabled on routers because they could use the major network mask and not the correct subnet mask.

Hope to help

Giuseppe

New Member

Re: question about spanning tree

sorry, Giuseppe

I wrote by mistake, can I repeat question again.

I heard spanning-tree require all the equipment in the domain with same product, for example, if I use cisco switches, I have to use cisco switches all the time, if I want mix with to other switchs, I will have protential problem.

Is it a right statement? Please advice.

Thanks in advance

Julie

Hall of Fame Super Silver

Re: question about spanning tree

Hello Julie,

sorry for misunderstanding I should have thought it coould be just a typing error!

Cisco devices default to PVST+ that is proprietary and can interact with legacy 802.1D on a per port basis.

In a multi-vendor environment if all devices support it 802.1s MST can be used.

It requires more management efforts because configuration of

MST region name

MST revision number

mapping of Vlans to MST instances

need to match and need to be configured manually.

MST requires a change of mind that is you are encouraged to plan : that is you can divide the 4094 possible vlans in 64 subsets and you can associate them each subset to a different MST instance.

in this way you just need to choice a vlan from a subset and to create it on devices and you get a zero touch MST campus (that is you don't need to modify all those parameters that cause temporary problems as reported by other users).

the advantage is that the vlans don't need to already exist they can mapped before.

For a multivendor environment MST should be the best choice because it allows to build multiple topologies (one for each MST instance) and it is more scalable then Cisco PVST+ or Rapid PVST (it uses an instance for each vlan to be considered low end cisco switches have limits that can be reached in a campus)

Hope to help

Giuseppe

New Member

Re: question about spanning tree

hi Giuseppe

thanks for you great help.

one more question, for cisco equipment enviroment, if I want implement VoIP and multi-media sulotion, on basic routing/switching site, what improvement I need consider? for example, I should use Rapid PVST or PVST+?

Many Regards

Julie

Hall of Fame Super Bronze

Re: question about spanning tree

if I want implement VoIP and multi-media sulotion, on basic routing/switching site, what improvement I need consider?

QoS

You want to make sure you prioritize VoIP traffic and guarantee bandwidth for mission-critical applications such as Video.

Regards

Edison.

Hall of Fame Super Silver

Re: question about spanning tree

Hello Julie,

Rapid STP is recommended for VoIP applications

and QoS is very important as Edison has noted.

Hope to help

Giuseppe

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