From: operator sid (ccie1@live.co.uk)
Date: Fri Feb 06 2009 - 12:37:20 ARST
I have read it,and unfortunately its not a good document, i was hoping someone could explain better...
________________________________
> Date: Fri, 6 Feb 2009 14:09:48 +0000
> Subject: Re: Understanding RSTP - Please can someone explain this?
> From: way2ccie@googlemail.com
> To: ccie1@live.co.uk
> CC: ccielab@groupstudy.com
>
> This might help if you have not read it before
>
>
>
> http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml
>
>
>
> Ravi
>
>
> On Fri, Feb 6, 2009 at 12:25 PM, operator sid> wrote:
>
> Hi Group
>
>
>
> I am still confused about how RSTP is implemented. From what i understand the major difference is that STP
>
>
> used Timers for Loop prevention whereas RSTP coordinates between neighbors via messages (proposal/aggreement) to turn on links
>
> more quickly after topology changes and is "timer free".
>
>
>
>
> However, I have not noticed any difference in the configuration from the legacy STP
>
> configurations and the RSTP configuration on cisco devices. Or are there any differences??
>
>
>
> I have read in documentation that RSTP natively includes features
>
> like UplinkFast, BackboneFast and PortFast. So are these features now
> obsolete
> and not needed to be configured if you are running RSTP.
> (Although i have seen Portfast still configured along with RSTP on many
> switches)
>
>
>
>
> Also can someone explain the below Points from Cisco Documentation
>
>
>
> 1) should STP be disabled on edge ports all together as suggested below?
>
>
>
> "STP edge ports are bridge ports that do not need STP enabled, where loop protection is not needed out
>
>
> of that port or an STP neighbor does not exist out of that port. For RSTP, it is important to disable STP
>
> on edge ports, which are typically front-side Ethernet ports, using the command bridge
>
> bridge-group-number spanning-disabled on the appropriate interface. If RSTP is not disabled on edge
>
>
> ports, convergence times will be excessive for packets traversing those ports."
>
>
>
> 2) It seems RSTP relies on duplex setting to determine inter-switch links. What is the configuration to explicitly
>
>
> configure RSTP link types? (I couldnt find this in the documentation)
>
>
>
> "RSTP can only achieve rapid transition to the forwarding state on edge ports and on point-to-point links.
>
> The link type is automatically derived from the duplex mode of a port. A port that operates in fullduplex
>
>
> is assumed to be point-to-point, while a half-duplex port is considered as a shared port by
>
> default. This automatic link type setting can be overridden by explicit configuration. In switched
>
> networks today, most links operate in full-duplex mode and are treated as point-to-point links by RSTP.
>
>
> This makes them candidates for rapid transition to the forwarding state."
>
>
>
> Also i am a bit rough on my RSTP knowledge even after skimming a
> few Cisco documents. Can someone please explain this in simple way.
>
>
>
> Thanks in advance
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