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New Member

Uplinkfast in 'non-delta' switch configuration

Does anyone know if it is possible to use uplinkfast in a switch configuration other than the 'delta' type always shown in the Cisco documentation?

I have 4 switches, 2 core (6506+msfc2 running hybrid) and 2 server access (5500 w/Sup3). They are connected in a U configuration - 1 link from 1st core to 1st access, 2 links between 1st and 2nd access switches and another 1 to second core switch. One of the links between the access switches blocks because the links are on different modules and Cat55XX can't port channel.

I'd like to use uplinkfast on the access switches to allow the blocking link to forward soon after the forwarding link fails (to avoid HSRP problems) but have been told this may result in network unstability. Any thoughts?

5 REPLIES
New Member

Re: Uplinkfast in 'non-delta' switch configuration

Where is your root bridge and secondary root bridge? Are the core switches the roots (primary and secondary)?

Rgds,

NM

New Member

Re: Uplinkfast in 'non-delta' switch configuration

yes, should have mentioned: 1st core switch is root and second core switch is secondary root. Access switches both have the high uplinkfast assigned priority 49152.

regards,

SB

New Member

Re: Uplinkfast in 'non-delta' switch configuration

Hi.

Uplink fast allows a switch to have a "backup" link to the root bridge that starts forwarding as soon as the main link goes down. Before going further, are your core switches connected directly?...

Rgds,

NM

Re: Uplinkfast in 'non-delta' switch configuration

What is your exact topology?

Is it like following?

A1 ==== A2

|*********|

|*********|

C1-------C2

(where * means "nothing", this "editor" is removing spaces from the output)

Regards,

Milan

New Member

Re: Uplinkfast in 'non-delta' switch configuration

The topology looks like this:

A1====A2

|*********|

|*********|

C1*****C2

(where *** means nothing)

there is no layer 2 connection between the core switches (only a layer 3 connection - the core 'switches' are primarily routers)

The reason citied for uplinkfast possibly causing network unstability was that in this configuration, when the blocking link goes forwarding the switch has to flood it's CAM table over the newly forwarding link to the neighbouring switch e.g. A2 sends all it's mac addresses to A1. I have been told that the access switch A1 could meltdown by having to accept all these mac addresses it already knows on the 'old' port on the newly forwarding port.

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