[j-nsp] Network design problem in a bridged setup with 2x Juniper MX and some Brocade SuperX

[Huan Pham]

Hi Tobias,

Upstream or Downstream is from your perspective. RTG does not run between devices, so it does not care if the redundant paths are connected to upstream or downstream!! All it cares is that if the primary link is up, the the SW blocks all traffic comming and it does not send any traffic via those redundant paths, basically breaks any potential loop. If the primary link is down then the switch starts forwarding traffic via the next preferred link.

If you have a diagram and you turn it upside down, then your upstream switches now become downstream! Let's think it that way.

You are right that in the Juniper config example it is configured on an access switch, and it may be the best practice if you have the control of both core and access switches, e.g in your Data Centre.

But in case you want to control the loop when you connect with customer, you want to run RTG on your device! If you trust your customer doing the right thing then you can have the customer switch to connect to more than one of your devices, and run RTG on his switch. If he does not configure it properly then you are open to the loop again.

Huan

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Huan Pham

On 31/01/2013, at 8:08 PM, Tobias Heister <lists at tobias-heister.de> wrote:

> Hi,
> 
> Am 31.01.2013 03:06, schrieb Huan Pham:
>> The simplest solution is redundant trunk group (RTG). Pls check if your switches facing customer support it.
>> 
>> On Cisco, i think you can use "interface backup" command to do the same. 
>> 
>> The down side with these solutions is customers have to connect to the same physical switch or virtual chassis.
> 
> Why should they need to connect ot the same upstream switch?
> 
> RTG or flexlink is only run local on the TOR or Access Switch, the upstream switch does not need to know about it. You can connect the access switch running RTG/flexlink to two different
> Core Switches without any problems. We do this in basically all of our datacenters.
> 
> You only need to make sure, that the Core to Core Switch Link does not fail or at least is redundant enough, otherwise you may end up with a split situation as RTG/flexlink does not know
> about link errors upstream.
> 
> regards
> Tobias
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