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Occasional Contributor
Posts: 7
Registered: ‎10-14-2008

ISL Trunking with different distance

Hi everybody

I ask you about the next doubt:

We have a fabric with two switches without redundant path. It means, we only have one ISL that is connecting these two switches.

In order to mantain high availability using a diferent path, we are considering the possibility of to have a trunking with two ISLs

The first ISL is linking 2 switches separated by 7 Km

The second ISL may be link 2 switches separared by 28 Km

Is it possible configure one trunking with those characteristics ? It means, one ISL (7km) and the other ISL (28 Km) ?

Why yes, or why not ?

Thanks in advance

Peternt

External Moderator
Posts: 4,974
Registered: ‎02-23-2004

Re: ISL Trunking with different distance

peternt,

your question is very confused!

Your wrote here:

--->>> We have a fabric with two switches....

--->>> The first ISL is linking 2 switches separated by 7 Km.... ->>> The second ISL may be link 2 switches separared by 28 Km

Do you have One or Two Fabric wich each 2 Switch ?

TechHelp24

TechHelp24
Occasional Contributor
Posts: 7
Registered: ‎10-14-2008

Re: ISL Trunking with different distance

OK

I expect that this graphic explains best the issue

best regards

Peternt

External Moderator
Posts: 4,974
Registered: ‎02-23-2004

Re: ISL Trunking with different distance

Peternt,

the best way for realized this distance ( 27 KM ) , must be used Two 7500E Router - Ex. trough DWDM - , additional you need a Extended Fabric License.

TechHelp24

TechHelp24
Occasional Contributor
Posts: 5
Registered: ‎02-02-2008

Re: ISL Trunking with different distance

Hi Peternt

Brocade ISL trunk is very efficient but, it doesn't stand distance differences in links forming an ISL trunk. The maximum difference is 30 meters or 400 meters. I don't remember exactly, but in your case ISL trunk won't work.

ISL trunk is best, but DPS (dynamic path selection) is next best thing. Would that be enough? To use that you'll have to have DLS (Dynamic load sharing) on and exchange based routing in use. See commands below:

dlsshow (to see if it is already on), dlsset (to enable DLS)

aptpolicy (to see which one is in use), aptpolicy 3

This way you'll have 2 separate ISLs, but they balance traffic evenly. In case one link fails, fabric reconfigures it self and continues working. But remember excange based routing should not be used with HP EVA CA, or at least not yet. I don't know if there is any other disk systems that won't handle it. And yes, you need extended fabric license to configure long distance parameters (buffer-to-buffer credits) to ISL interfaces.

terma

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