OSPF, Etherchannel and 100Gb networks help

Unanswered Question
Oct 3rd, 2005
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Hi All


We have a new design which involves the following.


Background

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Two Core 6509 with sup 720's (Ca +Cb)

Two Serverfarm Switches 6509 with Sup 720's (SFa +SFb)

3 4507 switches with Supervisor V. (Ua - Uc)


The connections are as follows

SFa (2 x 10Gb to Ca, 1 x 10Gb to SFb, 1 x 10Gb to Cb)

SFb (2 x 10Gb to Cb, 1 x 10Gb to SFa, 1 x 10Gb to Ca)

Ua-c ( 1 x 10Gb to Ca, 1 x 10Gb to Cb)


We want to bundle the 2 x 10Gb links into an etherchannel. This will eventualy scale upto 80Gb each. With this in mind we thought about how we would do this with OSPF and this is where my question comes in.


Questions

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1. How do we set OSPF values. Using the auto reference command with 100Gb being a value of 1 means our WAN link at 2mb and its backup link of 128K are swamped and don't register as values (65K being the upper limit). do we statically assign values we work out using a spreadsheet. If we do this fine, its not too much of an issue, but it does lead to question 2

2. If a link drops out of the etherchannel will OSPF recalculate the cost of the link if we have given it a value ourselves rather than let OSPF calculate the cost?

3. Can I use auto cost reference and then set my WAN values statically?


Any advice welcome, any clarifications please post and let me know and I will respond.


My current thinking is to use the auto cost reference for 100Gb = 1 and then work backwards but set the WAN and backup at a static value but I don't know if I can use both at teh same tiem?


Kind regards

Nick


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spremkumar Mon, 10/03/2005 - 03:25
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hi


We did fall into same kinda scenario and we planned to make use of auto-cost reference b/w command under the ospf config but in our case we have all OC-3 and OC-12s connecting out.

so we didnt face or did any tuning on the wan end side similar to what you think out here about ur 2Mb and 128K link which mite appear same in cost if u give the refernence b/w.

i would suggest to work it out as you have mentioned to assign the cost to your primary and the backup link without affecting the interest (cost) of the other active links in your network .


regds


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