Delay on 100Mb Provider links

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Oct 7th, 2008
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For one of our customers we are looking to configure 2*100Mbit connections through a 2 different service providers.

For redundancy the lines should physically follow a different path through the country.

The idea is to bundle both interfaces in a port-channel but we are little bit afraid that packets will come out of sync.

Normally in a port-channel the loadbalancing is done by dest-mac so normally the flow will go over 1 link and there should be no issue.

Does anybody have different experiences ?



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tcordier Tue, 10/07/2008 - 06:20
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I do not think you can create an Etherchannel using two different devices (from different SP's) on the remote end of the link. Etherchannels will only work if the individual links are on the same devices.

In your situation you should look into providing load-balancing and redundancy using a routed solution, e.g. run a dynamic routing protocol with each of your providers, and load-balance on Layer 3.

HTH, Thomas

wim_depauw Tue, 10/07/2008 - 06:30
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I think there is a misunderstanding .

The providers gives us a wire and this is actually a long ethernet cable. For example we can see the cisco devices at the other side with CDP. If there is a ( Cisco) device of the provider in between then this should not be possible.

In belgium this type of connection is known as a BLES. I think you can see it as a MAN connection.

To conclude: It is a pure L1 connection

tcordier Tue, 10/07/2008 - 06:57
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You still have this type of setup:

YourSwitchPort1 -----ETH----- Provider1Switch

YourSwitchPort2 -----ETH----- Provider2Switch


In this case you can not build an Etherchannel since this requires a single remote switch.

You can by the way tunnel CDP over VLANs, which allows you - as customer - to see your remote switch as CDP neighbor although there are intermediate provider switches.

Let me know if I misunderstood the setup.

Regards, Thomas

Kevin Brennan Tue, 10/07/2008 - 07:53
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Hi Wim,

I have 2 x 100Mb metro ethernet circuits like yours (CDP works over them and they are effectively "long fast ethernet" cables)

The circuits are from two different SP's. Initially I did try etherchanneling them using single switches on both sides, but the channel always failed with weird errors. I think Etherchannel really is just meant for local area setups.

I ended up using 2 x 3560's with IP Services IOS at both ends as high speed routers and then ran eigrp as my routing protocol. I simply used a /30 network between the sites.



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