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I'm struggling in connecting two Windows 7 PCs (each with a 2 port Intel NIC) via two complete redundant paths. And I want to make it transparent to the services on that system. I was thinking on creating a Ethernet bridge on both NICs on each system and connect both lanes with separate switches. 

.-----------.       1                       3     .-----------. 
|       [NIC1]-------------[Switch1]-------------[NIC1]       |
| PC1   |br0 |                                   | br0|   PC2 | 
|       [NIC2]-------------[Switch2]-------------[NIC2]       |
.-----------.       2                       4     .-----------.

But I don't know if it is a valid approach. I've already read into Link Aggregation (IEEE 802.3ad/802.1x) with LACP but to my understand doesn't apply cause this won't work across separate switches. I've read further and found Shortest Path Bridging (IEEE 802.1aq) but couldn't figure out if this even applies to the scale of make 2 Windows 7 PCs communication redundant (it looks to be on the scale of datacenters).

And I was wondering if this doesn't work with simple ethernet? In this scheme above, what would happen if I pull the power plug on Switch1? Will the TCP connections on this ethernet setup figure it out? Or what do I have to do to ensure that this setup with redundant switches actually works?

Guaranteeing that every single IP packet arrives is not important, important is to detect the faulty equipment fast enough and stop using it, so that the TCP above survives and can handle the retransmits. Can this work or what is the best way to do it?

EDIT: the switches to my understanding are not stackable.

EDIT2: there is probably more than on PC1 trying to reach PC2 using a redundant Ethernet path covering switch1 and switch2.

Thank you!

Hhut
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1 Answers1

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LACP is the most popular way to do this nowadays since it allows for total bandwidth aggregation and link redundancy. However you rightly point out that you cannot do this with two separate switches, unless they can be stacked together to form a single logical switch.

A lot of intel NIC's provide several options in the driver / management application for link bonding/redundancy. One of which is a typical active/passive set up where one link is active until it fails, in which case the second link comes live. This is a sensible option if you are unable to do LACP.

All of these methods create a virtual NIC on the device which the operating system interfaces with and therefore the underlying set up is transparent to your applications.

tomstephens89
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  • Thank you! I've learned that when using Windows 7 Mac Bridge Feature the network bridge does support Spanning Tree Protocol which seems to do exactly what I want? Wouldn't this cover the redundancy aspects more precisely than using LACP? – Hhut Aug 28 '15 at 08:26
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    Spanning tree would work but its dependant on it being implemented properly on your switches. This is also not NIC bonding, the NIC's operate independently of each other and it is the switches job to detect loops and shutdown the interfaces that are parallel links. Only bridges & switches are relevant to spanning tree. I always see spanning tree as a method to protect against storms on the network caused by people plugging cables in where they shouldn't be. Bonding, whether it be LACP, or nic driver implemented active/passive is the correct way to handle link redundancy in my opinion. – tomstephens89 Aug 28 '15 at 17:06
  • Thank you. I'm trying to figure that out—of using Windows Mac ethernet bridging or teaming functions from the PROSET tools of my Intel NICs is preferable here. Since I've read a Windows Ethernet bridge behaves exactly like a switch with STP. The situation is probably not that complex since it only covers two switches but I haven't understood all the underlying conditions (but there are more than one PC1 probably). LACP won't work cause the redundant links should cover both switches and without some sort of bonding or teaming adapter, it is not transparent to the running application services. – Hhut Aug 30 '15 at 11:06