How many of you really want to understand VPC?? I know many people who are interested to understand VPC but couldn't grab the concept itself. Just for the sake of understanding, I tried my best here to give you an idea behind the concepts of VPC. VPC is a very new concept introduced by Cisco. VPC is nothing but the Virtual Port-Channel.
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| Single Connect |
In earlier networking days, we use to connect the devices with single links. This link used to be the only link between 2 devices (we will say "Switches"). With a single link, the chances of failures are more.
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| Dual Connect |
So people started connecting 2 links between switches. It was just for the redundancy purpose, and hence we got 1 working link (active) and 1 non-working (passive) link. This passive link used to block all the data traffic with the help of STP. Which is nothing but the waste of bandwidth... or we can say "resources were sacrificed, just for redundancy"
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| Port-Channel |
People spent there nights, to find how to use this extra connection between the switches? And the next step was, to bundle both the links logically. So now we got 2 physical links between 2 switches.... and both the physicals links are logically bundled together. Which is called as a Port-Channel.
Okk, now we got 2 active links between the switches.
But what if one of the switch fails? Can I connect my multiple switches together with a single logical link?? Is it possible?? Can I create a virtual switch? ..... And the answer is YES.
So now with VPC (Virtual Port-Channel), I can connect multiple switches with many physical links. And all these physical links are bundled in a single logical link. Since its a single logical link, ALL LINKS ARE ACTIVE. There is no STP blocking. And hence, the technology is also referred as Multi-Chassis Port-Channel.
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| Fig. VPC |
Now with VPC, we got 2 physical switches, which are directly connected. Just as shown in above Fig. And both the switches are configured as a single logical switch. They represent themselves as a Single Logical Switch to all other switches connected to them. In other words, rest of the switches thinks that, they are connected to single switch. And all the links between the Virtual Switch and Other Switch are bundled together in a single port-channel, which is nothing but, our Virtual Port-Channel or VPC. A VPC can provide Layer 2 multipathing, which allows you to create redundancy and increase bidirectional bandwidth by enabling multiple parallel paths between nodes and it also allows load balancing traffic.
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