Let's be in a picture of what we're talking about. Let's say that we have a
pair
of distribution switches which connect to the network core and we have these
connecting down to several access closets. So we've got a set of closets each
with a switch here ahead and switch and we connect them all out. So maybe this
is a stack of switches at each location. So what we're going to do for SDA is
we are going to go ahead and build a fabric here. This fabric is actually going WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we are going to go ahead and build a fabric here. This fabric is actually going
to include the distribution switches here in the middle in the underlay.
Meaning
that these switches here are going to form the overlay with one another by
forming the X-land tunnels to one another and that's going to allow them to
communicate at layer two. In fact, let's go ahead and draw that just with a
different color so we can kind of see the difference here. And then we have
SVI's that are going to exist on each one of these switches and that allows us WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
SVI's that are going to exist on each one of these switches and that allows us
to let's say extend VLAN 10 across all of these switches this way and VLAN 20
will say is this set of SVI's and notice that they each have an SVI for each
one of the VLANs. So VLANs 10 and 20 here, 10 and 20 here, 10 and 20 here. This
is
the concept known as any cast gateways and we're going to talk about that in
more detail later on. Now what we have is we have a set of three fabric edge WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
more detail later on. Now what we have is we have a set of three fabric edge
nodes
in this environment. These fabric edge nodes are going to bring traffic in and
forward them to each other in order to allow network traffic to propagate. Now
if
we have a lot of east-west traffic meaning traffic within this access switch
domain, VLANs 10 and 20 in our case, then we're going to see a lot of use case
with the VX lands. And so a packet let's say comes in here on VLAN 10 and we WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
with the VX lands. And so a packet let's say comes in here on VLAN 10 and we
are
destined for a host that's connected to VLAN 10 but over here on this other
switch. What's going to happen? Well as we alluded to earlier we're going to
have
a control plane node that is part of the network and this control plane
node could be maybe an ISR that is hanging off of let's say the distribution
switch here. And so this switch, this fabric edge node is going to reach out WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
switch here. And so this switch, this fabric edge node is going to reach out
and
say hey I need that destination because I'm trying to get to whatever IP
addresses out here. This host that I'm trying to communicate with and I don't
know which of these other fabric edge nodes afford it to. And so we provide
the answer here we're going to send it to let's say switch two in this case and
that is the role of the control plane node. And so we encapsulate it in that VX
land tunnel and it goes from VLAN 10 on this side through the fabric across WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
land tunnel and it goes from VLAN 10 on this side through the fabric across
those
layer three boundaries but in a layer two tunnel and it's going to exit out of
switch two here and it's going to find its destination. So that is the role of
the control plane node and we see the fabric edge nodes that work here.
Meanwhile
what happens if we are destined for something else? Now we're talking about
north or something outside of the SDA fabric. And now we're talking about
needing to get to the rest of the network and so this would be the border WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
needing to get to the rest of the network and so this would be the border
nodes. Now we could make these distributions which is the border nodes and
fact if we're connecting to the network core then we probably wouldn't want to
do that. But for now let's say that we've just got a border node here maybe it
's a
network stack of switches maybe it's a router either way we have this border
node. Usually we'll have a pair for redundancy so I'll just say border nodes
here. And we've got connectivity through the underlight to the rest of the WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
here. And we've got connectivity through the underlight to the rest of the
fabric and now this is going to connect us out to the network core. So we see
that the fabric is within the scope of a single architecture. Maybe this is a
single site or a campus network that has a lot of access layer closets but it
really is encompassing this domain not the core and not everything that exists
that side of the core such as the WAN block and the internet block and all of
the other network blocks that are part of our hierarchical network WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
the other network blocks that are part of our hierarchical network
architecture. Well if a packet comes in and it's destined for something that
doesn't exist here in the SDA fabric while the control plane node is not going
to know then where that is. And so we're going to use the border node as this
sort
of default route in our SDA fabric and so we're going to forward that traffic
to
the border nodes and allow the border nodes to send it out to the non SDA WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
the border nodes and allow the border nodes to send it out to the non SDA
domain
and we hope that we get to the destination there. So meanwhile all of this is
being managed as we've said by our set of controllers over here. We're going to
have catalyst center. We're going to have ice integration. That would be the
identity services engine and this is going to be pushing our configurations and
pushing our policy out to the fabric to let everybody know how all of this WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
pushing our policy out to the fabric to let everybody know how all of this
traffic is meant to be forwarded and we as the admins we don't actually have to
log into all of these devices to make it happen. Instead we simply log into
catalyst center in order to add our own definitions for these configurations
and
policies. So that is a high-level view of how all this comes together. We see
that this diagram gets pretty busy when we're talking about all of the
different components of an SDA fabric but we also see how all of these node WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
different components of an SDA fabric but we also see how all of these node
types come together and how the controllers come together in order to make end
and traffic flow happen.