In this lesson, we're going to explore
the Routing Redundancy Protocols.
Now, Routing Redundancy Protocol is a network protocol
that prevents disruptions in communication
by automatically rerouting data traffic in case of a path
or device failure to help ensure
the continuous network availability
and reliability are going to be maintained.
Now, while there are many routing redundancy protocols used
in our networks, like the Hot Standby Router Protocol,
the Virtual Router Redundancy Protocol,
and the Gateway Load Balancing Protocol,
all of these are typically grouped up together
under the name of a First Hop Redundancy Protocol.
Now, the First Hop Redundancy Protocol,
also known as FHRP,
is a set of protocols that are designed
to ensure network reliability
by providing automatic failover
to a backup router, in case the primary router fails,
in order for you to maintain uninterrupted network services.
Now, let me provide you with an analogy
to help solidify this concept.
Let's pretend that you're driving on the highway
and suddenly a lane is closed
due to some ongoing construction work.
Thankfully, your city has already been smart enough
to provide some signs and some alternative routes,
so you can easily navigate around
that construction without any significant delays
to your commute, and so you'll be able
to arrive to work on time.
Now, this is exactly what the First Hop Redundancy Protocols
do for us inside of our networks,
because they're designed to ensure
that even if a primary path is unavailable,
the network traffic can easily be dynamically routed over
another path to help ensure the smooth
and uninterrupted communications
that are going to occur for our networks.
The First Hop Redundancy Protocols are able
to determine when a primary router or your first hop fails,
and then it immediately redirects the packets
to a standby router instead,
and that way the communications
will continue without any issues.
The First Hop Redundancy Protocol is going to provide us
with three main benefits, reliability, load balancing,
and seamless transitions.
First, we have reliability.
Reliability really is the cornerstone of our network design,
and incorporating a First Hop Redundancy Protocol
will help to ensure that our communications remain up
and running, even if a single router inside
that configuration fails,
because the First Hop Redundancy Protocol will simply
reroute that traffic around the failed router
inside of our networks.
Second, we have load balancing.
Now, the First Hop Redundancy Protocol
not only helps when a router fails completely,
but can also be configured
to distribute your network traffic across multiple routers
in order to prevent a single device from becoming
overwhelmed with too much traffic.
And this in turn will increase the efficiency
of our network communications.
Third, we have seamless transitions.
The First Hop Redundancy Protocol is designed to ensure
that data always continues to flow properly by making quick
and seamless transitions from sending data
to one failed router over by redirecting it
to a standby router instead, when the router fails.
This all happens seamlessly without your end users even
being aware of it, and this in turn leads to a better
and more reliable user experience.
Now, to make the First Hop Router Redundancy Protocol work,
we're going to rely on two critical components,
and these are the Virtual IP and the Subinterface.
Now, a Virtual IP is an IP address
that is not bound to a specific device,
but instead is going to be serving as a representative
for one or more devices inside of our network.
Now, in the First Hop Redundancy Protocol,
we're going to have the Virtual IP address as an address
that the devices in the network are going to use
as their default gateway.
This means that no matter which
of your physical routers is actively routing the packets
at any given time, your network devices
are always going to continue to send their packets
to this unchanging Virtual IP instead,
to ensure a smooth and uninterrupted network experience,
because the First Hop Redundancy Protocol
will then reroute the traffic from that Virtual IP
to the primary or secondary router based on which one is up
and available to handle your routing needs at that time.
Now, a Subinterface on the other hand,
is designed to allow a single physical interface on a router
or switch to be subdivided into multiple logical interfaces.
Each Subinterface can be configured independently,
and each one can belong to different VLANs
with its own separate security policies
being attached to it.
This allows each Subinterface to have more autonomy
and to provide you with the ability
to provide more specific controls
to each of your Subinterfaces.
Subinterfaces are cost efficient,
and they help us when we're conducting
traffic management too.
This is because our Subinterfaces allow us to segment
and manage our networks without the need
for additional physical hardware.
And this in turn is going to help
to ensure a smoother data flow
and a more enhanced security posture.
Now, there are three main protocols that are considered
to be First Hop Redundancy Protocols.
These are known as the Hot Standby Router Protocol,
the Virtual Router Redundancy Protocol,
and the Gateway Load Balancing Protocol.
First, we have the Hot Standby Router Protocol.
The Hot Standby Router Protocol,
or HSRP, was first developed by Cisco
as a redundancy protocol
that can establish a fault tolerant default gateway
for your devices on a local network segment.
HSRP enables two or more routers to work together
by presenting the underlying devices
as a single virtual router
to the host on your local area network.
Inside of a Hot Standby Router Protocol configuration,
one router will be elected as the active router,
and it's going to be expected to handle
all the network's routing responsibilities.
While another one is designed as the standby router,
and it's going to wait to take over
at any time the active router fails in the future.
This transition will be seamless to your users,
and it helps to ensure
that minimum packet loss is going to be experienced
and that you don't have uninterrupted network services.
The Hot Standby Router Protocol also provides
a special feature known as preempting.
This is where a higher priority router
can take over as the active router if it comes online
after the initial election was made.
Second, we have the Virtual Router Redundancy Protocol.
The Virtual Router Redundancy Protocol,
also known as VRRP,
is a standard redundancy protocol that functions similarly
to the Hot Standby Router Protocol,
but there are a few key differences you should be aware of.
VRRP is considered to be an open standard,
unlike the more proprietary format of HSRP
that was developed by Cisco.
This means that since VRRP is an open standard,
it is not tied to a specific vendor,
and this allows for higher levels
of compatibility across multiple different brands
of networking equipment.
VRRP also enables the configuration of multiple routers
to act as a single virtual router with one designated
as the primary router and the other serving as backups.
If the primary router fails,
one of the backups will automatically take over
the primary router's role to ensure
that the network's default gateway remains available
to the hosts on that network.
The Virtual Router Redundancy Protocol also provides us
with a simple and automatic election scheme
that doesn't require any additional configuration
on the end user's devices too.
Third, we have the Gateway Load Balancing Protocol.
The Gateway Load Balancing Protocol, also known as GLBP,
is another Cisco developed protocol
that takes redundancy a step further
by adding load balancing capabilities into our mix.
Like HSRP and VRRP, the Gateway Load Balancing Protocol
is designed to allow multiple routers to provide redundancy
for the virtual IP address
that's assigned to the group of routers.
However, GLBP is uniquely designed
so that all of your configured routers
can simultaneously forward packet
in order to effectively distribute the traffic load
amongst all the routers in the group.
This is achieved by assigning
a different Virtual MAC address to each GLBP group member,
and the GLBP active virtual gateway will
then assign each of these addresses to clients,
so that multiple routers can share the traffic load
being handled on a given network.
The Gateway Load Balancing Protocol is great
at load balancing, of course, but it also does provide us
with redundancy like HSRP and VRRP do.
This is because the Gateway Load Balancing Protocol
will automatically redirect traffic
to other routers inside of the group
if any of those routers fail.
And this helps to ensure continuous network availability
while also optimizing our network's resource utilization.
So remember, routing redundancy protocols
are designed to provide us
with network reliability and efficiency.
Routing redundancy protocols
like the Hot Standby Router Protocol,
the Virtual Router Redundancy Protocol,
and the Gateway Load Balancing Protocol
are all going to work behind the scenes to ensure
that the data flow within our network will continue
to run even if a single router fails
during our daily network operations.
As we continue to depend on our networks
for everything from global communications
to streaming our favorite television shows,
ensuring router redundancy is really a critical aspect
of our network designs for both our home
and office networks.