Instructor: In this lesson,
we will learn about network errors.
Network errors are issues
that disrupt the normal flow of data across a network.
Network errors often occur
due to faults in configuration, hardware, or software.
Network error source types include switching errors,
routing errors,
as well as a virtual private network, or VPN,
and tunnel errors.
Switching errors occur when data packets
are misdirected or dropped.
Routing errors are when incorrect or inefficient paths
are chosen for data transmission across networks.
And finally, VPN and tunnel errors
are failures in establishing
or maintaining secure connections between networks.
Let's learn more about switching errors, routing errors,
as well as VPN and tunnel errors.
First, we have switching errors.
Switching errors occur when data packets are misdirected
or dropped as they move through a network switch.
Switching errors are typically caused by misconfigurations
or hardware issues within the switching infrastructure.
Three of the most common switching errors
include broadcast storms, VLAN mismatch,
and duplex mismatch.
Broadcast storms happen
when there is a layer 2 network loop,
which often occurs due to improper configuration
of the Spanning Tree Protocol, or STP.
STP is designed to prevent loops
by blocking redundant paths in the network.
But if STP is disabled or misconfigured, a loop can form.
This loop causes broadcast packets
to be endlessly forwarded between switches,
flooding the network with traffic and degrading performance.
For example, imagine two switches
connected by multiple links without STP enabled.
A broadcast packet is sent from one switch,
which will be replicated on all paths,
bouncing back and forth indefinitely.
This broadcast storm can cause packet loss, device crashes,
and network downtime
as legitimate traffic gets overwhelmed by excess broadcasts.
Next, VLAN mismatch is another common switching area.
Virtual local area networks, or VLANs,
segment network traffic,
isolating devices within specific broadcast domains.
A VLAN mismatch occurs
when two switches connected by a trunk
are configured with different VLAN settings.
For example, imagine two buildings in an organization
are connected by switches,
and the IT department has set up VLANs
to segment network traffic.
In building one, the switch is configured
to assign all office computers to VLAN 30
for internal communications.
However, in building two, the switch is incorrectly set
to assign the same types of computers to VLAN 40.
Because the VLAN configurations don't match,
the traffic between these two buildings
is dropped or misrouted.
This results in employees in the first building
being unable to access shared resources
like printers or file servers
located in the second building,
even though they are part of the same logical network.
This kind of VLAN mismatch can severely disrupt operations.
Finally, duplex mismatch is the last switching error
we will discuss.
Duplex mismatch occurs when two ends of a network link
have different duplex settings.
Duplex refers to how data flows between devices.
Full duplex allows data to be sent
and received simultaneously,
while half duplex only allows
send or receive at any one time.
A duplex mismatch happens
when one side of a connection is set to full duplex
and the other side is set to half duplex.
This misconfiguration leads to collisions
as the half duplex side tries to control the flow of traffic
while the full duplex side continues sending data.
This can cause severe performance issues
including packet loss, retransmissions,
and network slowdowns.
A practical example of this
would be a server connected to a switch
where the server's network card is set to full duplex,
but the switch port is configured for half duplex.
This mismatch would lead to poor communication
between the server and other devices on the network,
slowing down data transfers
and affecting the performance
of applications relying on this connection.
Second, we have routing errors.
Routing errors occur when incorrect or inefficient paths
are used for data transmission across networks.
Routing errors are typically caused by misconfigurations,
incorrect routing tables, or unstable network conditions.
Three of the most common routing errors
include routing loops, incorrect subnet masks,
and route flapping,
each of which can cause significant disruptions
in network performance.
Routing loops happen when a packet gets stuck
in a continuous cycle between routers
without ever reaching its destination.
This occurs due to misconfigured routing protocols
or improper route advertisements,
which create a loop in the network path.
For example, in a dynamic routing environment,
using a protocol like Routing Information Protocol,
if a router advertises a route back to the original sender
due to an outdated or incorrect routing table entry,
a packet could keep circling between routers indefinitely.
The mechanism that leads to this type of routing loop
is often triggered by slow route convergence
or a delay in propagating updated routing information.
For instance, if a network segment goes down
and a router doesn't yet know that a route is invalid,
it might continue advertising that route to its neighbors.
The neighboring routers, unaware of the failure,
update their tables
and send traffic back toward the failed route.
This process can create a loop
where routers keep sending the packet back and forth,
thinking the route is still valid.
Next, incorrect subnet masks
are another common routing error
and occur when the subnet mask associated with an IP address
is not configured correctly.
A subnet mask defines the network portion
and host portion of an IP address,
and when this is wrong,
routers can forward packets to the wrong subnet
or fail to forward them at all.
For example, if a device is assigned
to an IP address in the 192.168.1.0/24 network,
but mistakenly configured with a subnet mask of /16,
the router might try to route traffic
intended for the 192.168.2.0 network to the device,
causing connectivity issues.
This leads to problems where devices
that should be able to communicate within the same network
are isolated,
while routing tables
may incorrectly forward traffic to distant networks,
disrupting the flow of data.
Our last routing error is route flapping.
Route flapping refers to a situation
where a network route continuously changes its state,
going up and down frequently,
causing instability in the routing tables.
This can occur due to unstable network links,
faulty hardware,
or misconfigurations in the routing protocols.
When a router frequently advertises
that a route is available, then unavailable,
other routers must constantly update their routing tables,
leading to network instability.
For example, in an Open Shortest Path First,
or OSPF routing environment,
if a link becomes unstable
and repeatedly fluctuates between available and unavailable,
routers in the network will continuously
update their routing tables
to reflect the changing status of that link.
This constant recalculation takes time
and can lead to delays in packet forwarding,
increased network latency, and potentially dropped packets.
Our third and last type of network error
is VPN and tunnel errors.
Virtual private network, or VPN, and tunnel errors
occur when the encrypted communication tunnels
between different networks or endpoints
face disruptions due to misconfigurations,
expired credentials, or encryption failures.
Incorrect settings in VPN tunnels
can lead to connectivity issues
or failed connections between the client and the server.
VPN settings define critical parameters
such as IP addresses, tunnel types, routing rules,
and DNS configurations.
A misconfiguration in any of these settings
can prevent the VPN from functioning correctly.
For example, if a VPN tunnel is set up
with the incorrect IP address for the remote endpoint,
the client will attempt to send traffic
to the wrong destination,
and the tunnel will fail to establish.
This can be especially problematic
in large corporate environments
where VPNs are used to connect remote workers
to internal resources.
If the VPN settings are misconfigured,
employees may be unable
to access critical business applications,
leading to downtime and productivity loss.
Next, expired certificates are another common issue
that causes VPN tunnel errors.
Many VPNs rely on digital certificates
for mutual authentication between the client and the server,
ensuring that both sides are trusted.
Certificates have an expiration date,
and if not renewed in time,
they will cause authentication failures.
For example, if an organization uses certificates
for its site to site VPN,
and one of the certificates expires,
the VPN tunnel will no longer be able
to authenticate the devices on either end.
This will cause
the secure communication channel to break down,
leaving the network exposed to potential security risks.
So the regular monitoring of certificate expiration dates
and setting automated renewal processes
can help prevent this type of error.
Finally, issues with encryption protocols
can also disrupt VPN tunnels,
especially when outdated
or misconfigured protocols are in use.
VPN tunnels rely on encryption
to secure the data that passes through them
using protocols like Internet Protocol Security, or IPsec,
or Transport Layer Security, also known as TLS.
However, if there is a mismatch in the encryption algorithms
or keys used between the client and the server,
the tunnel will fail to establish.
For example, if one end of the VPN
is configured to use the Advanced Encryption Standard,
or AES encryption,
while the other end is set up
to use the Data Encryption Standard, or DES,
the encryption negotiation between the two ends will fail
and the tunnel will not be secured.
This can expose sensitive data
to interception during transmission,
so ensuring that both sides of the VPN
use strong and compatible encryption protocols
is essential for maintaining
a secure and reliable connection.
So remember, network errors disrupt
the flow of data across a network
and are often caused by misconfigurations, hardware issues,
and software bugs.
Common network errors include switching, routing,
and VPN or tunnel errors.
Switching errors occur when data packets are misdirected
or dropped due to issues like broadcast storms,
virtual local area network, or VLAN, mismatch
or duplex mismatch.
Routing errors such as routing loops,
incorrect subnet masks, and route flapping
lead to inefficient or disrupted data transmission.
Finally, virtual private network, or VPN,
and tunnel errors arise from incorrect settings,
expired certificates, or encryption protocol mismatches,
preventing secure communications.
Regular monitoring and proper configuration
help avoid these types of errors
and maintain network reliability.