Contents as access ports. sub interfaces need the

Contents
VLANS  Advantages and Disadvantages. 2
VLANs allow logical
grouping of end-device that are physically isolated on network. 2
With VLANs there is
no need to have more routers deployed on the network to contain broadcast
traffic. 2
Quarantine of
broadcast domains on network reduces traffic. 2
Limits of ports. 2
Performance. 2
Access and Trunk Ports. 2
Trunking concepts. 2
Frame Tagging. 2
Security in VLAN.. 3
(ARP) attack. 3
Double Encapsulation/ Double Tagging VLAN Hopping Attack. 3
Cisco Discovery Protocol (CDP) Attack. 3
Multicast Brute-Force Attack. 3
Sub-Interfaces. 3
VTP Types. 4
VTP Modes. 4
Router-Switch Topology. 4
Designing the lab. 4
Configuration files. 6
Testing the configuration and show commands. 16
References: 40
 

 

 

VLANS Advantages and Disadvantages

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VLANs provide many
advantages such as easy administration reduces broadcast traffic and prosecution
of security policies.

VLANs allow logical grouping of end-device that
are physically isolated on network

With VLANs there is no need to have more
routers deployed on the network to contain broadcast traffic.

Quarantine of broadcast domains on network reduces
traffic.

Limits of ports

Physical interfaces are configured to have 1 interface in VLAN. On
networks with more than 1 VLAN using single router to achieve inter-VLAN
routing isn’t possible.
Sub interfaces allow router to scale to house more VLANs than
the physical interfaces.

 

Performance

Because there is no contention for bandwidth on physical interfaces. In busy
network this cause bottleneck for communication.

 

Access
and Trunk Ports

Connecting physical interfaces for inter-VLAN routing needs that the
switch ports be configured as access ports.
sub interfaces need the switch port to be configured as trunk port so
that it can take VLAN tagged (ISL or 802.1Q) traffic on the trunk link.

 

Trunking
concepts

In
the context of Ethernet VLANs use the term Ethernet trunking to mean carrying
multiple VLANs over single network link through the use of trunking protocol.
To allow for many VLANs on single link frames from distinct VLANs must be recognized.
The most common method IEEE 802.1Q adds tag to the Ethernet frame labeling it
as belonging to certain VLAN. Cisco also has proprietary trunking protocol
called Inter-Switch Link which encapsulates Ethernet frame with its container which
labels frame as belonging to specific VLAN.

Frame
Tagging

Frame tagging is used to
identify the VLAN that the frame belongs to in network with many VLANs. The
VLAN ID is located on the frame when it reaches switch from access port. That
frame can then be forwarded out the trunk link port. Each switch can see what
VLAN the frame belongs to and can forward the frame to equivalent VLAN access
ports or to another VLAN trunk port.

Two trunking
protocols are used today for frame tagging:

·        
Inter-Switch
Link (ISL) – Cisco’s exclusive VLAN tagging protocol.

·        
IEEE
802.1q – IEEE’s VLAN tagging protocol. Since it is open standard it can be used
for tagging between switches from different brands.

 

Security
in VLAN

there
are several security vulnerabilities in Vlans.

 (ARP) attack

If host broadcasts ARP request to the network only
the applicable host reply. This let the attacker to sight traffic on the way
out of the network.  The attacker wants to broadcast the address of the device
they are trying to attack on the LAN to get the gateway to send the received
packets to himself before spreading them to the target. it can see all the
traffic received and outbound. one reflection is that without VLAN this
attacker might affect the complete LAN VLANs do alleviate this sort of
attack.  Additional way of justifying these ‘Man in the Middle Attack’ is
to use Secluded VLANs to force hosts to only connect to the gateway.

Double Encapsulation/ Double Tagging VLAN Hopping Attack

This is Switch Spoofing systems are now configured
properly to avoid Switch Spoofing.  building packet with 802.1Q VLAN headers. 
The 1st router strips off the 1st header and sends it on to second router. 
Router 2 strips the second header and send the packet to the end point. 
It works only if the trunk has the same native VLAN as the attacker.  To avoid
this attack disable auto-trunking and use devoted VLAN ID for all trunk ports.

Cisco Discovery Protocol (CDP) Attack

CDP is feature that permits Cisco devices to
exchange information and configure the network to work easily together. 
The information sent is sensitive such as router models IP addresses software
versions.  It is all sent in plain text so any attacker sniffing the
network is able to get this information and it is possible to impersonate
another host. disable CDP to avoid this.

Multicast Brute-Force Attack

multicast brute-force attack hunts for faults
in switch software.  The attacker attempts to exploit any possible weakness
in switch by attack it with multicast frames.  with CAM overflow the goal
is to see if switch getting huge amount of layer 2 multicast traffic will “disobey”. 
switch should limit the traffic to its own VLAN but if the switch doesn’t handle
this properly frames may leak into another VLAN if routing connects them. 
The switch should contain all the frames within their proper broadcast domain
and attack of this nature shouldn’t be conceivable.  However, switches
have disastrous to handle this form of attack in the past and henceforth it is additional
attack vector.

Sub-Interfaces

sub-interface is logical interface that uses
the “parent” physical interface for moving the data. 
If we had router with only 1 physical interface but need to have the router
connected to 2 IP networks so that it could do routing we could create 2
logical sub interfaces assign each sub interface IP address within each subnet and
we can route between it.
Creating the sub interfaces on the routers we tell the router which VLAN to
associate with that sub interface in the same line as the encapsulate command

VTP
Types

VLAN
Trunk Protocol (VTP) reduces management in switched network. When we configure new
VLAN on 1 VTP server the VLAN is spread through all switches in the domain.
This decreases the need to configure the same VLAN everywhere. VTP is Cisco-proprietary
protocol.

VTP Modes

You can configure switch to operate in any of
these VTP modes:

·        
Server: In this
mode we can create delete and modify VLANs and specify further configuration
parameters for the entire VTP domain. VTP servers advertise their VLAN
configuration to other devices in the same VTP domain and synchronize VLAN
configuration with other switches based on advertisements received from trunk
links. default mode is VTP server.

·        
Client: VTP
clients act the same way as VTP servers but we cannot create or change or
delete VLANs on VTP client.

·        
Transparent: VTP
transparent switches don’t participate in VTP. VTP transparent switch doesn’t advertise
its VLAN configuration and doesn’t synchronize its VLAN configuration based on
received advertisements.

Router-Switch
Topology

 

Designing
the lab

 

Diagram
1

 

 

 

Configuration files

There
are the config of all routers and switches in the topology:

Umabelh Router

!

version 12.2

no service
timestamps log datetime msec

no service
timestamps debug datetime msec

no service
password-encryption

!

hostname
Umabelh

!

interface
Loopback0

 ip address 172.16.200.1 255.255.255.252

!

interface
FastEthernet0/0

 ip address 17.16.4.1 255.255.255.0

 duplex auto

 speed auto

 no shutdown

!

interface
FastEthernet0/1

 no ip address

 duplex auto

 speed auto

 shutdown

!

interface
Serial0/0

 ip address 172.16.100.2 255.255.255.252

 clock rate 9600

!

interface
Serial0/1

 no ip address

 shutdown

!

router eigrp 10

 network 172.16.100.0 0.0.0.3

 network 172.16.200.0 0.0.0.3

 network 172.16.4.0 0.0.0.255

 no auto-summary

!

ip classless

!

!

line con 0

line vty 0 4

 login

!

!

!

end

 

 

 

 

 

Alkuwair Router

 

!

version
12.2

no
service timestamps log datetime msec

no
service timestamps debug datetime msec

no
service password-encryption

!

hostname
Alkuwair

!

interface
FastEthernet0/0

 no ip address

 duplex auto

 speed auto

!

interface
FastEthernet0/0.1

 encapsulation dot1Q 1 native

 ip address 172.16.1.1 255.255.255.0

!

interface
FastEthernet0/0.10

 encapsulation dot1Q 10

 ip address 172.16.3.1 255.255.255.0

!

interface
FastEthernet0/0.20

 encapsulation dot1Q 20

 ip address 172.16.2.1 255.255.255.0

!

interface
FastEthernet0/1

 no ip address

 duplex auto

 speed auto

 shutdown

!

interface
Serial0/0

 ip address 172.16.100.1 255.255.255.252

!

interface
Serial0/1

 no ip address

 shutdown

!

router
eigrp 10

 network 172.16.1.0 0.0.0.255

 network 172.16.2.0 0.0.0.255

 network 172.16.3.0 0.0.0.255

 network 172.16.100.0 0.0.0.3

 no auto-summary

!

ip
classless

!

line
con 0

line
vty 0 4

 login

!

!

!

End

 

Switch1

 

!

version
12.1

no
service timestamps log datetime msec

no
service timestamps debug datetime msec

no
service password-encryption

!

hostname
Switch1

!

!

!

vlan
10

 name Staff

!

vlan
20

 name Student

!

interface
FastEthernet0/1

 switchport mode trunk

!

interface
FastEthernet0/2

 switchport mode trunk

!

interface
FastEthernet0/3

 switchport mode access

!

interface
FastEthernet0/4

!

interface
FastEthernet0/5

 switchport access vlan 10

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/6

 switchport access vlan 10

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/7

 switchport access vlan 20

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/8

 switchport access vlan 20

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/9

!

interface
FastEthernet0/10

!

interface
FastEthernet0/11

!

interface
FastEthernet0/12

!

interface
FastEthernet0/13

!

interface
FastEthernet0/14

!

interface
FastEthernet0/15

!

interface
FastEthernet0/16

!

interface
FastEthernet0/17

!

interface
FastEthernet0/18

!

interface
FastEthernet0/19

!

interface
FastEthernet0/20

!

interface
FastEthernet0/21

!

interface
FastEthernet0/22

!

interface
FastEthernet0/23

!

interface
FastEthernet0/24

!

interface
Vlan1

 ip address 172.16.1.2 255.255.255.0

!

ip
default-gateway 172.16.1.1

!

!

line
con 0

!

line
vty 0 4

 login

line
vty 5 15

 login

!

!

end

 

 

 

Switch 2

 

!

version
12.1

no
service timestamps log datetime msec

no
service timestamps debug datetime msec

no
service password-encryption

!

hostname
Switch2

!

!

!

interface
FastEthernet0/1

!

interface
FastEthernet0/2

 shutdown

!

interface
FastEthernet0/3

!

interface
FastEthernet0/4

!

interface
FastEthernet0/5

 switchport access vlan 10

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/6

 switchport access vlan 10

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/7

 switchport access vlan 20

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/8

 switchport access vlan 20

 switchport mode access

 switchport port-security

 switchport port-security mac-address sticky

!

interface
FastEthernet0/9

 shutdown

!

interface
FastEthernet0/10

 shutdown

!

interface
FastEthernet0/11

 shutdown

!

interface
FastEthernet0/12

 shutdown

!

interface
FastEthernet0/13

 shutdown

!

interface
FastEthernet0/14

 shutdown

!

interface
FastEthernet0/15

 shutdown

!

interface
FastEthernet0/16

 shutdown

!

interface
FastEthernet0/17

 shutdown

!

interface
FastEthernet0/18

 shutdown

!

interface
FastEthernet0/19

 shutdown

!

interface
FastEthernet0/20

 shutdown

!

interface
FastEthernet0/21

 shutdown

!

interface
FastEthernet0/22

 shutdown

!

interface
FastEthernet0/23

 shutdown

!

interface
FastEthernet0/24

 shutdown

!

interface
Vlan1

 ip address 172.16.1.3 255.255.255.0

!

ip
default-gateway 172.16.1.1

!

!

line
con 0

!

line
vty 0 4

 login

line
vty 5 15

 login

!

!

end

Testing the configuration and
show commands

There are snapshot from devices after applying previous
config and write the appropriate   show
command to ensure correctness of configs.

Umabelh Router

Serial
interface

Loopback
interface

Interfaces
and its ips:

 

EIGRP
routing protocol and assign connected networks:

The
routing table:

 

Alkuwair Router

 

Serial
interface

EIGRP
routing protocol and assign connected networks

The
routing protocol

 

Interfaces and sub interfaces
and its ips:

 

Switch1

 

Vlans
and assigning ports

Port
security on port f0/1

Port
security on port f0/5

 

Port
security on all ports

 

Port
security address

 

 

 

Vtp
status

Interface
vlan 1

Disconnect
pc and connect another pc

Shutdown
the port for port security

Switch2

 

 

 

Vtp
status

Interface
vlan 1

 

Pc connectivity

 

Test
the connection between all Pcs and networks

 

References:

Frame tagging explained

https://en.wikipedia.org/wiki/Trunking

https://library.netapp.com/ecmdocs/ECMP1196907/html/GUID-C9DA920B-F414-4017-8DD1-D77D7FD3CC8C.html

https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/10558-21.html

https://www.computernetworkingnotes.com/ccna-study-guide/switchport-port-security-explained-with-examples.html

Ten top threats to VLAN security

 

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