Transcript Inter VLAN routing

INTER VLAN ROUTING
Ferry Astika Saputra
Understanding Access and Trunk Interfaces
• Ethernet interfaces can be configured either as access
ports or a trunk ports, as follows:
 An access port can have only one VLAN configured on the
interface; it can carry traffic for only one VLAN.
 A trunk port can have two or more VLANs configured on the
interface; it can carry traffic for several VLANs simultaneously.
Sumber : www.cisco.com
What is inter VLAN routing
Traditional Inter VLAN Routing (1)
Router on a stick Inter VLAN Routing (1)
Router on a stick Inter VLAN Routing (2)
Router-on-a-stick is a type of router configuration
in which a single physical interface routes traffic
between multiple VLANs on a network.
The router interface is configured to operate as a
trunk link and is connected to a switch port
configured in trunk mode.
The router performs the inter-VLAN routing by
accepting VLAN tagged traffic on the trunk
interface coming from the adjacent switch and
internally routing between the VLANs using sub
interfaces.
Router on a stick Inter VLAN Routing (3)
Subinterfaces are multiple virtual interfaces, associated
with one physical interface.
These subinterfaces are configured independently
configured with an IP address and VLAN assignment to
operate on a specific VLAN.
Traditional Vs Router-on-stick (1)
Port Limits
 Physical interfaces are configured to have one interface per VLAN
on the network.
On networks with many VLANs, using a single router to
perform inter-VLAN routing is not possible.
Instead, you could use multiple routers to perform interVLAN routing for all VLANs if avoiding the use of
subinterfaces is a priority.
 Subinterfaces allow a router to scale to accommodate more VLANs
than the physical interfaces permit.
Traditional Vs Router-on-stick (2)
Performance
 Because there is no contention for bandwidth on separate physical
interfaces, physical interfaces have better performance when
compared to using subinterfaces.
 Traffic from each connected VLAN has access to the full bandwidth of the
physical router interface connected to that VLAN for inter-VLAN routing.
 When subinterfaces are used for inter-VLAN routing, the traffic being
routed competes for bandwidth on the single physical interface.
 On a busy network, this could cause a bottleneck for communication.
Traditional Vs Router-on-stick (3)
Access Ports and Trunk Ports
 Connecting physical interfaces for inter-VLAN routing requires that
the switch ports be configured as access ports.
 Subinterfaces require the switch port to be configured as a trunk
port so that it can accept VLAN tagged traffic on the trunk link.
Traditional Vs Router-on-stick (4)
Cost
 Financially, it is more cost-effective to use sub interfaces over
separate physical interfaces.
 Routers that have many physical interfaces cost more than routers
with a single interface.
 Additionally, if you have a router with many physical interfaces,
each interface is connected to a separate switch port, consuming
extra switch ports on the network.
 Switch ports are an expensive resource on high performance
switches.
Traditional Vs Router-on-stick (5)
Complexity
 Using subinterfaces for inter-VLAN routing results in a less complex
physical configuration than using separate physical interfaces, because
there are fewer physical network cables interconnecting the router to
the switch.
 On the other hand, using sub interfaces with a trunk port results in a
more complex software configuration, which can be difficult to
troubleshoot.
 If one VLAN is having trouble routing to other VLANs, you need to check to
see if the switch port is configured to be a trunk and verify that the VLAN is
not being filtered on any of the trunk links before it reaches the router
interface.
 You also need to check that the router subinterface is configured to use the
correct VLAN ID and IP address for the subnet associated with that VLAN.
Traditional Vs Router-on-stick (6)
Configuring Traditional Inter VLAN routing
(1)
Configuring Traditional Inter VLAN routing
(2)
Switch configuration
Configuring Traditional Inter VLAN routing
(3)
Router configuration
Configuring Traditional Inter VLAN routing
(4)
Configure router-on-a-stick inter VLAN
routing (1)
Configure router-on-a-stick inter VLAN
routing (2)
Configure router-on-a-stick inter VLAN
routing (3)
Troubleshooting inter VLAN routing –
switch issues (1)
Incorrect VLAN
Troubleshooting inter VLAN routing –
switch issues (2)
Not configure as a trunk
Troubleshooting inter VLAN routing –
switch issues (3)
No Redundant link
Troubleshooting inter VLAN routing –
router issues
Incorrect VLAN on a stick
Troubleshooting inter VLAN routing – IP
addressing issues (1)
Incorrect IP
Addressing
Troubleshooting inter VLAN routing – IP
addressing issues (2)
Incorrect
subnet mask