Dell FCX624-I Laptop User Manual


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432 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
VLAN overview
13
Integrated Switch Routing (ISR)
The Dell Integrated Switch Routing (ISR) feature enables VLANs configured on Layer 3 Switches to
route Layer 3 traffic from one protocol VLAN or IP subnet, IPX network, or AppleTalk cable VLAN to
another. Normally, to route traffic from one IP subnet, IPX network, or AppleTalk cable VLAN to
another, you would need to forward the traffic to an external router. The VLANs provide Layer 3
broadcast domains for these protocols but do not in themselves provide routing services for these
protocols. This is true even if the source and destination IP subnets, IPX networks, or AppleTalk
cable ranges are on the same device.
ISR eliminates the need for an external router by allowing you to route between VLANs using virtual
routing interfaces (ves). A virtual routing interface is a logical port on which you can configure Layer
3 routing parameters. You configure a separate virtual routing interface on each VLAN that you
want to be able to route from or to. For example, if you configure two IP subnet VLANs on a Layer 3
Switch, you can configure a virtual routing interface on each VLAN, then configure IP routing
parameters for the subnets. Thus, the Layer 3 Switch forwards IP subnet broadcasts within each
VLAN at Layer 2 but routes Layer 3 traffic between the VLANs using the virtual routing interfaces.
NOTE
The Layer 3 Switch uses the lowest MAC address on the device (the MAC address of port 1 or 1/1)
as the MAC address for all ports within all virtual routing interfaces you configure on the device.
The routing parameters and the syntax for configuring them are the same as when you configure a
physical interface for routing. The logical interface allows the Layer 3 Switch to internally route
traffic between the protocol-based VLANs without using physical interfaces.
All the ports within a protocol-based VLAN must be in the same port-based VLAN. The
protocol-based VLAN cannot have ports in multiple port-based VLANs, unless the ports in the
port-based VLAN to which you add the protocol-based VLAN are 802.1Q tagged.
You can configure multiple protocol-based VLANs within the same port-based VLAN. In addition, a
port within a port-based VLAN can belong to multiple protocol-based VLANs of the same type or
different types. For example, if you have a port-based VLAN that contains ports 1 – 10, you can
configure port 5 as a member of an AppleTalk protocol VLAN, an IP protocol VLAN, and an IPX
protocol VLAN, and so on.
IP subnet, IPX network, and AppleTalk cable VLANs
The protocol-based VLANs described in the previous section provide separate protocol broadcast
domains for specific protocols. For IP, IPX, and AppleTalk, you can provide more granular broadcast
control by instead creating the following types of VLAN:
IP subnet VLAN – An IP subnet broadcast domain for a specific IP subnet.
IPX network VLAN – An IPX network broadcast domain for a specific IPX network.
AppleTalk cable VLAN – An AppleTalk broadcast domain for a specific cable range.
You can configure these types of VLANs on Layer 3 Switches only. The Layer 3 Switch sends
broadcasts for the IP subnet, IPX network, or AppleTalk cable range to all ports within the IP subnet,
IPX network, or AppleTalk cable VLAN at Layer 2.
The Layer 3 Switch routes packets between VLANs at Layer 3. To configure an IP subnet, IPX
network, or AppleTalk cable VLAN to route, you must add a virtual routing interface to the VLAN,
then configure the appropriate routing parameters on the virtual routing interface.