Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 39)

Brocade Virtual ADX Switch and Router Guide 25
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Overview
3
Integrated Switch Routing (ISR)
The Integrated Switch Routing (ISR) feature enables VLANs configured on Virtual ADX Layer 3
Switches to route Layer 3 traffic from one IP subnet to another. Normally, to route traffic from one
IP subnet 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, are on the
same device.
ISR eliminates the need for an external router by allowing you to route between VLANs using virtual
routing interfaces (ve). 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 is 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.
All the ports within an IP Subnet VLAN must be in the same port-based VLAN. The IP Subnet VLAN
cannot have ports in multiple port-based VLANs, unless the ports in the port-based VLAN to which
you add the IP Subnet VLAN are 802.1q tagged.
You can configure multiple IP Subnet VLANs within the same port-based VLAN. In addition, a port
within a port-based VLAN can belong to multiple VLANs. For example, if you have a port-based VLAN
that contains ports 1 – 3, you can configure port 2 as a member of more than one IP Subnet.
IP subnet VLANs
For IP, 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.
The Virtual ADX routes packets between VLANs at Layer 3. To configure an IP subnet VLAN to route,
you must add a virtual routing interface to the VLAN, then configure the appropriate routing
parameters on the virtual routing interface.
NOTE
The Layer 3 Switch routes packets between VLANs of the same protocol. The Layer 3 Switch cannot
route from one protocol to another.
Default VLAN
By default, all the ports on a Virtual ADX are in a single port-based VLAN. This VLAN is called
DEFAULT-VLAN and is VLAN number 1.
Figure 2 shows an example of the default Layer 2 port-based VLAN.