Integrated Switch Routing (Isr) - Dell PowerConnect B-RX Configuration Manual

11
Configuring virtual routing interfaces

Integrated Switch Routing (ISR)

Brocade Integrated Switch Routing (ISR) feature enables VLANs configured on the device to route
Layer 3 traffic from one protocol-based VLAN to another instead of forwarding the traffic to an
external router. The VLANs provide Layer 3 broadcast domains for the protocols, but do not in
themselves provide routing services. This is true even if the source and destination protocols 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). You configure a separate virtual routing interface on each VLAN that you
want to use to route packets. For example, if you configure two IP protocol VLANs on a device, you
can configure a virtual routing interface on each of the IP protocol VLAN, then configure IP routing
parameters for the IP protocol VLAN. Thus, the device forwards IP broadcasts within each VLAN at
Layer 2 but routes Layer 3 traffic between the VLANs using the virtual routing interfaces.
NOTE
The device uses the lowest MAC address on the device (the MAC address of port 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 (for example, interface ve 10). The logical interface allows the device
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 1/1 – 1/10, you
can configure port 1/5 as a member of an AppleTalk protocol VLAN, an IP protocol VLAN, and an
IPX protocol VLAN, and so on.
If the router interface for IP is configured on physical ports, then routing occurs independent of the
Spanning Tree Protocol (STP). However, if the router interfaces are defined for IP VLAN, they are
virtual routing interfaces and are subject to the rules of STP.
If your backbone is consisted of virtual routing interfaces all within the same STP domain, it is a
bridged backbone, not a routed one. This means that the set of backbone interfaces that are
blocked by STP will be blocked for routed protocols as well. The routed protocols will be able to
cross these paths only when the STP state of the link is FORWARDING. This problem is easily
avoided by proper network design.
When designing an ISR network, pay attention to your use of virtual routing interfaces and the
spanning-tree domain. If Layer 2 switching of your routed protocols (IP, IPX, AppleTalk) is not
required across the backbone, then the use of virtual routing interfaces can be limited to edge
switch ports within each router. Full backbone routing can be achieved by configuring routing on
each physical interface that connects to the backbone. Routing is independent of STP when
configured on a physical interface.
If your ISR design requires that you switch IP, IPX, or Appletalk at Layer 2 while simultaneously
routing the IP protocol over a single backbone, then create multiple port-based VLANs and use
VLAN tagging on the backbone links to separate your Layer 2 switched and Layer 3 routed
networks.
298 BigIron RX Series Configuration Guide
53-1002253-01