User guide

11-2 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
IP U
NICAST
R
OUTING
For more information on interior gateway protocols, refer to Chapter 12. For
information on exterior gateway protocols, refer to Chapter 13.
O
VERVIEW OF
IP U
NICAST
R
OUTING
The switch provides full layer 3, IP unicast routing. It exchanges routing information
with other routers on the network using either the Routing Information Protocol (RIP)
or the Open Shortest Path First (OSPF) protocol. The switch dynamically builds and
maintains a routing table, and determines the best path for each of its routes.
Each host using the IP unicast routing functionality of the switch must have a unique IP
address assigned. In addition, the default gateway assigned to the host must be the IP
address of the router interface.
R
OUTER
I
NTERFACES
The routing software and hardware routes IP traffic between router interfaces. A router
interface is simply a VLAN that has an IP address assigned to it.
As you create VLANs with IP addresses belonging to different IP subnets, you can also
choose to route between the VLANs. Both the VLAN switching and IP routing function
occur within the switch.
Each IP address and mask assigned to a VLAN must represent a unique IP
subnet. You cannot configure the same IP address and subnet on different
VLANs.
In Figure 11-1, a BlackDiamond switch is depicted with two VLANs defined; Finance
and Personnel. All ports on slots 1 and 3 are assigned to Finance; all ports on slots 2 and
4 are assigned to Personnel. Finance belongs to the IP network 192.207.35.0; the router
interface for Finance is assigned the IP address 192.206.35.1. Personnel belongs to the IP
network 192.207.36.0; its router interface is assigned IP address 192.207.36.1. Traffic
within each VLAN is switched using the Ethernet MAC addresses. Traffic between the
two VLANs is routed using the IP addresses.