IBM RackSwitch G8000, Application Manual

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RackSwitch G8000: Application Guide
Example of Subnet Routing
Consider the role of the G8000 in the following configuration example:
Figure 19. Switch-Based Routing Topology
The switch connects the Gigabit Ethernet and Fast Ethernet trunks from various
switched subnets throughout one building. Common servers are placed on another
subnet attached to the switch. A primary and backup router are attached to the
switch on yet another subnet.
Without Layer 3 IP routing on the switch, cross-subnet communication is relayed to
the default gateway (in this case, the router) for the next level of routing intelligence.
The router fills in the necessary address information and sends the data back to the
switch, which then relays the packet to the proper destination subnet using Layer 2
switching.
With Layer 3 IP routing in place on the switch, routing between different IP subnets
can be accomplished entirely within the switch. This leaves the routers free to
handle inbound and outbound traffic for this group of subnets.
Default router:
205.21.17.1
Server subnet 1:
100.20.10.2-254
Server subnet 2:
131.15.15.2-254
Server subnet 3:
206.30.15.2-254
IF 1
VLAN 1
IF 2
VLAN 2
IF 3
VLAN 3
IF 4
VLAN 4