Blade ICE G8000 manual Example of Subnet Routing, 2Switch-Based Routing Topology

RackSwitch G8000 Application Guide

Example of Subnet Routing

Consider the role of the G8000 in the following configuration example:

Default router: 205.21.17.1

IF 2

VLAN 2

Server subnet 1: 100.20.10.2-254

10GbE (port 49)

IF 1

VLAN 1

IF 4

VLAN 4

IF 3

VLAN 3

Server subnet 3: 206.30.15.2-254

Server subnet 2: 131.15.15.2-254

Figure 8-2Switch-Based Routing Topology

The switch connects the Gigabit Ethernet and Fast Ethernet trunks from various switched sub- nets 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.

BMD00041, November 2008 Chapter 8: Basic IP Routing „ 123