Example Of Subnet Routing - Lenovo RackSwitch G8264 Application Manual

Example of Subnet Routing

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Consider the role of the G8264 in the following configuration example:
Figure 40. Switch‐Based Routing Topology
IF 2
VLAN 2
Server subnet 1:
100.20.10.2-254
The switch connects the Gigabit Ethernet and Fast Ethernet LAGs 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
IF 1
VLAN 1
IF 3
VLAN 3
Server subnet 2:
131.15.15.2-254
IF 4
VLAN 4
Server subnet 3:
206.30.15.2-254
Chapter 26: Basic IP Routing
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