HP 438031-B21 - 1:10Gb Ethernet BL-c Switch Application Manual page 106

Basic IP routing
Take a closer look at the HP 1:10GbE switch in the following configuration example:
Figure 15 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. Primary
and backup routers 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.
To make implementation even easier, UDP Jumbo frame traffic is automatically fragmented to regular
Ethernet frame sizes when routing to non-Jumbo frame VLANS or subnets. This automatic frame conversion
allows servers to communicate using Jumbo frames, all transparently to the user.
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