Nortel Networks 42C4911 Switch User Manual


 
Alteon OS Application Guide
Chapter 8: Basic IP Routing
14742C4911, January 2007
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 GbE Switch Module, routing between different IP sub-
nets 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 auto-
matic frame conversion allows servers to communicate using Jumbo frames, all transparently
to the user.