Technical information

ADC Telecommunications, Inc.
314 C
HAPTER 12: CONFIGURING IP ROUTING
Configuring IP Source Routing
IP source routing allows you to configure the default route a packet should
take based on the source IP address of the packet. This section provides
information and procedures about configuring IP source routing on the Cuda
12000 and includes following:
■ About IP Source Routing
■ Adding a Source Route
About IP Source Routing
Source routing allows you to configure a different default route for each IP
network or host. Specifically, source routing allows you to define the default
route (next hop gateway) to which a packet containing a particular source IP
address should be forwarded in the event that a local route to the
destination does not exist. This feature is called source routing because the
route is determined by the source of the message.
When an IP packet is received on an interface:
■ The interface performs a normal destination-based route lookup.
■ If the system finds no route, or if a default route exists for the destination
IP address, it then checks the source routing entries defined on the
interface.
■ If the system finds a source routing entry defined for the source address,
the packet is forwarded to the next hop gateway associated with the
source address. Otherwise, the default route defined in the routing table
is used.
This logic enables learned routes to take precedence over both default routes
and source routing entries; but enables source routing entries to take
precedence over default routes.
Source routing is configured on an interface on which you define these
source routing criteria:
■ Source IP address to match. An IP address and network mask
combination that allows you to define the source route to match as a
network, or scope it down to a specific host.