Software Forwarding; Static Routing - Fujitsu PSWITCH 2048T User Manual

FUJITSU PSWITCH User's Guide
to the kernel. The software sends another Netlink message to the kernel to add a
default route to the routing table of the network port. If the default route for the
network port associated with the network port is not set or expired (DHCP), the
network port route table is deleted.
Like the network port routing table, a routing table for the service port is created.

3.1.9.11. Software Forwarding

Most unicast IP data packets are transferred in hardware, but there are exceptions
that require software transfer. For example, the case where the next hop IP address
of the packet is not resolved to the MAC address. In this case, the hardware traps
the packet to the CPU. The software application software, not the IP stack, forwards
these IPv4 packets. The software searches the destination IP address of the packet
in the unicast routing table, selects the next hop if the optimal route is an ECMP
route, and retrieves the next hop IP address from the ARP cache. If the next hop
has not yet been address resolved, ARP sends an ARP request and queues up to
three packets to that destination until an ARP response is received. The software
forwarding path does not fragment IPv4 packets that are larger than the IP MTU on
the outgoing interface. IPv4 packets larger than the IP MTU are discarded and an
ICMP destination unreachable message is sent to the source of the data packet.
IPv4 packets sent by the router follow different paths. Applications typically send
these packets to the socket via the IP stack. The IP stack forwards these packets
using its own routing table, which contains the routing table routes. The NO_ARP
flag is set in the routing interface, and the IP stack sets the destination MAC
address to all zeros. The software uses the ARP cache to enter the destination MAC
address before sending the packet.
The IP stack's routing table includes all routes from the unicast routing table and
routes associated with the out-of-band management interface. The management
route contains the local route of the IP address assigned to the management
interface and possibly the default route. The software does not install multiple
default routes into the routing table of the IP stack. If there is a default route in the
unicast routing table and the management interface has a default route, the
routing table default is installed on the IP stack.

3.1.9.12. Static Routing

Network administrators can configure static unicast routes. Static routes with the
same destination prefix and route priority are combined into the ECMP route. The
software installs a static route in the routing table only if the next hop IP address is
128 December/2018