Fujitsu PSWITCH 2048T User Manual page 127

User's Guide
I The default route learned on the routing interface takes precedence over
the default route learned on the management interface.
This product supports multiple routing tables and it is possible to install multiple
default routes. This product uses the policy routing function of Linux to overcome
administrative problems. In addition to the default routing table of the Linux IP
stack, a separate routing table is created for the network port (if included in the
build) and the service port (if included in the build). These tables are used for
outbound packets whose source IP address is the same as the service port or
network port IP address.
You can select the routing table using the source IP address of the packet.
 If the packet is sent over a TCP connection and the TCP connection is initiated
remotely, the source IP address of the packet will always be the IP address that
was the target of the TCP connection. For example, if the user accesses the
router via SSH from 10.1.1.1, the source IP address of the packet sent back to the
SSH client is 10.1.1.1.
 For management traffic (such as ping and traceroute), you can use software to
set the source IP address. When the administrator sets the source address, the
software binds the socket used to send the packet to that source address. The
bind operation sets the source address before the route lookup.
The routing table for the default route on the network and service port is separate,
but the default route selected by the software is installed in the default Linux
routing table even though the default route is associated with the network or
service port. This is important to maintain compatibility with earlier release
behavior even if packets are sent consciously without a source IP address
configured.
This product applies the following logic using the new routing table created for the
service port and network port.
 When the transmission source IP address of the transmission packet is the
address on the service port:
- Use the routing table associated with the service port.
 When the source IP address of the transmission packet is the address on the
network port:
- Use the routing table associated with the network port.
 If neither:
- Use the default routing table.
This product creates a network port routing table by sending one Netlink message
December/2018
FUJITSU PSWITCH
127