19. Virtual Switch Bridging
ROX™ v2.2 User Guide
184
RuggedBackbone™ RX5000
19. Virtual Switch Bridging
19.1. Overview
A virtual switch bridges different network segments in way that is not dependent on a particular protocol.
Network traffic between segments is forwarded regardless of the IP and MAC addresses in a packet.
In a virtual switch, forwarding is done in Layer 2 and allows all network traffic, including L2 Multicast
(GOOSE, ISO), IP Multicast, Unicast, and Broadcast messages, to go through the virtual switch tunnel
without any modifications. A virtual switch can be useful for GOOSE messaging when the sender and
receiver need to communicate through a routable IP network. Because there is no IP encapsulation
for the L2 traffic going through the virtual switch, network latency is minimized for the traffic between
end devices.
The virtual switch appears on the device as a virtual Ethernet interface over a physical interface
(Ethernet port) between two routers. Physically, the two routers can be in different locations. There can
be multiple virtual switch instances in a router. Each instance can include two or more interfaces, but
an interface can only be a member of one virtual switch instance.
A virtual switch interface in a router can be a routable interface when an IP address is assigned either
statically or via DHCP. The network address assigned to the virtual switch interface can be included
in the dynamic routing protocol and the interface can carry a routing update. The IP address assigned
to the virtual switch can be used as the default gateway for the end devices connected to the virtual
switch interface. Network services, such as SSH, DHCP, NTP, VRRP, etc, can be configured to run
on the virtual switch interface.
19.1.1. Helpful Hints
• Be careful when adding a VLAN interface (assigned to a switch port on a given line module) in the
virtual switch. The VLAN tag on a tagged frame received on the VLAN Interface of a switch port
may not be preserved when the traffic is egressed through a routable interface (FE-CM-1, FE-EM-1)
which is also part of the same virtual switch instance. However, a VLAN tag is preserved when tagged
traffic is received on a routable interface. See
Section 19.2, “Sample Use Case”
configuring a virtual switch that includes a switch port and a router port.
• Any IP address assigned to an interface becomes inactive and hidden when the interface is added
to the virtual switch. The address on the interface is reactivated after removing the interface from
the virtual switch.
• Be careful when adding interfaces to the virtual switch. Any network services running on the individual
interfaces will need to be reconfigured after adding the interface to the virtual switch. For example, if
a DHCP server running on FE-CM-1 is subsequently made a member of the VirtualSwitch VS1, the
DHCP configuration must be changed to refer to VS1.
• In ROX™, the virtual switch is implemented in the software. Therefore, a CPU resource is needed to
perform forwarding of broadcast, multicast and unicast traffic.
• If the router is running as a firewall, the routeback option must be enabled for the virtual switch
interface in the “fwinterface” submenu under the Firewall menu.
