Siemens SIMATIC NET SCALANCE SC-600 - Routing Function; Routing; Vrrpv3

Technical basics
3.7 Routing function
SCALANCE SC-600 Web Based Management (WBM)
50 Configuration Manual, 10/2021, C79000-G8976-C475-03
3.7 Routing function
3.7.1 Routing
Introduction
The term routing describes the specification of routes for communication between
different networks; in other words, how does a data packet from subnet A get to subnet
B.
SCALANCE SC-600 supports the following routing functions:
• Static routing
With static routing, the routes are entered manually in the routing table.
• Router redundancy
With standardized VRRP (Virtual Router Redundancy Protocol), the availability of
important gateways is increased by redundant routers.
– VRRPv2
– VRRPv3
3.7.2 VRRPv3
Router redundancy with VRRPv3
With the Virtual Router Redundancy Protocol v3 (VRRPv3), the failure of a router in a
network can be countered. Version 3 of VRRP (RFC 5798) is based on version 2 (RFC
5798).
VRRP can only be used with virtual IP interfaces (VLAN interfaces).
Several VRRP routers in a network segment are put together as a logical group
representing a virtual router (VR). The group is defined using the virtual ID (VRID).
Within the group, the VRID must be the same. The VRID can no longer be used for other
groups in the same L2/Ethernet segment.
The virtual router is assigned a virtual IP address and a virtual MAC address. One of the
VRRP routers within the group is specified as the master router. The other VRRP routers
are backup routers. The master router assigns the virtual IP address and the virtual MAC
address to its network interface. The master router sends VRRP packets
(advertisements) to the backup routers at specific intervals. With the VRRP packets, the
master router signals that it is still functioning. The master router also replies to the ARP
queries to the virtual address.
If the virtual master router fails, a backup router takes over the role of the master router.
The backup router with the highest priority becomes the master router. If the priority of
the backup routers is the same, the higher MAC address decides. The backup router
becomes the new virtual master router.