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industrial communications handbook 2016
it may be necessary to reconfigure some software to
work with the new ranges—such as SCADA and other
monitoring or control software—as well as firewall and
routing configurations.
6.7 Routing
Routing is directly and intrinsically related to the IP
structuring on the network. On a Greenfield project de-
signing routing is similar to designing the IP structuring
for the network. The same information is required as for
designing IP structures (list of devices and segregation
framework), as well as a list of what devices need to
intercommunicate with each other. From here, it be-
comes simple matter of planning out the routing table
and configuring the routing rules on all the routers. In
some cases it may also be possible to clean up the rout-
ing tables by super-netting multiple IP ranges together,
depending on the network design.
In an existing network that is being expanded, rout-
ing is similar to IP structure design, in that it can prove
to be extremely easy or monumentally hard. In some
cases it may be a simple case of adding a new route or
two to the routing table to cater for the new devices on
the network, whilst in others a complete redesign of the
network is required depending on the complexity of the
routing system. Furthermore, a redesign will require
reconfiguration of all end devices that require routing,
as their gateway IP address will need to be changed to
match the new network design. This again shows the
importance of correctly planning not only for the origi-
nal network in the starting phases, but also for future
upgrades and expansion.
6.8 Firewalls
A router is set up to move data between different sub-
nets. However, it only gives control over what data will
be routed where, not control over what data is allowed
to be routed where. For this, a firewall is required on
the network. Most industrial routers these days include
a firewall, but it is important to make the distinction
between the routing component of the device and the
firewall.
Setting up a firewall on a mission-critical site is
closely tied in with the router setup, and since both are
performed together, the firewall setup follows a similar
pattern to the routing setup when viewed from a Green-
field/non-Greenfield perspective. On an expanding net-
work, if we have originally catered correctly for the ex-
pansion, firewall setup will involve either setting up a
few new rules on an existing firewall, or implementing a
completely new firewall if none exists. Both options are
pretty straightforward as long as all the requirements
are clearly laid out. If the entire network needs to be
redesigned, the firewall will need to be reconfigured
entirely and this could be a time-drain and can cause
downtime on the mission-critical network.
On a Greenfield project, the firewall will also need
to be configured from scratch. As long as the previous
steps and all firewall requirements have been laid out
in a clear fashion, the actual configuration should not
take too long a period of time. Because firewalls (and
routing) are so closely tied in with the IP structure, the
amount of work that needs to be invested in the router
setup is largely dependent on the complexity and chang-
es on the IP structure of the network. However, as with
most other points, the ‘clean slate’ provided by a Green-
field project will generally provide time and production
savings, and also give the option of designing the net-
work to fit the application, rather than designing the ap-
plication to fit the network.
6.9 Less stress
Greenfield projects are almost always easier to work on
than existing networks, and if the benefits they provide
are understood and utilised, commissioning a stable
and secure network can be created from the get go. If
all steps are properly documented along the way, main-
taining this network should also prove to be straightfor-
ward. On the other hand, constantly making unplanned
changes and expansions on an existing network can
lead to a frustrating mess that constantly causes prob-
lems, especially if the changes are not properly docu-
mented. One of the most important considerations of
a Greenfield project, as has been stressed many times,
is to plan properly for future expansion and upgrades.
This will lead to time and production savings, as well as
greatly decreased frustration and stress for those who
are in charge of maintaining the network and attached
devices.