Network with Only Static Routes?

[Matrix1]

Scenario: Small retail network running no internal routing protocols. Everything is statically routed at the firewall. Firewall has MPLS connection to remote offices and site-to-site VPNs over Internet to stores. Assuming I am a total network n00b, why is this setup bad? What is wrong with all my routes being static in a small environment??

[Georg Pauwen]

Hello,

nothing wrong with that, to the contrary, if you have just a small network, static routes are much easier to configure. Especially if you don't have the knowledge and/or expertise to configure (complex) routing protocols, it is a very good idea not to add them to your topology. Because if something goes wrong, you would have a hard time troubleshooting.

The only thing to keep in mind is that, in general, there is no redundancy with static routes.

[Joseph W. Doherty]

". . . why is this setup bad?"

According to who?

Of course, much might depend on how you define "small".    Besides number of routers, network topology impacts pros and cons of static routing vs. dynamic routing.

Personally, once you get beyond 3 or 4 devices, I believe using a dynamic routing protocol often eases maintenance, but there is an additional learning curve, and dynamic routing protocols have their own foibles.

Remember, perhaps the whole point of why dynamic routing protocols were developed is due to how poorly static routing "scales", again why how you define "small" can be important.

BTW, to clarify a point Georg raises, you can have redundancy with static routes, but that too also has a learning curve and another set of foibles.

[Richard Burts]

There are things that we do not know about this environment and that impacts our ability to give good advice. In particular we are told in general that this is a small network that is configured with static routing. We do not know whether there is any possibility of alternate paths to reach some destinations.

If each destination in the network has only a single path to get to it then static routes are adequate, and have less complexity and require less effort, and impose less network overhead. So static routes equal good.

But if some destinations in the network have an alternate path then a dynamic routing protocol has advantages because it can automatically detect failure of the primary path and automatically select the alternate path. With static routes some effort is required to detect failure of the primary path (typically something like IP SLA) and some effort is required to change the static route to the alternate path.

[Joseph W. Doherty]

BTW, what Rick (well) describes concerning the (network) environment is why I noted the network topology, not just the number of routers, is important determinate whether static or dynamic routing might be the better choice.

As an example of the impact of topology, let's begin with four routers in a star configuration, i.e. you have a hub router, with a single p2p link to three edge routers.  Each of those edge routers might have a static default route toward the hub.  The hub might then have a single static route toward the edge router which has one or more networks on its local side.  So, when adding/removing/changing networks, out on the edge, you'll only need to update the corresponding, single instance, of a static route on the hub router.

With this topology, even if you add additional edge routers, you still only need to maintain an instance of static routes on the central hub router.

However, if we replace that central hub router with a something like a switch (or some multi-point MetroE or VPNs), even with only three edge routers, changing a local network on one edge router may require changing static routes on the two other edge routers.  I.e. possible more work to maintain just three routers vs. the earlier four (or more).

With dynamic routing, we just add the network to the edge router, and it "informs" the other edge routers.

Of course, as we add edge routers, again, adding/removing/changing local networks also automatically informs the other routers; an example of possibly less maintenance then manually revising multiple routers' static route tables.

As Rick has also (well) said, as we don't know the particulars of your network, we're not in a position to suggest whether your network might be better served with static or dynamic routing, but in general, certainly there are networks, often small (and not complex) where not only is static routing not bad but may actually have more in its favor than dynamic routing.