Is Static Routing Necessary?

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Aug 24th, 2009
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I'd like to use an 1812 to route data between 2 subnets (say 10.1.1.x and 11.1.1.x). I'm setting up the two WAN interfaces (FastEthernet0 and FastEthernet1) with IP addresses and subnet masks for each of the two subnets.

Will traffic heading from the 10.1.1.x subnet and destined for the 11.1.1.x subnet automatically route correctly (and vice-versa), or will I need to configure static routing?

Also, a follow-up question. If I'm only expecting traffic from one of the subnets and destined to the other (either 10.1.1.x to 11.1.1.x, or vice-versa), do I need to configure a default route? If no default route is configured, what happens if a packet comes in destined for an unknown subnet?

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Richard Burts Mon, 08/24/2009 - 14:15
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In the situation which you describe where the router has 2 interfaces and networks are configured on each interface, then you do not need static routing to route between those networks.

In this situation I do not see any reason to configure a default route. The default route is certainly not needed to route between those networks. And if a packet came into the router and the destination were on some network not connected to the router, what could you do? Do you have any way to forward packets to any other network? As you describe it there is no benefit for a default route. And in this situation if a packet did come in with a destination for an unknown subnet, then the only thing that the router can do is to drop the packet.



Lucien Avramov Mon, 08/24/2009 - 23:32
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The only reason why you would need static or dynamic routes is for subnets that the router does NOT know about.

Nothing in this case in your scenario.

Fraser Reid Mon, 08/24/2009 - 23:56
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Just remember to give your devices a default gateway (the router interface closest to them)


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