Static Routes

  • Thread starter Thread starter CK Lam
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C

CK Lam

Maybe this is a stupid question: but why do I need to
enter Default Gateway at the interface card for static
routes that I create in RRAS?

Example:

Subnet 1 ----RRAS A---Subnet 2---RRAS B---Subnet 3

In this case, for RRAS A, it is not enough just to have a
static route for Subnet 3 via RRAS B - I need to add a
default gateway setting for the NIC in Subnet 2 of RRAS A
that points to RRAS B.
 
Basic static routing works fine with one router. But once you have a
second router it gets harder. eg this works fine

192.168.1.x dg 192.168.1.1
|
192.168.1.1 dg blank
router
192.168.2.1 dg blank
|
192.168.2.x dg 192.168.2.1

All traffic which isn't "local" (ie same subnet) is sent to the router,
which delivers it in the other subnet.

But this fails with an extra router. To get from one end to the other
requires two hops in both directions. (Remember you must have a return route
for the reply packets). Both routers need to know where the outer subnets
are. They know about one (because they have an interface in it) but not
about the other.

192.168.1.x dg 192.168.1.1 Subnet A
|
192.168.1.1 dg blank
router1
192.168.2.1 dg ?
|
192.168.2.x dg ? Subnet B
|
192.168.2.254 dg ?
router2
192.168.3.1 dg ? Subnet C
|
192.168.3.x dg 192.168.3.1

What do you do about the default gateway setting of the clients in the
middle? If you make it 192.168.2.1 routing works between A and B, but fails
between B and C. If you make it 192.168.2.254, the opposite thing applies.

So what routing you need on the routers depends on which way this is
set. If you use default routing in one direction, you need a static route to
get the traffic through in the other direction.
 
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