From: Ya Wen (ywen@xxxxxxxxxxxxxxxxxxxxxx)
Date: Thu Apr 05 2001 - 14:45:13 GMT-3
George:
Please see in-line for answers:
On Thu, 5 Apr 2001, George Zhang wrote:
> I have configured OSPF and RIP redistribution. OSPF area 0 is configured
> between R2,R3,R4, and R5. They are connected through Frame relay, Hub-Spoke.
> R5 is the hub. Physical interfaces are used on all routers. In OSPF area 0,
> there are some /24, /26 and /30 networks, for example 170.150.5.0/24,
> 170.150.1.0/28, 170.150.3.0/30. R4 is connected to R6 through E0, the
> network is 170.150.46.0/24. RIP is configured on R4 and R6. Redistribution
> is configured between OSPF and RIP on R4.
>
> My questions are:
>
> Q1. The network between R2, R3, R4 and R5 is 170.150.1.0/28. Because of the
Frame
> relay configuration, I saw the following routes on R4:
>
> O 170.150.1.5/32 [110/64] via 170.150.1.5, 00:37:49, Serial0
> O 170.150.1.3/32 [110/128] via 170.150.1.5, 00:37:50, Serial0
> O 170.150.1.2/32 [110/128] via 170.150.1.5, 00:37:51, Se
>
> These are the IP address configured on the serial interfaces of R2, R3, and R
5.
>
> IS this the normal behavior of FR physical interface configuration? Any thin
g wrong with it?
This is very normal behavior when you use point-to-multipoint OSPF network
type in all the serial interfaces. P2M treats the subnet like a collection
of multiple P2P networks, thus advertise host routes as stub networks.
However, if you change the network type to non-broadcast or broadcast,
then the host routes will disappear, but you should watch out the next-hop
problem then.
> Q2. The above mentioned /32 networks are redistributed into RIP domain. The
y
> are showing up on R6 routing table. Why that? I thought that I should only
see
> /24 network redistributed into RIP domain from OSPF.
RIP is a classful routing protocol, but it treats host routes differently
from IGRP. It will accept the advertisements of host routes no matter
what. I do not remember why, but this is the way RIP works with /32
routes.
> Q3. The /28 and /30 networks are not being redistributed into RIP domain as e
xpected.
> There are two ways I know to fix the problem.
> a. Define a static route with /24 mask on R4 and redistribute static;
> b. Pass a default a default route to RIP domain by using "default information
-originate"
> under RIP configuration.
>
> Are there other way to do it?
Both will work. Or you can summarize the /28 and /30 networks into /24
subnets using area range command and then redistribute them into RIP
domain.
Hope it helps
-Ya
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