topic Re: OSPF Routing Problem in Routing and SD-WAN

OSPF Routing Problem

1lumkk — Mon, 04 Mar 2019 11:28:08 GMT

My R3 acts as a frame-relay switch connecting R1. The frame-relay circuit is up. However, R1 is unable to see R6 thru ospf routing. Attached here is the config & diagram to explain. Hope some1 can help this novice. Many thanks.

Re: OSPF Routing Problem

Leo Laohoo — Sun, 08 Feb 2009 20:43:52 GMT

Where's your OSPF network statement?

Re: OSPF Routing Problem

royalblues — Sun, 08 Feb 2009 21:10:47 GMT

I am not sure i understand what you are trying to achieve

R3 is a FR switch for R1 on one side but which device on the other?. I assume it should be R6 but then the R3 and R6 are connecting via ethernet.

Your frame-relay will be up as the FR switch provides the required clock but doesnt have a FR PVC

HTH

Narayan

Re: OSPF Routing Problem

royalblues — Sun, 08 Feb 2009 21:30:12 GMT

Ok i understand your topology now.. the Frame circuit PVC is between R1 & R2

The route adv should be R6-eth-R3-eth- R2-FR-R1

With the current config you have a partioned area with Area 3 connecting to area 2 directly and not connecting via backbone area 0

Trying chnaging the fastethernet links between R1 and R3 to area 0 and it should work (or build a virtual-link)

HTH

Narayan

Re: OSPF Routing Problem

sujitkr7cisco — Sun, 08 Feb 2009 21:58:50 GMT

Dear,

Great, use virtual connnectivity between them and also you can use default route(but not neccessary).

Thanks ,

sujeet

Re: OSPF Routing Problem

1lumkk — Thu, 12 Feb 2009 17:11:49 GMT

Hi Nara,

I had tried to change R1 and R3 to area 0 but it doesn't seem to work. I guess it is something to do with my R3 connectivity to R1 which is a frame-relay. A show ip ospf interface on R3 doesn't seem to list the serial int connecting to R1 as ospf interface. Problem still unresolved.

Re: OSPF Routing Problem

royalblues — Thu, 12 Feb 2009 17:15:47 GMT

can you post the configurations of R1 an R3

Narayan

Re: OSPF Routing Problem

Giuseppe Larosa — Fri, 13 Feb 2009 16:50:39 GMT

Hello Lum,

have you used ip ospf 1 area 0 on the serial interfaces changing from ip ospf 1 area 2 ?

You may help the router to restart OSPF process on interfaces by shutting and then no shutting the interface to make it to restart.

Hope to help

Giuseppe

Re: OSPF Routing Problem

Mohamed Sobair — Fri, 13 Feb 2009 17:41:02 GMT

Hi,

The Frame-relay Switch shouldnt participate in the layer-3 routing , here (OSPF), the Functionality of FR-Switch is to provide Connectivity between DTEs at layer-2 based on their DLCIs info.

Inorder for R1 to have reachability to R6 through OSPF routing, then the following has to be applied:

1- Area Must match

2- Stub flag.

3- Hello and Dead Intervals.

Looking at your topolgy, Router 1 and router 6 has to be in the same OSPF area.

HTH

Mohamed

Re: OSPF Routing Problem

royalblues — Fri, 13 Feb 2009 18:11:46 GMT

Mohamed,

Actually i had the same doubt earlier but the topology is setup like this

The route adv should be R6-eth-R3-eth- R2-FR-R1.. so it is not necessary to have R1 and R6 in the same area.

But as said earlier and reiterated by Guiseppe, the serial connection between R2 and R3 need to be in area 0

Narayan

Re: OSPF Routing Problem

CriscoSystems — Sat, 14 Feb 2009 01:10:56 GMT

Mohammed, there is one Layer 2 connection from R2 to R1 (over frame); and a separate L2 connection from R2 to R6 (over FE & via R3).

It seems to me then that since R1 and R6 are both getting into different interfaces on R2, they wouldn't need to be in the same area, right? Wouldn't R2 simply become an ABR between Area 0 (frame interface to R1) and Area 2 (FE interface to R3)? Yes I know this still doesn't get us into Area 3 and R6 but I just want to see if I understand the concepts here.

Re: OSPF Routing Problem

CriscoSystems — Sat, 14 Feb 2009 01:23:22 GMT

But there ISN'T a FastEth link between R1 and R3; there's only a serial link; and the interface on R3 isn't even participating in OSPF.

The problem as I see it is that R3 does not have a single interface assigned to the backbone area. It's got FastEth into Area 3 and another FastEth into Area 2. Its serial interfaces are Layer 2 only. The only backbone ROUTERS are R2 and R1.

So either

a) build a virtual link from R3 area 3 to R2 area 0; or

b) Configure OSPF on R3; make Area 0 point-to-multipoint with R2 and R1 the spokes; make Area 3 point-to-point between R3 and R6.

Seriously, why is R3 only doing L2 switching for Area 0; when its Area 2 and 3 memberships prove to us it's OSPF-capable?

Re: OSPF Routing Problem

Mohamed Sobair — Sat, 14 Feb 2009 01:46:46 GMT

What FE?? the red link should represent a serial interface connectivity, while what was written is FE.

All the topology along with the config needs to be corrected.

Mohamed

Re: OSPF Routing Problem

CriscoSystems — Sat, 14 Feb 2009 01:52:47 GMT

The FE link between R2 and R3 (which constitutes Area 2) and the wholly different FE link between R3 and R6 (which constitutes Area 3).

You posted that R1 and R6 need to be in the same area; but this doesn't seem necessary since they aren't on the same Layer 2 link. They come into different interfaces on R2. (R1 comes into R2 on R2's S1/0; R6 would only come in on R2's F0/0.)

Re: OSPF Routing Problem

Mohamed Sobair — Sat, 14 Feb 2009 02:07:21 GMT

Ok, I posted that cause I presumed the original poster has made a mistake. Have you checked the Frame-relay Switch config? if so, do you think its valid config? Have you looked at the topology?

HTH

Mohamed

Re: OSPF Routing Problem

CriscoSystems — Sat, 14 Feb 2009 02:09:10 GMT

The diagram is a little confusing. Red is the serial link and there is a partially obscured black line representing FE between R2 and R3.

I think we might benefit from seeing the running config on R2.

Re: OSPF Routing Problem

Mohamed Sobair — Sat, 14 Feb 2009 06:19:55 GMT

NO, Its not confusing..

Its very clear, He told verbally that R3 acts as frame-relay Switch, besides relative config are also wrong.

Mohamed

Re: OSPF Routing Problem

Giuseppe Larosa — Sat, 14 Feb 2009 12:36:50 GMT

Hello Stuey,

yes it is the FE link between R3 and R2 that needs to be part of area 0; otherwise area 3 has no connection to backbone area.

The correct note is that of Narayan.

A router can be a FR switch on some interfaces and can take part to OSPF routing on other interfaces so the config appears correct.

The only problem is that area 3 is not attached to area 0.

I agree the diagram is a little misleading.

Hope to help

Giuseppe

p.s. what about your BSCI exam ? I hope you did well