problem with OSPF over NBMA

mirror51

The CBT Nuggets of Cicso Route exam says that

In the Video i need to configure the OSPF in Network without using OSPF network statement in hub and spoke configuration


I am using framerelay by this command


[HTML]int s0/1.1 multipoint
ip add 10.35.6.3 255.255.255.0
frame-relay map ip 10.35.6.5 305 br
frame-relay map ip 10.35.6.6 306 br


int s0/0
en fr
ip add 10.35.6.5 255.255.255.0
frame-relay map ip 10.35.6.3 503 br
frame-relay map ip 10.35.6.6 503 br


int s0/0
en fr
ip add 10.35.6.6 255.255.255.0
frame-relay map ip 10.35.6.3 603 br
frame-relay map ip 10.35.6.5 603 br[/HTML]


Then the ospf

router ospf 1
router-id 8.8.8.8
log-adjacency-changes
network 8.8.8.8 0.0.0.0 area 356
network 10.35.6.0 0.0.0.255 area 356

NOW when i type

show ip ospf int

Then i see the network type as

 Network Type NON_BROADCAST,

But in the video he sees as

Network Type POINT-TO-POINT

He has not use any network statamenet but his network type is point-to-point by default but mine is showing non -broad cast

where i am wrong

Forsaken_GA

Was he using point-to-point subints?

ehnde

I don't think you're wrong. NBMA is by definition non broadcast. Maybe you just jumped ahead of Jeremy in the video?

Forsaken_GA

ehnde wrote: »

I don't think you're wrong. NBMA is by definition non broadcast. Maybe you just jumped ahead of Jeremy in the video?

Well, if Jeremy is using point to point subints, those default to point to point network type (which kind of makes sense)

gregorio323

The interface defaults to NON_BROADCAST
you can either create sub interfaces and make them point-to-point
or you can use the command under the interface

R1(config-if)#ip ospf network point-to-point

Forsaken_GA

gregorio323 wrote: »

The interface defaults to NON_BROADCAST
you can either create sub interfaces and make them point-to-point
or you can use the command under the interface

R1(config-if)#ip ospf network point-to-point

The raw serial interface defaults to non broadcast

Process ID 1, Router ID 10.0.0.1, Network Type NON_BROADCAST, Cost: 64

However, a point to point sub interface does not default to NON_BROADCAST. LIke so:

R1(config)#int s0/0.1 point-to-point
R1(config-subif)#int s0/0
R1(config-if)#no ip address
R1(config-if)#int s0/0.1 poi
R1(config-subif)#ip address 10.0.0.1 255.255.255.0
R1(config-subif)#frame-relay interface-dlci 102
R1#sh ip ospf int
Serial0/0.1 is up, line protocol is up
Internet Address 10.0.0.1/24, Area 0
Process ID 1, Router ID 10.0.0.1, Network Type POINT_TO_POINT, Cost: 64


P2P subints default to P2P network types, which is why it's important for the OP to find out whether he made a mistake in what he saw in the nugget in thinking it was a multipoint interface, instead of a p2p subint.

These are the finer details of OSPF that need to be learned.

gregorio323

Forsaken_GA wrote: »

The raw serial interface defaults to non broadcast

Process ID 1, Router ID 10.0.0.1, Network Type NON_BROADCAST, Cost: 64

However, a point to point sub interface does not default to NON_BROADCAST. LIke so:

R1(config)#int s0/0.1 point-to-point
R1(config-subif)#int s0/0
R1(config-if)#no ip address
R1(config-if)#int s0/0.1 poi
R1(config-subif)#ip address 10.0.0.1 255.255.255.0
R1(config-subif)#frame-relay interface-dlci 102
R1#sh ip ospf int
Serial0/0.1 is up, line protocol is up
Internet Address 10.0.0.1/24, Area 0
Process ID 1, Router ID 10.0.0.1, Network Type POINT_TO_POINT, Cost: 64


P2P subints default to P2P network types, which is why it's important for the OP to find out whether he made a mistake in what he saw in the nugget in thinking it was a multipoint interface, instead of a p2p subint.

These are the finer details of OSPF that need to be learned.

lol... that's exactly what i said that the interface defaults to NON_BROADCAST. Okay aside from that. I've watch those videos many times and i think Jeremy pre-configure the network type. I remember him mentioning it during my studies for the ROUTE exam.

Forsaken_GA

gregorio323 wrote: »

lol... that's exactly what i said that the interface defaults to NON_BROADCAST. .

The physical interface does.

subinterfaces are still full fledged interfaces as far as the router is concerned, and different types default to different values for ospf network types. You have to make the distinction, because OSPF certainly does.

It's a subtle but important difference, especially to someone who's trying to find the gap in their understanding.

gregorio323

Forsaken_GA wrote: »

The physical interface does.

subinterfaces are still full fledged interfaces as far as the router is concerned, and different types default to different values for ospf network types. You have to make the distinction, because OSPF certainly does.

It's a subtle but important difference, especially to someone who's trying to find the gap in their understanding.

lol okay okay... your right i should make distinctions between the interfaces. It would greatly help someone who is learning the material agreed.

mirror51

I am not using subinterfaces, I mean i am using only one subinterface but that is point to mulipoint on the hub

IN the lab question states that i can use

ip ospf network point to multipoint

on hub but spokes should remain to default state.

IN the video when do sh ip int breief on hub , i have checked , he was not using multiple subinterface only one subinterface so it means on hub there is only one way to configure framerelay and that is point to multipoint

Now on spokes , in video , he is not using any network statement because it was the requirement of lab , so we can't say that he used it. but it was coming as point to point

The other thing is if we leave it to non broadcast then we have to manually define the neighbor.


I am including the lab as image here



Uploaded with ImageShack.us


Now there are two types as per vieo

1)Point to multipoint
2)point to multipoint , Non broad cast

Mine case is the 2nd one which comes in area 0 of given lab but how can i achieve the case 1 that is areaa 356 as per given lab

Forsaken_GA

Well, the way that it's worded, only the ip ospf network command is off limits. it doesn't say you have to use the main interface, so you can do the configuration by putting the IP configuration on p2p subints

The trick is in knowing what interfaces default to what network mode.

mirror51

Forsaken_GA

Can you give me what statements u will use for area 356 (just FR) , if u have to do it. I am little bit confused

Forsaken_GA

mirror51 wrote: »

Forsaken_GA

Can you give me what statements u will use for area 356 (just FR) , if u have to do it. I am little bit confused

Well, I'm not going to give you a detailed answer, you won't learn anything that way

You can mix point to point links and point to multipoint links without any harm. The general gist of it is that on the non-hub routers, you configure the main interface for frame-relay encap and bring them up. Then you create a point to point subint off the main interfaces, and then give them the IP and manually define the dlci.

That will put them as ospf network type point to point without using the ip ospf network command.

The key to it is that it's saying use the default network type, and you're not allowed to use the ip ospf network command. So you have to know what interfaces default to what ospf network types (and you have to understand that subinterfaces *are* interfaces. The word interface does not automatically equal physical interface).

This is actually a pretty difficult subject, because OSPF over frame relay has so many variables. I personally think Cisco wastes waaay too much time on it these days, as frame relay links are becoming rare indeed, but you do need to understand it to pass the exams.

mirror51

ok thanks i got it working now , i didn't knew before that i can mix point-to-point and point-to-multipoint links.

SO it means there is only one way to get default ospf as point to point and that is only possible if interface is point to point.

Am i right

chamjiee

i m also trying to recreate that topology and i am having hard time recreating it same ..
had the video shown how the sub-interfaces on routers (not on the router configured as frame relay switch..) were configured for the frame relay..


i am confused by the type of the sub interface and the network type of ospf .. are they different ? how are they related ?
does ospf choses its network type automatically according to the sub interface typ ?

gregorio323 wrote: »

The interface defaults to NON_BROADCAST
you can either create sub interfaces and make them point-to-point
or you can use the command under the interface

R1(config-if)#ip ospf network point-to-point

what is the difference between

if i go to
int s1/0
no ip
enca fr
exit
int s1/0.1 point

so is there any difference between these two ?

xXErebuS

chamjiee wrote: »

i m also trying to recreate that topology and i am having hard time recreating it same ..
had the video shown how the sub-interfaces on routers (not on the router configured as frame relay switch..) were configured for the frame relay..


i am confused by the type of the sub interface and the network type of ospf .. are they different ? how are they related ?
does ospf choses its network type automatically according to the sub interface typ ?



what is the difference between

if i go to
int s1/0
no ip
enca fr
exit
int s1/0.1 point

so is there any difference between these two ?

yes; you are saying the interface s1/0 is frame relay and to treat the sub interface .1 as a P2P... so you could do S1/0.2 multipoint so S1/0.1 is P2P OSPF, S1/0.2 is NON_BROADCAST and S1/0 is NON_BROADCAST.

Think of it like this (not exactly); what Forsaken is trying to say is that the router treats the sub interfaces as if they were not sub interfaces; so it would be like saying s1/0 frame relay (default it MP); s1/1 P2P; S1/1 Frame relay MP.

Serial1/0.2 is up, line protocol is down
Internet Address 10.100.100.1/30, Area 0
Process ID 1, Router ID 10.10.10.10, Network Type NON_BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DOWN, Priority 1
No designated router on this network
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Serial1/0.1 is up, line protocol is down
Internet Address 192.168.1.1/30, Area 0
Process ID 1, Router ID 10.10.10.10, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State DOWN,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Serial1/0 is up, line protocol is down
Internet Address 10.1.1.1/30, Area 0
Process ID 1, Router ID 10.10.10.10, Network Type NON_BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DOWN, Priority 1
No designated router on this network
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120



All this and the broadcast command is added to the frame relay statements =D lol.