From: Scott Morris (swm@emanon.com)
Date: Mon Dec 25 2006 - 06:33:36 ART
There are different parts of the RFC that aren't necessarily logically
connected that answer that for ya...
In order to form a peering relationship, you need to match on:
Area ID
Timers
MTU Size
Stub Flag
Netmask (except point-to-point or virtual-links)
In order to exchange database information/routes properly, you need to agree
on some other things as well... Namely, who's in charge. With a
non-broadcast there must be a DR who is in charge. With p2mp, everyone can
send information. While this doesn't affect the peering relationship (that
would be logical) it does affect how routes do or do not show up as you are
seeing!
Anytime you have a mismatch like this, you need to be able to determine ALL
of the requirements of each network type and react accordingly. But the
peering exchange and the database exchange are two distinctly different
parts of the RFC describing OSPF operations.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
IPExpert VP - Curriculum Development
IPExpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Night War
Sent: Monday, December 25, 2006 4:07 AM
To: Cisco certification
Subject: Re: OSPF NBMA point-to-multipoint Question !!
Hello Group,
I understand that p2m and non_broadcast are not compatible but why do they
form neighbor relationship and also show that they have exchanged database
and are in FULL state. That is what I'm not able to understand. If the sh ip
ospf neighbor command says that adjacencies have formed and the routers are
in 2-WAY state then I can have a clue that something is wrong
R1 OSPF Network type : point-to-multipoint
R2 OSPF Network type : Non_Broadcast
If I'm having such a situation in my exam and if I forget to look at the
network types on the routers in the NBMA network I would be really confused.
I tried to debug ospf and I've no error messages or any problem while
forming my neighbor relationship. Do we have any specific debug commands to
know whether the network types are mismatch.
I've also copied show ip ospf database output from both the routers when
they are not exchanging routes but still neighbors and Full state.
R1#sh ip ospf database
OSPF Router with ID (150.1.1.1) (Process ID 100)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
150.1.1.1 150.1.1.1 48 0x80000002 0x006573 2
150.1.2.2 150.1.2.2 53 0x80000002 0x00413D 1
Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
150.1.1.0 150.1.1.1 49 0x80000001 0x007693
150.1.2.0 150.1.2.2 14 0x80000001 0x005EA8
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
150.1.1.1 150.1.1.1 54 0x80000001 0x00065F 1
Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
155.1.0.1 150.1.1.1 49 0x80000001 0x002CD9
R1#
R2(config)#do sh ip ospf database
OSPF Router with ID (150.1.2.2) (Process ID 100)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
150.1.1.1 150.1.1.1 229 0x80000002 0x006573 2
150.1.2.2 150.1.2.2 232 0x80000002 0x00413D 1
Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
150.1.1.0 150.1.1.1 230 0x80000001 0x007693
150.1.2.0 150.1.2.2 193 0x80000001 0x005EA8
Router Link States (Area 2)
Link ID ADV Router Age Seq# Checksum Link count
150.1.2.2 150.1.2.2 198 0x80000002 0x00EA74 1
R2(config)#
Hello ian,
I'm fine ... How are you ? I tried to reboot the routers with the same
configs I've mentioned but the same result unable to exchange routes.
I've one more question.
Referring to the same topology when
R1 OSPF Network type: point-to-multipoint
R2 OSPF Network type: point-to-point
I see that a host a route is added to R2 for the R1 serial 1/0 interface IP
Address. For eg:
O 155.1.0.1/32 [110/64] via 155.1.0.1, 00:00:15, Serial1/0
This happens most of the time if the OSPF network-type is
Point-to-Multipoint. Do we have any command to filter or not advertise to
the neighbor routers that are on the end of point-to-multipoint interfaces.
I think host route is not at all necessary as without knowing how to reach
to 155.1.0.1 I would not form OSPF neighbor relationship at the first place.
I think we have no peer neighbor-route command to disable host route in ppp
point-to-point links do we have any commands or option to disable the host
route in the frame-relay networks.
Thanks for you reply and spending your valuable time on this stupid
configuration.
Can any one give me some good titles to learn more about Advanced OSPF
routing and designing the same.
Regards
Fahad
On 12/25/06, Night War <nightwar@gmail.com> wrote:
>
> Hello Group !!
>
> Happy holidays to all members in GS !! Happy Christmas and advance New
> Year wishes to all !!
>
> I've a simple configuration shown in the topology below :
>
> loopback0 s1/0 s1/0
loopback 0
> 150.1.1.1------------------- R1 -------------()------------ R2
> ---------------------150.1.2.2
> area 1 .1 155.1.0.0 .2 area 2
>
> area 0
> (hub) (spoke)
>
>
> I'm having a problem and I would be glad if someone could explain to
> me the cause of the problem and why this problem is happening at the
> first place.
>
> I've configured and implemented OSPF based on the configuration below
> for
> R1 and R2:
>
> R1 OSPF Config and Serial 1/0 config:
>
> router ospf 100
> router-id 150.1.1.1
> network 150.1.0.0 0.0.255.255 area 1
> network 155.1.0.1 0.0.0.0 area 0
>
> interface Serial1/0
> ip address 155.1.0.1 255.255.255.0
> encapsulation frame-relay
> ip ospf network point-to-multipoint
> ip ospf hello-interval 10
> ip ospf priority 255
> frame-relay map ip 155.1.0.2 102 broadcast no frame-relay
> inverse-arp end
>
>
> R2 OSPF and Serial1/0 config:
>
> router ospf 100
> router-id 150.1.2.2
> network 150.1.0.0 0.0.255.255 area 2
> network 155.1.0.2 0.0.0.0 area 0
>
> interface Serial1/0
> ip address 155.1.0.2 255.255.255.0
> encapsulation frame-relay
> ip ospf hello-interval 10
> ip ospf priority 0
> frame-relay map ip 155.1.0.1 301 broadcast no frame-relay
> inverse-arp end
>
>
> I've purposely not give any network type on the interface of Serial
> 1/0 of router 2 (R2) the spoke. I've given the network type of
> point-to-multipoint in the Hub router of the frame-relay cloud as I
> might add more routers to the frame-relay cloud.
>
> The hello-interval and dead-interval of both R1 and R2 are the same on
> both routers namely 10 secs and 30 secs respectively.
>
> On using the configuration mentioned above for R2 and R1 I'm able to
> form adjacency and both R1 and R2 have established neighbor
> relationship. The sh ip ospf neighbor command on both the routers are
below:
>
> R1#sh ip ospf neighbor
>
> Neighbor ID Pri State Dead Time Address
> Interface
> 150.1.2.2 0 FULL/ - 00:00:34 155.1.0.2
> Serial1/0
>
>
> R2#sh ip ospf neighbor
>
> Neighbor ID Pri State Dead Time Address
> Interface
> 150.1.1.1 255 FULL/DR 00:00:35 155.1.0.1
> Serial1/0
>
>
>
> Now having said all that I've done and showing you my outputs I'm
> having the following problem. Both the routers R1 and R2 are not able
> to learn each others loopback interface which they are advertising into
the ospf domain.
> R1 is advertising 150.1.1.1 as area 1 and R2 is advertising 150.1.2.2
> as area 2. Both the routers R1 and R2 are ABR's as they have atleast
> one interface in area 0.
>
> Both the routers are not learning any routes from their neighbor even
> if I add another loopback network into area 0.
>
> the solution to the above problem is to add "ip ospf network
> point-to-point" on serial 1/0 of the spoke router R2. everything goes
> well after applying this command. both routers are learning all the
> routes. I would like to know the reason why these routers don't learn
> the routes prior to applying the "ip ospf network point-to-point" on
> serial 1/0 of R2. What is the logic for such a behavior ?
>
> Thanks
> Fahad.
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