From: Ovais Iqbal (ovais.iqball@yahoo.com)
Date: Mon Oct 27 2008 - 02:20:00 ARST
Dear Fahad, kindly look at the following para from RFC 2328
Match the Area ID of the receiving interface. In this
case, the packet has been sent over a single hop.
Therefore, the packet's IP source address is required to
be on the same network as the receiving interface. This
can be verified by comparing the packet's IP source
address to the interface's IP address, after masking
both addresses with the interface mask. This
comparison
should not be performed on point-to-point networks. On
point-to-point networks, the interface addresses of each
end of the link are assigned independently, if they are
assigned at all.
Now as per the bolded lines, on p2p networks the comparison for same
network/subnet shouldnt be made at all, but i dont think IOS implement this
!!
--- On Sun, 10/26/08, amernas <taloust@gmail.com> wrote:
From: amernas <taloust@gmail.com>
Subject: Re: OSPF Adj in case of different subnet masks of neighbours
To: "Fahad Khan" <fahad.khan@gmail.com>
Cc: "Jason Madsen" <madsen.jason@gmail.com>, "Cisco certification"
<ccielab@groupstudy.com>
Date: Sunday, October 26, 2008, 8:46 PM
The mask is one of the parameters in the ospf hello packet. in broadcast and
NBMA network the mask should match on both sides otherwise the basic
connectivity will not work. In point-to-point network the mask does not have
to
be the same and ospf ignores this check.
*Mar 1 00:09:06.443: OSPF: Dead R 40 C 40, Hello R 10 C 10 Mask R
>> 255.0.0.0 C
>> 255.255.0.0
Fahad Khan wrote:
> hmmm.....well network type is same on both ends that is
"broadcast", i set
> it under interface mode. the only different thing is subnet mask. but i
> wonder to see why its prompting as "Mismatched hello
parameters"...
>
> On 10/27/08, Jason Madsen <madsen.jason@gmail.com> wrote:
>
>> Fahad,
>>
>> You can mix OSPF types, but NOT if one type requires a DR (broadcast,
>> non-broadcast) with a type that doesn't use a DR (p2p, p2m, and
p2m
>> non-broadcast)...it won't work. If mixing compatible types just
remember to
>> consider timers...they must match.
>>
>> Jason
>>
>> On Sun, Oct 26, 2008 at 2:24 PM, Fahad Khan
<fahad.khan@gmail.com> wrote:
>>
>>
>>> Dear All,
>>>
>>> Have a look to the scenario,
>>>
>>>
>>>
R1(s1/0-10.0.0.1/*16*)------------------(10.0.0.2/*8*-s1/0)R2<http://10.0.0..
2/*8*-s1/0%29R2>
>>>
>>> *OSPF adj forms* in case if i set the network type
"point-to-point" on
>>> both
>>> serial interfaces
>>>
>>> But if I set network type as "Broadcast", *adj is not
formed*
>>>
>>> and the "debug ip ospf adj+events+packets" looks like
(on R1);
>>>
>>> *Mar 1 00:08:58.783: OSPF: Send with youngest Key 0
>>> *Mar 1 00:08:58.783: OSPF: Send hello to 224.0.0.5 area 0 on
Serial1/0
>>> from
>>> 10.
>>> 0.0.1
>>> *Mar 1 00:09:06.431: OSPF: rcv. v:2 t:1 l:44 rid:2.2.2.2
>>> aid:0.0.0.0 chk:0 aut:2 keyid:0 seq:0x3C7EC691 from Serial1/0
>>> *Mar 1 00:09:06.435: OSPF: Rcv hello from 2.2.2.2 area 0 from
Serial1/0
>>> 10.0.0.
>>> 2
>>> *Mar 1 00:09:06.439: OSPF: Mismatched hello parameters from
10.0.0.2
>>> *Mar 1 00:09:06.443: OSPF: Dead R 40 C 40, Hello R 10 C 10 Mask
R
>>> 255.0.0.0 C
>>> 255.255.0.0
>>>
>>> Can any body shed light on the reason behind all this?
>>> Thanks in advance
>>>
>>> best regards,
>>> --
>>> Fahad Khan
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>>
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