From: Chris Aguillo (ccaguillo1@hotpop.com)
Date: Tue Jul 12 2005 - 01:55:05 GMT-3
Hi ccie_06,
upon you start the OSPF process, the algorithm will check which
interface is part of an OSPF area or not.
Each NETWORK command is treated sequentially as it is written under the
ROUTER OSPF command.
Also in each every NETWORK ip_address inverse_mask command, you will
treat it as it is an ACL.
taking out from your original script:
network 0.0.0.0 255.255.255.255 area 0
>>> 0.0.0.0 255.255.255.255 means all IP-Address will match
>>> any interface that have a valid IP address and will be placed in Area0
network 1.2.3.0 0.0.0.0 area 1
>>> The IP address 1.2.3.0 is a host address as per inverse_mask
>>> The Interface that have the IP address of 1.2.3.0 is pulled out
from area 0 and placed into area 1.
network 1.2.3.4 0.0.0.0 area 2
>>> The IP address 1.2.3.4 is a host address as per inverse_mask
>>> The Interface that have the IP address of 1.2.3.4 is pulled out
from area 0 and placed into area 2
As a result, all router interfaces are in Area 0 except 1.2.3.0 and
1.2.3.4 which are in Area 1 and Area 2 respectively.
Moreover, reversing the Network statement and placing as the last
statement the command
NETWORK 0.0.0.0 255.255.255.255 AREA 0
>>> this will remove all interfaces assigned in other Areas (earlier
NETWORK command) and will bring other interfaces not yet assigned for
any Area and all be brought into AREA 0.
>>> This is in effect because the Network command is treated sequencially.
I do not see why network 1.2.3.0 0.0.0.0 will not match any interface
and no interface as a result will be in AREA 1 as per Godswill below?
>>> as long as there is a valid IP_address configured in the router as
1.2.3.0, that only interface will be placed in AREA 1.
I do not agree with the explanation of Godswill for:
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
network 0.0.0.0 255.255.255.255 area 0 -> Will match ALL remaining
interfaces not previously matched and place them into area 0.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The network command is placed as the first item in the series of Network
command, thus it will make all interface in the area 0 (whether or not
matched in other network command, take note this network is the first
one). The way I analyzed the words <<<all remaining>>> and <<<not
previously mathed>>> is probably he thinks that Network Command is not
trated sequentially.
HTH....chris
Godswill Oletu wrote:
> The interfaces will be assigned like this:
> network 1.2.3.0 0.0.0.0 area 1 -> Will not match any interface, no
> interface will be in area 1
>
> network 1.2.3.4 0.0.0.0 area 2 -> Will match only interface 1.2.3.4 and
> put it into area 2
>
> network 0.0.0.0 255.255.255.255 area 0 -> Will match ALL remaining
> interfaces not previously matched and place them into area 0.
>
> Thanks.
> Godswill Oletu
>
> ----- Original Message ----- From: "ccie_06" <ccie_06@att.net>
> To: <ccielab@groupstudy.com>
> Sent: Sunday, July 10, 2005 12:29 PM
> Subject: Ospf Network statement
>
>
>> Can any one explain following statement under ospf process ( I mean
>> which interface will participate in which area.?)
>>
>> router ospf 1
>> network 0.0.0.0 255.255.255.255 area 0
>> network 1.2.3.0 0.0.0.0 area 1
>> network 1.2.3.4 0.0.0.0 area 2
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