From: Godswill Oletu (oletu@inbox.lv)
Date: Tue Jul 12 2005 - 11:22:58 GMT-3
Chris,
My conclusion was drawn from the fact that the IOS will re-order all network
statements from most specific to least specific, inrespective of how you
typed them in, the statement....
#network 0.0.0.0 255.255.255.255 area 0
Will sink to the very bottom and will be the last network statement in the
list. A 'show run' will confirm that. So, interpreting the network
statements from top to bottom, it will be safe to say that, the next least
specific network statement will only match interfaces that had not been
otherwise matched by most specific statements above it.
I am using IOS ver 12.2, all my network statements are revised from most
specific to least specific.
Agree, 1.2.3.0 will be placed into area 1, my thought process was overcomed,
by the fact that, '1.2.3.0' seems to be an odd ip address to be given to an
interface, I forgot to override that with the fact that, in the cisco world,
everything is possible.
Thanks.
---- Godswill Oletu----- Original Message ----- From: "Chris Aguillo" <ccaguillo1@hotpop.com> To: "Godswill Oletu" <oletu@inbox.lv>; "ccie_06" <ccie_06@att.net>; <ccielab@groupstudy.com> Sent: Tuesday, July 12, 2005 12:55 AM Subject: OSPF Network Statement
> 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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