From: Thounda Craig, Jr. (tcraig@xxxxxxxxxxxxxxxx)
Date: Sat Dec 30 2000 - 09:07:21 GMT-3
This command sets the ranges of network addresses that define an OSPF area
and, optionally, the type of route
propagation. If you set two ABRs with the same range, adjacent links
(routers) will become confused <by seeing
advertisements from routers A & B with equal metrics> - hence potential
routing loop depending on destinations.
Note: This is true, if you simply used the same range (prefix) WITHOUT any
additional configuration.
Now, you could do this, by altering the metric on one of the routers (for
example, with Mission Critical Sites {MCS}, you
have a primary & secondary. By increasing the cost on the secondary, it
would then act as a "true" backup to the
primary router - that is advertising the same prefix, but now w/a higher
cost, allowing the primary to be the chosen route on return); This process
can get deeper, if the metrics get manipulated on the other end that is
receiving the advertisement, but lets assume they do not.
Theoretical answer to your original question :
Route summarization is the consolidation of advertised addresses. This
feature causes a single summary route to be advertised to other areas by an
ABR. In OSPF, an ABR will advertise networks in one area into another area.
If the network numbers in an area are assigned in a way such that they are
contiguous, you can configure the ABR to advertise a summary route that
covers all the individual networks within the area that fall into the
specified range.
Command syntax:
area area-id range 192.168.0.0 0.0.63.255 [advertise | not-advertise]
Curtis, correct me if I'm wrong.
later,
Thounda
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
fwells12
Sent: Saturday, December 30, 2000 12:22 AM
To: ccielab@groupstudy.com
Subject: Re: OSPF network statement
Thanks Curtis. Elaborate on this statement please...You do not want to use
an area range
statement in both routers.
----- Original Message -----
From: Curtis Lindsay <clindsay_98@yahoo.com>
To: fwells12 <fwells12@hotmail.com>; <ccielab@groupstudy.com>
Sent: Friday, December 29, 2000 5:51 PM
Subject: Re: OSPF network statement
> Hi,
>
> One thing you must take into consideration with the
> network command in ospf is that it acts as an access
> list to determine what links or interfaces (ie network
> address) to match and include in the ospf process for
> advertisement. It has nothing to do with conserving
> address space. You can put the same network statement
> in different routers and it will advertise the links
> that match the network statement. For example:
>
> router 1
>
> interface Loopback0
> ip address 192.168.20.2 255.255.248.0
> !
> interface Loopback1
> ip address 192.168.28.2 255.255.248.0
> !
> interface Loopback2
> ip address 192.168.36.2 255.255.248.0
> !
> interface Loopback3
> ip address 192.168.44.2 255.255.248.0=20
> !
> router ospf 100
> network 192.168.0.0 0.0.63.255 area 0.0.0.0
>
>
> router 2
> interface Loopback0
> ip address 192.168.25.2 255.255.248.0
> !
> interface Loopback1
> ip address 192.168.29.2 255.255.248.0
> !
> interface Loopback2
> ip address 192.168.37.2 255.255.248.0
> !
> interface Loopback3
> ip address 192.168.45.2 255.255.248.0
> !
> router ospf 100
> net 192.168.0.0 0.0.63.255 area 0.0.0.0
> !
> Now granted the /32 bit host address will be
> advertised. You do not want to use an area range
> statement in both routers.
>
> Curtis
> --- fwells12 <fwells12@hotmail.com> wrote:
> > I have the following IP addresses configured as
> > loopback interfaces on =
> > an OSPF router. What is the correct command to
> > insert these networks =
> > into the OSPF process in the most efficient manner?
> > By that, I mean =
> > conserving the maximum amount of IP addresses.
> >
> > interface Loopback0
> > ip address 192.168.20.2 255.255.248.0
> > !
> > interface Loopback1
> > ip address 192.168.28.2 255.255.248.0
> > !
> > interface Loopback2
> > ip address 192.168.36.2 255.255.248.0
> > !
> > interface Loopback3
> > ip address 192.168.44.2 255.255.248.0=20
> >
> > Cheers.
> >
> >
> >
> >
> >
> >
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