From: Nathasha Aleyevka (naleyevka@yahoo.com)
Date: Sat Jan 17 2004 - 00:24:07 GMT-3
I want to migrate a new area into an existing one, without impacting the existing routing process, based on your explanation that is multihoming;-)
Thank you very much Marvin.
Nathasha
Marvin Greenlee <marvingreenlee@yahoo.com> wrote:
Are you wanting to do multihoming or multiarea? As
you have it configured, you will do multihoming and
the areas will be merged.
******
Multihoming vs. Multiarea
Multihoming runs both NETs under the same process,
effectively merging the areas together.
Router isis
Net 49.0001.1111.1111.1111.00
Net 49.0002.1111.1111.1111.00
Multiarea is configuring multiple IS-IS processes with
tags.
Int Eth0
router isis A3253-02
Int Eth1
router isis A3253-01
Int Ser0
router isis BB
router isis BB
net 49.2222.0000.0000.0005.00
!
router isis A3253-01
net 49.0553.0001.0000.0000.0005.00
is-type level-1
!
router isis A3253-02
net 49.0553.0002.0000.0000.0005.00
is-type level-1
Reference - Cisco - IS-IS multi-area support
http://www.cisco.com/en/US/customer/products/sw/iosswrel/ps1830/products_feature_guide09186a00800e9780.html#wp1034096
*******
Cisco Press - IS-IS Network Design Solutions
Multihoming
"...the devices begin to exchange all their originally
separate Level 1 databases, which are then flooded to
the other level 1 neighbors. This effectively merges
the two areas."
Multi-area
"Multi-area support allows a single router to
participate in up to 29 independent Level 1 areas with
one of them doubling as Level 2 if necessary...
...Redistribution between processes is not allowed;
however, external routing sources can be redistributed
into each area independently."
********
Key points are how Level 1 and 2 are affected.
Multi-area
Max 1 Level 2
Level 1 processes independent
Cannot redistribute between processes
Can redistribute external routing sources into each
area independently
Multihoming
Can have multiple Level 2
Level 1 databases merged
********
Router 1---L1---Router 2---L2---Router 3
Redistributing External Routing Sources
Router 1 in Area 47.001
Router 3 in Area 49.001
Router 2 in Areas 47.001 and 49.001 via multi-area
(two processes)
Router 2 has a loopback under ospf process 5.
You can redistribute into either ISIS process.
router isis 47
redistribute ospf 5 level-1
or
router isis 49
redistribute ospf 5
If you redistribute into process 47, the route will
appear on Router 1. If you redistribute into process
49, the route will appear on router 3. R2 will not let
you redistribute from one isis process to the other.
Sincerely,
Marvin Greenlee, CCIE #12237
Network Learning, Inc.
Senior Technical Advisor
marvin@eccie.com
--- Nathasha Aleyevka wrote:
> Hi,
>
>
>
> I tried configuring ISIS with 2 areas on the same
> router(R1), with one interface E0 in area 49.0001
> and S0/0 in area 48.0001. I have enabled the ISIS
> process on the router and assigned area and system
> ID to the router:
>
> Interface Ethernet0
> ip address 172.16.12.2 255.255.255.0
> ip router isis
> !
>
> Interface Serial0
> ip address 12.16.23.1 255.255.255.252
> ip router isis
> !
>
> router ISIS
>
> net 49.0001.0000.0001.00
> net 48.0001.0000.0001.00
>
> How does the router know which interface is
> connected to area 48 vs 49?
>
> Can I configure the E0 interface with clns net
> 47.0001.0000.0001.00 in order to assign this
> interface to a 3rd area? To connect a new area to
> the existing one via E0 would I configure this
> interface as isis circuit-type level-1-2 and assign
> the clns net XX.XXXX....XX where XX is the new area?
> Or just configure the E0 as isis circuit-type
> level-1-2 and under the router ISIS process
> configure the new area.
>
> Thank you
>
> Nathasha
>
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