From: marvin greenlee (marvin@ccbootcamp.com)
Date: Thu Mar 10 2005 - 14:30:19 GMT-3
The system ID uniquely identifies the router in the topology.
***********
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_fea
ture_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
**********
Marvin Greenlee, CCIE#12237, CCSI# 30483
Network Learning Inc
marvin@ccbootcamp.com
www.ccbootcamp.com (Cisco Training)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Thursday, March 10, 2005 9:17 AM
To: Group Study
Subject: IS-IS multi-area [bcc][faked-from][bayes]
Importance: Low
Hi guys,
I understand how to configure multiple areas by using tags like this:
!
router isis TEST-1
net 49.0001.0000.0000.0005.00
is-type level-1
!
router isis TEST-2
net 49.0002.0000.0000.0005.00
router isis TEST-3
net 49.0003.0000.0000.0005.00
But, what I can't figure out, is how to recognize a requirement for multiple
areas. How could tell that something
like the above is needed instead of something like this:
Router isis
net 49.0001.0000.0000.0001.00
net 49.0002.0000.0000.0001.00
net 49.0003.0000.0000.0001.00
BTW, why does the system ID portion of all areas have to be the same when
the area ID is different?
TIA, Tim
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