Home » Cisco » 300-320 » Which two elements comprise the backbone area while designing a new network utilizing IS-IS as the interior gateway protocol (choose two):
Which two elements comprise the backbone area while designing a new network utilizing IS-IS as the interior gateway protocol (choose two):
A. contiguous chain of Level 2 capable routers
B. contiguous chain of Level1/Level 2 capable routers
C. set of Level 2 configured interfaces
D. contiguous Level 1 capable routers
E. set of Level 1 configured interfaces
Correct Answer: AB
Explanation/Reference:
Explanation/Reference:
https://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a3e6f.shtml
"Backbone
IS-IS does not have a backbone area like the OSPF area 0. The IS-IS backbone is a contiguous collection of Level 2-capable routers, each of which can be in a different area"
http://www.ciscopress.com/articles/article.asp?p=26850&seqNum=3
"In most designs with routing hierarchy, the Level 2 routers are als o Level 1 routers by virtue of their identification with a certain area. Therefore, in IS-IS, a router can function as Level 1-only or Level 2-only and possibly as both Level 1 and Level 2 (Level 1-2). Level 1-2 routers act as border routers to their respective areas, providing connectivityto other areas.
The Level 2 backbone is es s entially a virtual IS-IS area consisting of routers engaged in Level 2 routing"
