An organization is using a link state routing protocol that is not dependent on IP addressing. Which action should be taken to enable routing across area boundaries in this environment?
A.
Assign Level 1 router interfaces to different areas
B.
Assign Level 2 routers to different areas
C.
Assign Level 1 routers to different areas
D.
Assign Level 2 router interfaces to different areas
E.
Assign Level 2 router interfaceto the backbone area
F.
Assign Level 1 router interface to the backbone area AE
the questions talking about ISIS so any answer with an interface is not good. the correct answer is B which is level 2 ROUTER (not interface) to 2 different areas
From ARCH book, 4th edition:
"IS-IS Backbone is a contiguous chain of L2-capable routers (L2 or L1/L2) that hold the information for complete interarea routing. The backbone will span multiple areas with member routers in every area." AFAIK IS-IS interface configuration lets you set the circuit level, not the area assignment itself. "B" works so far, as long as these different areas have L2 contiguous routers connecting them.
I think the correct answer should be D and E.
You cannot assign a Level 1 router to different areas. This fact excludes answers A, C, and F.
Definitions:
1. "The IS-IS Backbone is a contiguous chain of L2-capable routers (L2 and L2/L2) that hold the information for complete interarea routing."
2. "Level 2 routing is routing between different areas".
3. "Level 1 router: this router knows the topology only of its own area and has Level 1 or Level1/Level 2 neighbors in this area."
4. "Level 2 router: this router may have neighbors in the same or in different areas, and it has a Level 2 link-state database with all information for interarea routing."
IN the question it's clear that we are talking about IS-IS. We have 3 types of routers in IS-IS. Level1, Level2 and Level1/2. to move from one Area to another one you need on 1 router have one interface that will be in the Area (level1) and second interface that will allow connect to other router in other area (level2). So in generally you need L1/L2 router (there is not such answer available) and to be more precise you need router with Lvl2 int connected to other router with Lvl2 int from other area. Best and I think only correct answer is D
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_isis/configuration/xe-16/irs-xe-16-book/irs-ovrvw-cf.html
B. You can't assign router interface to some level in IS-IS, it's possible only for entire router. So for communicate between areas we need configure our routers as L2 (interarea database)
My best guess would be answer D. The net address defines the area the router belongs to so you cannot assign a router to multiple area's (although I just noticed you can assign multiple net addresses to a router but unsure how that will behave) . In order to route between area's you need to connect a level-2 router to a level-2 router in a different area. There is no backbone-area in IS-IS, there is only a level-2 database that represents a backbone. So answer D... Anyone?
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