CCIE R/S Written Sample Question - Part 2

If you are interested in Part 1 of this blog series - click here.

Question 2 of 105

Given the topology and configurations shown in the exhibits. Which devices will receive EIGRP Query packets if R1 loses its route information for the 10.10.10.0/24 prefix?

a) None of the devices

b) R2, R3, R4, R5, R6, R7

c) R2, R3, R6, R7

d) R2, R3, R4, R5

e) R2, R3

Exhibit 1

Exhibit 2

R2#show run
Building configuration...

Current configuration : 877 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
no aaa new-model
memory-size iomem 5
ip cef
!
no ip domain lookup
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
!
interface FastEthernet0/0
description Link to R1
ip address 10.20.20.2 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description Link to R4
ip address 10.24.24.2 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet1/0
description Link to R5
ip address 10.25.25.2 255.255.255.0
duplex auto
speed auto
!
router eigrp 100
network 10.0.0.0
auto-summary
!
ip forward-protocol nd
!
ip http server
no ip http secure-server
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
!
end

Exhibit 3

R3#show run
Building configuration...

Current configuration : 982 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
boot-start-marker
boot-end-marker
!
no aaa new-model
memory-size iomem 5
ip cef
!
no ip domain lookup
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
!
interface FastEthernet0/0
description Link to R1
ip address 10.30.30.3 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description Link to R6
ip address 10.36.36.3 255.255.255.0
ip summary-address eigrp 100 10.0.0.0 255.0.0.0 5
duplex auto
speed auto
!
interface FastEthernet1/0
description Link to R7
ip address 10.37.37.3 255.255.255.0
ip summary-address eigrp 100 10.0.0.0 255.0.0.0 5
duplex auto
speed auto
!
router eigrp 100
network 10.0.0.0
no auto-summary
!
ip forward-protocol nd
!
ip http server
no ip http secure-server
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
!
end

In order to solve this question, we must remember the various options for Query Scoping that were covered in the CCIE R/S Written Class On Demand, and in Petr's excellent blog post. Remember, summarization, multiple EIGRP ASes, EIGRP Stub, and prefix filtering are all methods of scoping queries.

In this example, we examine R2's configuration and learn that automatic summarization is left on. But this has no effect whatsoever in this scenario as all devices are numbered in the same major classful network space. On R3, we notice that manual summarization is being accomplished, but notice that will scope the queries at R6 and R7. So any devices BEYOND R6 and R7 will not receive the queries for this subnet, but those devices will indeed receive them.

In summary (no pun intended), we just need to remember here two basic concepts from the course. What are the options to scope queries? How will they impact the query behavior once implemented.

So our answer - option b - R2, R3, R4, R5, R6, and R7 all receive query packets for this network.