Correct Answer: B
Explanation/Reference:
Explanation:
Auto-Summarization of External Routes
EIGRP will not auto-summarize external routes unless there is a component of the same major network that is an internal route. To illustrate, let us look at Figure 15.
Router Three is injecting external routes to 192.1.2.0/26 and 192.1.2.64/26 into EIGRP using the redistribute connected command, as shown in the configurations below.
Router Three
interface Ethernet0
ip address 192.1.2.1 255.255.255.192
!
interface Ethernet1
ip address 192.1.2.65 255.255.255.192
!
interface Ethernet2
ip address 10.1.2.1 255.255.255.0
!
router eigrp 2000
redistribute connected
network 10.0.0.0
default-metric 10000 1 255 1 1500
With this configuration on Router Three, the routing table on Router One shows:
one# show ip route
10.0.0.0/8 is subnetted, 2 subnets
D 10.1.2.0 [90/11023872] via 10.1.50.2, 00:02:03, Serial0 C 10.1.50.0 is directly connected, Serial0
192.1.2.0/26 is subnetted, 1 subnets
D EX 192.1.2.0 [170/11049472] via 10.1.50.2, 00:00:53, Serial0 D EX 192.1.2.64 [170/11049472] via
1
1
0.1.50.2, 00:00:53, Serial0 Although auto-summary normally causes Router Three to summarize the
92.1.2.0/26 and 192.1.2.64/26 routes into one major net destination (192.1.2.0/24), it does not do this because both routes are external. However, if you reconfigure the link between Routers Two and Three to
92.1.2.128/26, and add network statements for this network on Routers Two and Three, the 192.1.2.0/24
1
auto-summary is then generated on Router Two.
Router Three
interface Ethernet0
ip address 192.1.2.1 255.255.255.192
!
interface Ethernet1
ip address 192.1.2.65 255.255.255.192
!
interface Serial0
ip address 192.1.2.130 255.255.255.192
!
router eigrp 2000
network 192.1.2.0
Now Router Two generates the summary for 192.1.2.0/24:
two# show ip route
D 192.1.2.0/24 is a summary, 00:06:48, Null0
And Router One shows only the summary routE.
one# show ip route
10.0.0.0/8 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0
D 192.1.2.0/24 [90/11023872] via 10.1.50.2, 00:00:36, Serial0
Reference. http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing- protocol- eigrp/16406-eigrp-toc.html