Refer to the exhibit.
From R1, a network administrator is able to ping the serial interface of R2 but, unable to ping any
of the subnets attached to RouterB. Based on the partial outputs in the exhibit, what could be the
problem?
A.
EIGRP does not support VLSM.
B.
The EIGRP network statements are incorrectly configured.
C.
The IP addressing on the serial interface of RouterA is incorrect.
D.
The routing protocol has summarized on the classful boundary.
E.
EIGRP has been configured with an invalid autonomous system number.
Eigrp Auto summrization summarizes to a classful boundary when passes through DIFFERENT major Network Boundaries.
By default, EIGRP has auto summary feature enabled. Because of this, routes are summarized to classful address at network boundaries in the routing updates.
The auto summary feature can cause problems with discontiguous networks. Auto-summary creates problems if there is a discontiguous classful network. Autosummary is enabled by default while using RIP v1, RIP v2 and EIGRP.
How a route to Null0 works in EIGRP? A null interface is basically a trash, whatever you send to a null interface is the same as dropping the traffic. EIGRP always creates a route to the Null0 interface when it summarizes a group of routes. So it’s basically a Loop Prevention mechansim. Traffic destined for any specific route that’s part of summary but doesn’t exist in one of case where it will silently drop the traffic and preventing traffic from looping around.
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EIGRP supports VLSM as all IP routing updates do.
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The Autonomous System Number (ASN) value 0 is reserved, and the largest ASN value 65,535, is also reserved. The values, from 1 to 64,511, are available for use in Internet routing, and the values 64,512 to 65,534 is designated for private use.
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Enter EIGRP configuration by entering router eigrp 1. The “1” is the autonomous system number. This number must match the configured autonomous system number currently configured on R1.
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From the output of “show ip route” command on RouterB, we learn that RouterB does not learn any networks in RouterA. Also the “172.16.0.0/26 is a summary, 00:00:03, Null0” line tells us this netwok is summarized.
Note: EIGRP performs auto-summarization each time it crosses a border between two major networks. For example, RouterA has networks of 172.16.x.x. It will perform auto-summarization when sending over network 10.1.1.0/30, which is in different major network (172.16.0.0/16 and 10.0.0.0/8 are called major networks in this case).
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Only serial 0/0 is connected, but 10.0.0.0 is on the summary Null0, so it is auto-summarization
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The sub interfaces are summerized subnets, so can only reach the serial interface but not the subinterfaces
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