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352-001 · Question #20

Refer to the exhibit. In this network, all routers are configured to run EIGRP on all interfaces. All interface bandwidths are set to 1000, and the delays are configured as shown. In the topology tabl

The correct answer is C. Router D is not advertising 10.1.1.0/24 to Router C due to split horizon.. EIGRP split horizon prevents Router D from advertising 10.1.1.0/24 back out the same interface through which it learned the route toward Router C, resulting in only one path appearing in Router C's topology table.

Layer 3 Control Plane

Question

Refer to the exhibit. In this network, all routers are configured to run EIGRP on all interfaces. All interface bandwidths are set to 1000, and the delays are configured as shown. In the topology table at Router C, you see only one path towards 10.1.1.0/24. What is the reason that Router C only has one path in its topology table?

Options

  • ARouter D is not advertising 10.1.1.0/24 to Router C because Router C is its feasible successor.
  • BRouter B is not advertising 10.1.1.0/24 to Router C because Router C is its feasible successor.
  • CRouter D is not advertising 10.1.1.0/24 to Router C due to split horizon.
  • DRouter B is not advertising 10.1.1.0/24 to Router C due to split horizon.

How the community answered

(24 responses)
  • A
    4% (1)
  • B
    4% (1)
  • C
    83% (20)
  • D
    8% (2)

Why each option

EIGRP split horizon prevents Router D from advertising 10.1.1.0/24 back out the same interface through which it learned the route toward Router C, resulting in only one path appearing in Router C's topology table.

ARouter D is not advertising 10.1.1.0/24 to Router C because Router C is its feasible successor.

Feasible successor status at Router C does not cause Router D to suppress its advertisement - EIGRP routers advertise all known prefixes to neighbors regardless of the neighbor's role in the remote topology table.

BRouter B is not advertising 10.1.1.0/24 to Router C because Router C is its feasible successor.

A neighbor being a feasible successor in Router B's topology table has no bearing on whether Router B sends updates for that prefix, because feasible successor designation affects only local path selection and not update propagation.

CRouter D is not advertising 10.1.1.0/24 to Router C due to split horizon.Correct

EIGRP split horizon is a loop-prevention rule that prohibits a router from advertising a prefix back out the interface through which it originally received that prefix. If Router D learned about 10.1.1.0/24 via the link connecting it to Router C, split horizon stops Router D from re-advertising that prefix back to Router C, so Router C sees only the single path it already knows through another neighbor.

DRouter B is not advertising 10.1.1.0/24 to Router C due to split horizon.

Split horizon on Router B would prevent Router B from re-advertising 10.1.1.0/24 back out the interface toward its source, but the topology's delay values indicate Router D - not Router B - is the router suppressing the advertisement due to split horizon.

Concept tested: EIGRP split horizon suppressing route advertisements

Source: https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13669-1.html

Topics

#EIGRP#split horizon#topology table#feasible successor

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