On the basis of the exhibit provided, assuming that EIGRP is the routing protocol, then at R5, what
would be the status of each path to 172.30.1.0/24?
A.
the path through R3 would be the successor, the path through R1 would be a feasible
successor, and the path through R4 would be neither a successor nor a feasible successor
B.
not enough information has been given to figure out what the status of each route would be
C.
the path through R3 would be the successor, and the paths through R1 and R4 would be
feasible successors
D.
the path through R1 would be the successor, the path through R3 would be a feasible
successor, and the path through R4 would be neither a successor nor feasible successor
Explanation:
I duplicated this information from within GNS3 and I received the following results
R5#show ip routeCodes: C – connected, S – static, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2
i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2
ia – IS-IS inter area, * – candidate default, U – per-user static route
o – ODR, P – periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
D 1.1.1.1 [90/25735680] via 10.1.35.1, 00:03:53, FastEthernet0/0
2.0.0.0/32 is subnetted, 1 subnets
D 2.2.2.2 [90/25733120] via 10.1.35.1, 00:03:58, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
D 4.4.4.4 [90/25743360] via 10.1.35.1, 00:03:53, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
C 5.5.5.5 is directly connected, Loopback0
172.30.0.0/24 is subnetted, 1 subnets
D 172.30.0.0 [90/25610240] via 10.1.35.1, 00:03:53, FastEthernet0/0
10.0.0.0/30 is subnetted, 6 subnets
C 10.1.15.0 is directly connected, FastEthernet1/0
D 10.1.14.0 [90/25615360] via 10.1.35.1, 00:03:55, FastEthernet0/0
D 10.1.12.0 [90/25607680] via 10.1.35.1, 00:04:03, FastEthernet0/0
D 10.1.23.0 [90/25605120] via 10.1.35.1, 00:04:03, FastEthernet0/0
C 10.1.45.0 is directly connected, FastEthernet0/1
C 10.1.35.0 is directly connected, FastEthernet0/0
R5#show ip eigrp top
IP-EIGRP Topology Table for AS(100)/ID(5.5.5.5)
Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status
P 1.1.1.1/32, 1 successors, FD is 25735680
via 10.1.35.1 (25735680/25733120), FastEthernet0/0
via 10.1.15.1 (25753600/128256), FastEthernet1/0
P 2.2.2.2/32, 1 successors, FD is 25733120
via 10.1.35.1 (25733120/25730560), FastEthernet0/0
via 10.1.15.1 (25756160/25730560), FastEthernet1/0
P 4.4.4.4/32, 1 successors, FD is 25743360
via 10.1.35.1 (25743360/25740800), FastEthernet0/0
via 10.1.45.1 (25753600/128256), FastEthernet0/1via 10.1.15.1 (25761280/25735680), FastEthernet1/0
P 5.5.5.5/32, 1 successors, FD is 128256
via Connected, Loopback0
P 10.1.15.0/30, 1 successors, FD is 25625600
via Connected, FastEthernet1/0
P 10.1.14.0/30, 1 successors, FD is 25615360
via 10.1.35.1 (25615360/25612800), FastEthernet0/0
via 10.1.15.1 (25633280/25607680), FastEthernet1/0
via 10.1.45.1 (25633280/25607680), FastEthernet0/1
P 10.1.12.0/30, 1 successors, FD is 25607680
via 10.1.35.1 (25607680/25605120), FastEthernet0/0
via 10.1.15.1 (25628160/25602560), FastEthernet1/0
P 10.1.23.0/30, 1 successors, FD is 25605120
via 10.1.35.1 (25605120/25602560), FastEthernet0/0
P 10.1.45.0/30, 1 successors, FD is 25625600
via Connected, FastEthernet0/1
P 10.1.35.0/30, 1 successors, FD is 25602560
via Connected, FastEthernet0/0
P 172.30.0.0/24, 1 successors, FD is 25610240
via 10.1.35.1 (25610240/25607680), FastEthernet0/0
via 10.1.15.1 (25628160/28160), FastEthernet1/0
Relevant portion of R5 Configuration
!
hostname R5
!
interface Loopback0
ip address 5.5.5.5 255.255.255.255
!
interface FastEthernet0/0
description ##Connection_To_R3##
bandwidth 100
ip address 10.1.35.2 255.255.255.252
delay 10
duplex auto
speed auto
!
interface FastEthernet0/1
description ##Connection_To_R4##
bandwidth 100
ip address 10.1.45.2 255.255.255.252delay 100
duplex auto
speed auto
!
interface FastEthernet1/0
description ##Connection_To_R1##
bandwidth 100
ip address 10.1.15.2 255.255.255.252
delay 100
duplex auto
speed auto
!
router eigrp 100
network 5.5.5.5 0.0.0.0
network 10.1.15.0 0.0.0.3
network 10.1.35.0 0.0.0.3
network 10.1.45.0 0.0.0.3
no auto-summary
Successor
A successor for a particular destination is a next hop router that satisfies these two conditions:
It provides the least distance to that destination
It is guaranteed not to be a part of some routing loop
The first condition can be satisfied by comparing metrics from all neighboring routers that
advertise that particular destination, increasing the metrics by the cost of the link to that respective
neighbor, and selecting the neighbor that yields the least total distance. The second condition can
be satisfied by testing a so-called Feasibility Condition for every neighbor advertising that
destination. There can be multiple successors for a destination, depending on the actual topology.
The successors for a destination are recorded in the topology table and afterwards they are used
to populate the routing table as next-hops for that destination.
Feasible Successor
A feasible successor for a particular destination is a next hop router that satisfies this condition:
It is guaranteed not to be a part of some routing loop
This condition is also verified by testing the Feasibility Condition.
Thus, every successor is also a feasible successor. However, in most references about EIGRP the
term “feasible successor” is used to denote only those routers which provide a loop-free path but
which are not successors (i.e. they do not provide the least distance). From this point of view, for a
reachable destination there is always at least one successor, however, there might not be any
feasible successors.A feasible successor provides a working route to the same destination, although with a higher
distance. At any time, a router can send a packet to a destination marked “Passive” through any of
its successors or feasible successors without alerting them in the first place, and this packet will be
delivered properly. Feasible successors are also recorded in the topology table.
The feasible successor effectively provides a backup route in the case that existing successors
die. Also, when performing unequal-cost load-balancing (balancing the network traffic in inverse
proportion to the cost of the routes), the feasible successors are used as next hops in the routing
table for the load-balanced destination.
By default, the total count of successors and feasible successors for a destination stored in the
routing table is limited to four. This limit can be changed in the range from 1 to 6. In more recent
versions of Cisco IOS (e.g.
12.4), this range is between 1 and 16.
EIGRP Composite and Vector metrics
Bandwidth
Minimum Bandwidth (in kilobits per second) along the path from router to destination network
Load
Load (number in range 1 to 255; 255 being saturated)
Delay
Total Delay (in 10s of microseconds) along the path from router to destination network
Reliability
Reliability (number in range 1 to 255; 255 being the most reliable)
MTU
Minimum path Maximum Transmission Unit (MTU) (never used in the metric calculation)
Hop Count
Number of routers a packet passes through when routing to a remote network, used to limit the
EIGRP AS.
The K Values There are five (5) K values used in the Composite metric calculation – K1 through
K5. The K values only act as multipliers or modifiers in the composite metric calculation. K1 is not
equal to Bandwidth, etc.
By default, only total delay and minimum bandwidth are considered when EIGRP is started on a
router, but an administrator can enable or disable all the K values as needed to consider the other
Vector metrics.http://en.wikipedia.org/wiki/EIGRP#Successor