EIGRP question

PStefanov

Hi guys,

I am trying to lab a scenario in which I have mutual redistribution between OSPF and EIGRP.

R1 is connected to R2 which is connected to R4. R1 is also connected to R3 which is connected to R4. R1, R2 and R3 are running OSPF in area 0, and R2, R3 and R4 are running EIGRP. I am doing mutual redistribution between OSPF and EIGRP on R2 and R3. R3 is advertising worse metric. What I am trying to do is make R3 forward packets to the network between R1 and R2 through R4 (taking a worse path). However, I cannot do it yet. I noticed something strange (for me) at R3:

R3#sh ip eigrp top
IP-EIGRP Topology Table for AS(100)/ID(34.0.0.3)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 12.0.0.0/8, 1 successors, FD is 102656000
via Redistributed (102656000/0)
via 34.0.0.4 (2611456/2585856), FastEthernet0/0
P 13.0.0.0/8, 1 successors, FD is 10272768
via Redistributed (102656000/0)
via 34.0.0.4 (2611456/2585856), FastEthernet0/0
P 24.0.0.0/8, 1 successors, FD is 307200
via 34.0.0.4 (307200/281600), FastEthernet0/0
P 34.0.0.0/8, 1 successors, FD is 281600
via Connected, FastEthernet0/0
R3#

The feasible distance to 12.0.0.0 (the network between R1 and R2) is 102656000, not 2611456. I cannot figure out why this happens. Is there some rule or preference of locally redistributed routes versus routes learned from neighbors?

Any ideas would be very much appeciated! Thank you

Turgon

You are doing mutual distribution at two points. What metrics are you using for your redistribution? Can you post up the configs for R3 and R2?

PStefanov

The topology table below looks a bit different because I had to change some metrics, the AD of EIGRP routes and some other stuff but in R3's topology table the bigger AD is still preferred.


R2:

interface FastEthernet0/0
ip address 12.0.0.2 255.0.0.0
ip ospf 1 area 0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 24.0.0.2 255.0.0.0
duplex auto
speed auto
!
router eigrp 100
redistribute ospf 1 metric 1000 1 255 1 1500
network 24.0.0.0
distance eigrp 90 90
no auto-summary
!
router ospf 1
log-adjacency-changes
redistribute eigrp 100 subnets
R3:

interface FastEthernet0/0
ip address 34.0.0.3 255.0.0.0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 13.0.0.3 255.0.0.0
ip ospf 1 area 0
duplex auto
speed auto
!
router eigrp 100
redistribute ospf 1 metric 25 1000 255 1 1500
network 34.0.0.0
distance eigrp 90 90
no auto-summary
!
router ospf 1
log-adjacency-changes
redistribute eigrp 100 subnets

R2#sh ip eigrp top
IP-EIGRP Topology Table for AS(100)/ID(24.0.0.2)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 12.0.0.0/8, 1 successors, FD is 2560256
via Redistributed (2560256/0)
P 13.0.0.0/8, 1 successors, FD is 2560256
via Redistributed (2560256/0)
P 24.0.0.0/8, 1 successors, FD is 281600
via Connected, FastEthernet0/1
P 34.0.0.0/8, 1 successors, FD is 307200
via 24.0.0.4 (307200/281600), FastEthernet0/1
R2#sh ip route
Codes: 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

D 34.0.0.0/8 [90/307200] via 24.0.0.4, 00:10:27, FastEthernet0/1
C 24.0.0.0/8 is directly connected, FastEthernet0/1
C 12.0.0.0/8 is directly connected, FastEthernet0/0
O 13.0.0.0/8 [110/20] via 12.0.0.1, 00:10:38, FastEthernet0/0
R2#

R3#sh ip eigrp top
IP-EIGRP Topology Table for AS(100)/ID(34.0.0.3)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 12.0.0.0/8, 1 successors, FD is 2611456
via 34.0.0.4 (2611456/2585856), FastEthernet0/0
P 13.0.0.0/8, 1 successors, FD is 102656000
via Redistributed (102656000/0)
via 34.0.0.4 (2611456/2585856), FastEthernet0/0
P 24.0.0.0/8, 1 successors, FD is 307200
via 34.0.0.4 (307200/281600), FastEthernet0/0
P 34.0.0.0/8, 1 successors, FD is 281600
via Connected, FastEthernet0/0
R3#sh ip route
Codes: 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

C 34.0.0.0/8 is directly connected, FastEthernet0/0
D 24.0.0.0/8 [90/307200] via 34.0.0.4, 00:10:51, FastEthernet0/0
D EX 12.0.0.0/8 [90/2611456] via 34.0.0.4, 00:10:44, FastEthernet0/0
C 13.0.0.0/8 is directly connected, FastEthernet0/1
R3#

dtlokee

I would review the concept of the feasibility condition and how t is used to prevent routing loops , that may help you understand what the router is doing.

PStefanov

Thanks a lot! I completely forgot to think about the FC.
Thanks everyone!

Pavel

Edit: Well, the reported distance in this case is 0 so it doesn't really matter that the FD is, this route will always meet the FC. I still can't think of a good reason for making the higher distance of the redistributed route the FD.