Optimal path routing using distance eigrp 90 105 command

Answered Question
Mar 25th, 2012

Hi all,

I  was studying this Routing video  for redistribution using 2 Routers.

Here is topology ***************************

R4 is running EIGRP  only.

R2 and R3 are both running ospf and EIGRP and are redistribution routers.

R2 and R3 have fast ethernet and serial connection to R1

R1 is running OSPF  only.

I have applied the redistribution fine on both R2 and R3.

Now R4 is learning OSPF  routes  and R1 is learning  EIGPR  question.

Traffic Flow***********************************

For R4 to reach network 10.1.0.1  which is loopback of R1 (Running OSPF)   it   goes  via 

R4  R2   R1.

Question ********************

We need to change the path so that traffic from R4 to R1 goes via R3.

R4  R2   R3  R1

Steps   taken in video***************************************

router eigrp 100

redistribute ospf 1 route-map OSPF-TO-EIGRP

network 10.1.23.0 0.0.0.255

network 10.1.24.0 0.0.0.255

distance eigrp 90 105*********************************************************************************

Before this change

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

     10.0.0.0/8 is variably subnetted, 10 subnets, 2 masks
O       10.1.13.0/24 [110/65] via 10.1.12.1, 00:21:10, FastEthernet0/0
C       10.1.12.0/24 is directly connected, FastEthernet0/0
D       10.4.4.0/24 [90/2297856] via 10.1.24.4, 00:21:04, Serial0/0
O       10.1.0.1/32 [110/2] via 10.1.12.1, 00:21:10, FastEthernet0/0
D       10.4.2.0/24 [90/2297856] via 10.1.24.4, 00:21:04, Serial0/0
D       10.4.3.0/24 [90/2297856] via 10.1.24.4, 00:21:04, Serial0/0
D       10.4.0.0/24 [90/2297856] via 10.1.24.4, 00:21:04, Serial0/0
D       10.4.1.0/24 [90/2297856] via 10.1.24.4, 00:21:04, Serial0/0
C       10.1.24.0/24 is directly connected, Serial0/0
C       10.1.23.0/24 is directly connected, Serial0/1

After distance command is added

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

     10.0.0.0/8 is variably subnetted, 10 subnets, 2 masks
D EX    10.1.13.0/24 [105/6917120] via 10.1.23.3, 00:18:34, Serial0/1?????????????????????????????????????????????????
C       10.1.12.0/24 is directly connected, FastEthernet0/0
D       10.4.4.0/24 [90/2297856] via 10.1.24.4, 00:18:36, Serial0/0
D EX    10.1.0.1/32 [105/6917120] via 10.1.23.3, 00:18:34, Serial0/1*************************************************************
D       10.4.2.0/24 [90/2297856] via 10.1.24.4, 00:18:36, Serial0/0
D       10.4.3.0/24 [90/2297856] via 10.1.24.4, 00:18:36, Serial0/0
D       10.4.0.0/24 [90/2297856] via 10.1.24.4, 00:18:36, Serial0/0
D       10.4.1.0/24 [90/2297856] via 10.1.24.4, 00:18:36, Serial0/0
C       10.1.24.0/24 is directly connected, Serial0/0
C       10.1.23.0/24 is directly connected, Serial0/1
R2#

R2#  sh ip route 10.1.0.1   *******************************************************************Loopback of R1

Routing entry for 10.1.0.1/32

  Known via "eigrp 100", distance 105, metric 6917120

  Tag 40, type external  ???????????????????

  Redistributing via eigrp 100, ospf 1

  Last update from 10.1.23.3 on Serial0/1, 00:19:16 ago

  Routing Descriptor Blocks:

  * 10.1.23.3, from 10.1.23.3, 00:19:16 ago, via Serial0/1

      Route metric is 6917120, traffic share count is 1

      Total delay is 20200 microseconds, minimum bandwidth is 400 Kbit

      Reliability 255/255, minimum MTU 1500 bytes

      Loading 1/255, Hops 1

My question is   for above command it shows type external this is because we have changed AD  of EIGRP  external routes  to 105???

thats why it shows external there?

Also When we do sh ip route on R2

Question 2

Before  using distance command

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

     10.0.0.0/8 is variably subnetted, 10 subnets, 2 masks
O       10.1.13.0/24 [110/65] via 10.1.12.1, 00:21:10, FastEthernet0/0???????????????????????????????????????????????????

After using distance command on R2

it shows D EX    10.1.13.0/24 [105/6917120] via 10.1.23.3, 00:18:34, Serial0/1?????????????????????????????????????????????????

This shows EIGRP external routes for 10.1.13.0 even though it has direct connection to R1 using OSPF why it shows D EX now ??

Many thanks

MAhesh

I have this problem too.
0 votes
Correct Answer by Reza Sharifi about 2 years 2 weeks ago

Hi Mahesh,

Your observation is correct.  In your first scenario before adding the distance EIGRP command the primary route to get to

10.1.0.1  and 10.1.13.0 is using OSPF (as you mentioned), but if you look at the EIGRP routing table on r2 (sho ip route eigrp) , you should be able to see routes to 10.1.0.1  and 10.1.13.0, but will not be active.

HTH

Correct Answer by vijay.swaminathan about 2 years 2 weeks ago

The route for the network 10.0.1.0 (R1's loopback) is received from R1 as well as R3. (R3 receives this route via redistribution of OSPF routes into EIGRP).

On R2 the above said network is received as a OSPF Route which has the AD of 110 and received as a External EIGRP route from R3.

so to answer your question, it is shown as External because it is a OSPF route redistributed into EIGRP and not because of AD.

it is shown in Routing Table because of its AD because the same network is advertised into R2 with AD as 110 (OSPF) and 105 (D Ex) so the route with lowest AD wins

Hope this answers your question 1.:

To answer your question 2:

10.1.13.0 is not directly connected to R2. I hope this is the connection between R1 and R3 and known via OSPF and EIGRP (External Route) - as stated above.

so Route wiht Lowest AD wins and shwon in the routing table as D EX.

HTH

-Vijay

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Reza Sharifi Sun, 03/25/2012 - 08:30

Hi Mahesh,

Can you provide diagram of your network and point out which devices are running what protocols?

Thanks,

Reza

mahesh18 Sun, 03/25/2012 - 08:36

Hi Reza,

Thanks for reply.

Diagram is attached under original post.

mahesh18 Sun, 03/25/2012 - 09:04

Hi Reza,

R4 is running eigrp

R2and R3 are running ospf and

Eigrp.

they are redistributing routers.

R1 is running ospf only.

Thanks

Correct Answer
vijay.swaminathan Sun, 03/25/2012 - 09:25

The route for the network 10.0.1.0 (R1's loopback) is received from R1 as well as R3. (R3 receives this route via redistribution of OSPF routes into EIGRP).

On R2 the above said network is received as a OSPF Route which has the AD of 110 and received as a External EIGRP route from R3.

so to answer your question, it is shown as External because it is a OSPF route redistributed into EIGRP and not because of AD.

it is shown in Routing Table because of its AD because the same network is advertised into R2 with AD as 110 (OSPF) and 105 (D Ex) so the route with lowest AD wins

Hope this answers your question 1.:

To answer your question 2:

10.1.13.0 is not directly connected to R2. I hope this is the connection between R1 and R3 and known via OSPF and EIGRP (External Route) - as stated above.

so Route wiht Lowest AD wins and shwon in the routing table as D EX.

HTH

-Vijay

mahesh18 Sun, 03/25/2012 - 10:08

Hi Vijay,

Thanks for reply.

So here is what i understood

R2 is learning the routes 10.1.0.1  and 10.1.13.0 

before the distance command***************

It shows its learning these by R1  as R1  has AD  of 110 thats why it shows both above routes  in Routing table of R2  correct?

It also learns these routes by R3  -- but they have higher AD  of D  EX  170 thats why its not in routing table of R2.correct?

After we use distance command on R2

Now as EIGRP external metric is 105 now which is also below 110 OSPF  R2 learn these routes from R3 as OSPF is

redistributed into EIGRP right???

Thats why it changes OSPF connection to D EX  when we do sh ip route right?

Thanks

mahesh

R2 learns both routes 10.1.0.1 and 10.1.13.0  from R1 

Correct Answer
Reza Sharifi Sun, 03/25/2012 - 16:55

Hi Mahesh,

Your observation is correct.  In your first scenario before adding the distance EIGRP command the primary route to get to

10.1.0.1  and 10.1.13.0 is using OSPF (as you mentioned), but if you look at the EIGRP routing table on r2 (sho ip route eigrp) , you should be able to see routes to 10.1.0.1  and 10.1.13.0, but will not be active.

HTH

mahesh18 Mon, 03/26/2012 - 00:20

Hi Reza,

Thanks for reply.

I check the R2  and did sh ip route EIGRP 

before using the distance command

R2#sh ip eigrp topology
IP-EIGRP Topology Table for AS(100)/ID(10.1.12.1)

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

P 10.1.13.0/24, 1 successors, FD is 6405120, tag is 40
        via Redistributed (6405120/0)*****************************************************
P 10.1.12.0/24, 1 successors, FD is 6405120, tag is 40
        via Redistributed (6405120/0)
P 10.4.4.0/24, 1 successors, FD is 2297856
        via 10.1.24.4 (2297856/128256

P 10.1.0.1/32, 1 successors, FD is 6405120, tag is 40

        via Redistributed (6405120/0)****************************************************************

Question  ---so Routes which  are shown as P  10.1.13.0  and 10.1.0.1  are Feasible successor???

sh ip route shows

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

     10.0.0.0/8 is variably subnetted, 10 subnets, 2 masks
O       10.1.13.0/24 [110/65] via 10.1.12.1, 00:10:42, FastEthernet0/0

O       10.1.0.1/32 [110/2] via 10.1.12.1, 00:10:42, FastEthernet0/0

So we can see that the OSPF  routes are in Routing table as they have lower AD.

Also we see same routes redistribute into EIGRP  and shows as passive in EIGRP  topology.

*****************************************************************************************************************************

Here is what i did i turn off  int fa0/0  of R2 as it connects to R1.

Did sh ip route

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

     10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
D EX    10.1.13.0/24 [170/6917120] via 10.1.23.3, 00:01:17, Serial0/1
D       10.4.4.0/24 [90/2297856] via 10.1.24.4, 00:19:56, Serial0/0
D EX    10.1.0.1/32 [170/6917120] via 10.1.23.3, 00:01:17, Serial0/1

Now it learn the routes by External EIGRP.

did sh ip eigrp  topology

R2# sh ip eigrp topology
IP-EIGRP Topology Table for AS(100)/ID(10.1.12.1)

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

P 10.1.13.0/24, 1 successors, FD is 6917120, tag is 40
        via 10.1.23.3 (6917120/6405120), Serial0/1
P 10.1.0.1/32, 1 successors, FD is 6917120, tag is 40
        via 10.1.23.3 (6917120/6405120), Serial0/1

Question 2  does above topology table means that R2 has any feasible successor or back up route now?

Thanks

MAhesh

vijay.swaminathan Mon, 03/26/2012 - 01:09

What ever routes that appears on the "Show ip eigrp topology" table are either successor / feasible successor.

so to answer your question 1, they are actually successors.

R2 has two routes to the entwork 10.1.0.1/32. One through OSPF and the other through EIGRP External Route.

since OSPF has the lower AD, that gets installed in the routing table . so R2 has a Back Up route learnt via EIGRP for the network 10.1.0.1/32

HTH

-Vijay    

mahesh18 Mon, 03/26/2012 - 11:20

Hi Vijay and Reza,

Many thanks for answering my question.

Now everything is clear to me.

Regards

Mahesh

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Posted March 25, 2012 at 7:45 AM
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