I’m back after so busy days in work and barely have no chances to create my labs but the small portion of my time traveling to office, lunch break and traveling back home is completely used to understand one important topics in CCIE Routing and Switching. When I started studying redistribution few years back, It is quite confusing for me to understand the whole concept especially the part on how to avoid issues arising with the redistribution of routes. Well, in my own assessment, to be able to completely master this portion of the CCIE examinations, a depth understanding of routing protocols is essential. 

On this series of my online notes for my CCIE preparations, I will be going through some depth information of the concepts of Redistribution followed by Laboratory. I will be going through on some potential scenarios of Route redistribution and the potential issues that my arise caused by redistributing routes coming from other routing domains. Two of the most common issues is optimal routing and routing loops. In real situations, network nowadays are requiring redundancy which makes it more complicated in terms of administrations.  As I’m writing this post, I’m quite excited to complete the whole series of Redistribution as this topic is quite interesting and surely will be going through in depth details analyzing the information via traceroutes, logs and pings.

Concept of Redistribution

Here will be my laboratory diagram:



My Laboratory Objective as follows:

1. Ensure that all the EIGRP routes were redistributed into the OSPF network. Set up the OSPF metrics from the default metric to 5.

2. Ensure that all the OSPF routes were redistributed into EIGRP. Used the following EIGRP metrics,
 BW = 1500, Delay = 100,  Reliability = 255, Load = 5 , MTU = 1500

3. Test the connectivity between Melbourne and Manila.


Below are my relevant configurations:

Manila#sh run | sec eigrp
router eigrp 100
 network 0.0.0.0
Manila#

 Singapore#sh run | sec eigrp
router eigrp 100
 network 192.168.12.0

Singapore#sh run | sec ospf
router ospf 200
 network 192.168.23.0 0.0.0.255 area 0
Singapore#

Melbourne#sh run | sec ospf
router ospf 200
 network 0.0.0.0 255.255.255.255 area 0
Melbourne#

As seen above, for both Manila and Melbourne, I have advertise “Any” network address that will be added on each router while for Singapore, I have both my EIGRP & OSPF networks on each respective networks.

As also been expected in Singapore router, I have both the EIGRP and OSPF routes. At the moment we did not redistributed any routes so I can only see the routes on each routing protocol network.

Singapore#show ip route eigrp
!
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 3 subnets
O        10.10.30.3 [110/65] via 192.168.23.3, 00:08:23, Serial3/1
O        10.10.40.4 [110/65] via 192.168.23.3, 00:04:30, Serial3/1
Singapore#


Now, let me fulfill the first objective which is redistributing EIGRP into OSPF.

Singapore(config)#router ospf 200
Singapore(config-router)#redistribute eigrp 100 ?
  metric       Metric for redistributed routes
  metric-type  OSPF/IS-IS exterior metric type for redistributed routes
  nssa-only    Limit redistributed routes to NSSA areas
  route-map    Route map reference
  subnets      Consider subnets for redistribution into OSPF
  tag          Set tag for routes redistributed into OSPF
 

Singapore(config-router)#redistribute eigrp 100
% Only classful networks will be redistributed
Singapore(config-router)#exit


Let’s check the routing table of Singapore. So I have only the OSPF network between Singapore and Manila. I also notice the default OSPF metric of 20 and the OSPF Administrative Distance of 110.

Melbourne#show ip route ospf
!

O E2  192.168.12.0/24 [110/20] via 192.168.23.2, 00:02:07, Serial3/1
Melbourne#


We know that Singapore have also the EIGRP routes 10.10.10.1/32 and 10.10.20.2/32. So lets redistributed them as well.

Singapore(config)#router ospf 200
Singapore(config-router)#no  redistribute eigrp 100
Singapore(config-router)#redistribute eigrp 100 subnets

So here’s my new OSPF configurations,

Singapore#sh run | sec ospf
router ospf 200
 redistribute eigrp 100 subnets
 network 192.168.23.0 0.0.0.255 area 0
Singapore#
  
We can clear the OSPF process in Singapore or Melbourne to get the immediate details of the routing table on Melbourne. So here’s the new routing entries on Melbourne router.


Melbourne#show ip route ospf
!
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 4 subnets
O E2     10.10.10.1 [110/20] via 192.168.23.2, 00:00:01, Serial3/1
O E2     10.10.20.2 [110/20] via 192.168.23.2, 00:00:01, Serial3/1
O E2  192.168.12.0/24 [110/20] via 192.168.23.2, 00:00:01, Serial3/1
Melbourne#
>> As observed, the default metrics of 20 is included on the routing updates. As you may notice, I did not set any OSPF metrics here.
>> The AD of 110 for OSPF is included as well.
>> The three EIGRP routes were exported into OSPF as External Routes as they are from other 
      routing domain, in this scenario, EIGRP. 
>> Remember the OSPF LSA Types topic. I have the three EIGRP routes as  Autonomous System 
      External Type 5 LSA’s. See the OSPF database below on Melbourne router.

Melbourne#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum Tag
10.10.10.1      192.168.23.2    502         0x80000003 0x00B646 0
10.10.20.2      192.168.23.2    508         0x80000001 0x0042B1 0
192.168.12.0    192.168.23.2    772         0x80000001 0x00F7B0 0
Melbourne#

 Another Objective which I want to accomplish here is to modify the metrics of the redistributed EIGRP routes  I want the redistributed EIGRP routes to have a metric of 5 into the OSPF routing domain. So here’s how I gonna do it,

  Singapore(config)#router ospf 200
    OSPF default metric   <<<< metric value could be between this ramge.
Singapore(config-router)#default-metric 5
Singapore(config-router)#^Z

 Now, let’s check the routing table of  Melbourne. As observed the metric have change to 5.

  Melbourne#show ip route ospf
!Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 4 subnets
O E2     10.10.10.1 [110/5] via 192.168.23.2, 00:01:44, Serial3/1
O E2     10.10.20.2 [110/5] via 192.168.23.2, 00:01:44, Serial3/1
O E2  192.168.12.0/24 [110/5] via 192.168.23.2, 00:01:44, Serial3/1
Melbourne#
 So what does this metric change means to us? As we know, OSPF metrics is COST, and it thus define how the routes will be preferred. As I’m using just a simple topology to illustrate the concepts of redistribution, the metrics which I have set is useless not until I have future laboratory which have multiple exits points for redistributed routes. I will do depth examples as well in this topic in my future post.

***********************************************************************************
Interesting Information!

When I redistribute EIGRP into OSPF, what I notice is that the same statement have appeared under the EIGRP process. Look at this…(you may what to try and see it by yourself)

Singapore#sh run | sec ospf
router ospf 200
 redistribute eigrp 100 subnets
 network 192.168.23.0 0.0.0.255 area 0
 default-metric 5
Singapore#sh run | sec eigrp
router eigrp 100
 network 192.168.12.0
 redistribute eigrp 100 subnets
Singapore#
 
***********************************************************************************
 Now, what if I wanted to reach the EIGRP networks from my Loopbacks in Melbourne. Definitely, this will not work since I only have One-way Redistribution.

Let’s try to check now. As we can see, I have the routes to 10.10.10.1 but I cannot reach it via Ping!

Melbourne#show ip route 10.10.10.1
Routing entry for 10.10.10.1/32
  Known via “ospf 200″, distance 110, metric 5, type extern 2, forward metric 64
  Last update from 192.168.23.2 on Serial3/1, 00:13:16 ago
  Routing Descriptor Blocks:
  * 192.168.23.2, from 192.168.23.2, 00:13:16 ago, via Serial3/1
      Route metric is 5, traffic share count is 1
Melbourne#ping 10.10.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:
…..
Success rate is 0 percent (0/5)

 Let me go ahead and set up Singapore router to complete the third objective of this Lab. I want full connectivity of the network between Melbourne and Manila. To do this, I will be redistributing OSPF Routes into EIGRP.

But before that I wanted to add a Loopback address on Singapore and add it to EIGRP networks to show one concept.

 Singapore(config)#int lo2
Singapore(config-if)#ip address 10.10.50.2 255.255.255.255
Singapore(config-if)#exit
Singapore(config)#router eigrp 100
Singapore(config-router)#network 10.10.50.2 0.0.0.0
Singapore(config-router)#

Let me check the Manila routing information. I have the EIGRP routes from Singapore.

Manila#show ip route eigrp
!
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 3 subnets
D        10.10.50.2 [90/2297856] via 192.168.12.2, 00:01:11, Serial3/0
Manila#

We know that Singapore have this routes below and what I want is to transfer to EIGRP routes.

Singapore#show ip route ospf
!
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 5 subnets
O        10.10.30.3 [110/65] via 192.168.23.3, 00:58:11, Serial3/1
O        10.10.40.4 [110/65] via 192.168.23.3, 00:58:11, Serial3/1
Singapore#


So configuring Singapore to redistribute the OSPF routes,

Singapore(config)#router eigrp 100
Singapore(config-router)#redistribute ospf 200 ?
  match      Redistribution of OSPF routes
  metric     Metric for redistributed routes
  route-map  Route map reference
 
Singapore(config-router)#redistribute ospf 200  <<< I just choose to redistribute OSPF 200. Period!
Singapore(config-router)#

Important!!! 
So let me check the routing table of Manila. Again, it does proves the characteristics of Redistributed Routes into EIGRP that if we don’t specify the metrics, it will not be showing into the routing table. Remember the default metrics of EIGRP is Infinity and we know  that any networks redistributed into EIGRP without setting the metrics will not appear on the routing table.

Manila#show ip route eigrp
!
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 3 subnets
D        10.10.50.2 [90/2297856] via 192.168.12.2, 00:07:29, Serial3/0
Manila#

 Let’s correct this by adding the a default-metrics under EIGRP process.

Singapore(config)#router eigrp 100
 Singapore(config-router)#default-metric ?
    Bandwidth in Kbits per second  <<< Metric is Bandwidth

Singapore(config-router)#default-metric 1500 ?      
    delay metric in 10 microsecond units   <<< The Second Metric is Delay

Singapore(config-router)#default-metric 1500 100 ?
    Reliability metric where 255 is 100% reliable    <<< The Third metric is Reliability

Singapore(config-router)#default-metric 1500 100 255 ?
    Effective bandwidth metric (Loading) where 255 is 100% loaded  << The fourth metric is Load

Singapore(config-router)#default-metric 1500 100 255 5 ?
    Maximum Transmission Unit metric of the path  <<< The fifth metric is MTU

Singapore(config-router)#default-metric 1500 100 255 5 1500
Singapore(config-router)#

So here’s my EIGRP configs now on Singapore,

 Singapore#sh run | sec eigrp
router eigrp 100
 default-metric 1500 100 255 5 1500
 network 10.10.50.2 0.0.0.0
 network 192.168.12.0
 redistribute ospf 200   <<<<<<<<<
 redistribute eigrp 100 subnets

As also notice the OSPF configurations were updated when I redistributed OSPF into EIGRP. 

Singapore#sh run | sec ospf
 redistribute ospf 200
router ospf 200      <<<<<<<< This appears under OSPF when I applied this under EIGRP.
 redistribute eigrp 100 subnets
 network 192.168.23.0 0.0.0.255 area 0
 default-metric 5
Singapore#

Now, let’s take a look into my Manila routing details. So sweet right!!! I have now the OSPF networks into my EIGRP networks.

Manila#show ip route eigrp
!
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 5 subnets
D EX     10.10.30.3 [170/2244096] via 192.168.12.2, 00:03:47, Serial3/0
D EX     10.10.40.4 [170/2244096] via 192.168.12.2, 00:03:47, Serial3/0
D        10.10.50.2 [90/2297856] via 192.168.12.2, 00:13:52, Serial3/0
D EX  192.168.23.0/24 [170/2244096] via 192.168.12.2, 00:03:47, Serial3/0
Manila#


Important!!!

>>  The D EX means that I have external EIGRP routes. 
>>  The 170/2244096 means  Administrative Distance / Metrics. So I will keep in mind that External EIGRP networks have an Administrative Distance of 170.
>> The  Metrics of  2244096 is the cumulative metrics of the EIGRP ( BW, DL, RL, LD, MTU)
>> The D means Internal EIGRP routes have an AD of 90.

So let’s finally check the connectivity,

Manila#ping 10.10.30.3 source 10.10.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.30.3, timeout is 2 seconds:
Packet sent with a source address of 10.10.10.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 96/102/108 ms


Manila#ping 10.10.40.4 source 10.10.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.40.4, timeout is 2 seconds:
Packet sent with a source address of 10.10.10.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 88/107/164 ms
Manila#


As I have the complete end to end connectivity, I have the Two-Way Redistribution.  It means that I’m redistributing both routing domain to each other via the Singapore router. Singapore router acts as the One Point Redistribution router as it controls both the EIGRP and OSPF routing domains. In my example above, I have EIGRP redistributed into OSPF and vice-versa.


Here are my learning points:

A.   EIGRP —> OSPF  Redistribution:

router ospf
redistribute eigrp subnets

Note: 
a.  The default metric is 20. SO it is not necessary to set up the metrics unless specified.
b. The metric can be change by using the command  default-metric
c. OSPF AD is 110
d.  Imported (Redistributed) routes into OSPF were considered as Type 5 AS External LSA.

B. OSPF —> EIGRP Redistribution:

router eigrp
distribute ospf
default-metric

Note:
a. External EIGRP AD is 170
b. Internal EIGRP AD is 90

*** This ends my first post about Route Redistribution***

Share this:

• LinkedIn
• X
• Facebook
• Tumblr
• Pinterest
• Email
• Reddit
• Telegram
• WhatsApp

Like Loading…