The BIG lab – Part 6 – Route Redistribution (2.90)

We have now reached part 6 of this series, we have OSPF, RIP and EIGRP working in our network, but at the moment these networks are all self-contained and have visibility only within their own routing processes. So lets do some redistribution between them and get all of our networks talking to each other and have some end-to-end visibilty.

We will redistribute OSPF into RIP and EIGRP into RIP, and hopefully at the end of this post we should have working routes all the way from R1 (OSPF) through our RIP routers all the way over to R10 (EIGRP).

So what is redistribution? Well, hopefully you have already covered this in the CCNP, but if not (and hopefully this series has been a good start for those doing the CCNA, CCNP or CCIE), then we’ll briefly cover the basics of redistribution before we put this into our topology.

Route Redistribution

In small scale networks it’s often the case that one routing protocol is used, as the networks grow, and expand there may be the need (such as migrating from one routing protocol to another) that different IGPs are used. Route redistribution allows for routes from one routing protocol to be advertised into another. These redistributed routes will be learned as external routes, and as such usually have a higher (therefore less preferred) metric to the local routes.

For redistribution to work we need a router to run both routing protocols, having one interface in each of the different routing domains.

In our topology R4 will handle redistribution between OSPF and RIP, and both R4 and R5 will handle redistribution between RIP and EIGRP. It is the redistribution between RIP and EIGRP that will cause us some potential issues, and to understand why we need to have a quick look at Administrative Distances.

Administrative Distances

The default Administrative Distances (AD) are as follows, and the ones we need to concern ourselves with are bolded:

Routing Protocol Administrative Distance
Connected interface 0
Static route 1
EIGRP Summary route 5
External BGP 20
Internal EIGRP 90
IGRP 100
OSPF 110
IS-IS 115
RIP 120
EGP 140
ODR 160
External EIGRP 170
Internal BGP 200

Because OSPF into RIP only has one redistribution point (R4) then we will be OK, but because EIGRP into RIP has two redistribution points (R4 and R5) we will have EIGRP summary routes (that we set up in the previous lab) with an AD of 5, Internal EIGRP (on R4 and R5) with an AD of 90 being redistributed into RIP (AD of 120), and it is these internal EIGRP routes that might cause us an issue, as lower AD is preferred. In short we have the potential for a routing loop. If we do encounter any issues then we can look at distribution-lists or route-tagging to overcome any issues. I have covered routing loops before, so this will be a good refresher. Like they say though the proof is in the pudding, so let’s get on and get started.

Redistributing RIP into EIGRP

EIGRP uses bandwidth and delay as its main metrics, but will also use reliability, load and MTU.

We start by entering the EIGRP process on R5

R5(config)#router eigrp 10
R5(config-router)#redistribute rip ?
     metric     Metric for redistributed routes
     route-map  Route map reference
R5(config-router)#redistribute rip metric ?
     <1-4294967295>  Bandwidth metric in Kbits per second

The first metric we need to set is the bandwidth, so lets set this as 10000. The next next metric is delay, which we will set at 1000

R5(config-router)#redistribute rip metric 10000 ?
      <0-4294967295>  EIGRP delay metric, in 10 microsecond units

Thankfully IOS is very helpful and gives us a good idea for how we should set our metrics. So for the next metric, which is reliability we know that 255 is the most reliable

R5(config-router)#redistribute rip metric 10000 1000 ?
     <0-255>  EIGRP reliability metric where 255 is 100% reliable

And for load we should set it at the lowest possible (1)

R5(config-router)#redistribute rip metric 10000 1000 255 ?
     <1-255>  EIGRP Effective bandwidth metric (Loading) where 255 is 100% loaded

Lastly we can set the MTU at 1500.

R5(config-router)#redistribute rip metric 10000 1000 255 1 ?
     <1-65535>  EIGRP MTU of the path

And thats it the full command would be:

R5(config-router)#redistribute rip metric 10000 1000 255 1 1500

We do the same on R4:

R4(config)#router eigrp 10
R4(config-router)#redistribute rip metric 10000 1000 255 1 1500
R4(config-router)#exit
R4(config)#exit

Redistributing EIGRP into RIP

Not much has, so far, changed within our routing tables on R4 or R5, which is not overly surprising. So let’s redistribute EIGRP into RIP. The commands to use are:

R5(config)#router rip
R5(config-router)#redistribute eigrp 10 metric 2
R5(config-router)#exit
R5(config)#exit

And this is identical for R4 The command specifies that we are redistributing eigrp AS 10 into RIP and setting the metric (and RIP only uses hop count for its calculations) at 2. If a metric is not supplied RIP will assume a metric of 0 and will not advertise the redistributed routes.

Confirming mutual redistribution between RIP and EIGRP

R6 is a good router to look at to check for our redistributed EIGRP routes. Without any redistribution the routing table for R6 looks like this:

R6#sh ip route | beg Gate
Gateway of last resort is not set       
   10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
R        10.20.1.0/24 [120/1] via 10.20.2.1, 00:00:00, Serial0/0
C        10.20.2.0/24 is directly connected, Serial0/0
L        10.20.2.2/32 is directly connected, Serial0/0
R        10.35.1.0/24 [120/1] via 10.20.2.1, 00:00:00, Serial0/0

(Note that R7 is currently turned off…)

After redistributing RIP into EIGRP, and EIGRP into RIP, the routing table on R6 looks like this:

R6#sh ip route | beg Gate
Gateway of last resort is not set       
   10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
R        10.20.1.0/24 [120/1] via 10.20.2.1, 00:00:00, Serial0/0
C        10.20.2.0/24 is directly connected, Serial0/0
L        10.20.2.2/32 is directly connected, Serial0/0
R        10.25.1.0/24 [120/2] via 10.20.2.1, 00:00:00, Serial0/0
R        10.30.1.0/24 [120/2] via 10.20.2.1, 00:00:00, Serial0/0
R        10.31.1.0/24 [120/2] via 10.20.2.1, 00:00:00, Serial0/0
R        10.35.1.0/24 [120/1] via 10.20.2.1, 00:00:00, Serial0/0      
   172.20.0.0/16 is variably subnetted, 3 subnets, 2 masks
R        172.20.20.0/24 [120/2] via 10.20.2.1, 00:00:00, Serial0/0
R        172.20.30.0/24 [120/2] via 10.20.2.1, 00:00:00, Serial0/0
R        172.20.40.0/23 [120/2] via 10.20.2.1, 00:00:00, Serial0/0

So we can see that R6 which is just running RIP, now knows of the EIGRP network, and has learned the EIGRP routes through our redistribution, and they have an AD of 120, and a hop count of 2We can also look at R10 to see the effects of redistribution. 

Before we started to redistribute the routing table of R10 looked like this:

R10#sh ip route | beg Gate
Gateway of last resort is not set       
   10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
D        10.20.1.0/24 [90/3193856] via 10.31.1.1, 00:02:23, Serial1/0
D        10.20.2.0/24 [90/3705856] via 10.31.1.1, 00:02:23, Serial1/0
D        10.25.1.0/24 [90/2681856] via 10.31.1.1, 00:02:23, Serial1/0
D        10.30.1.0/24 [90/2681856] via 10.31.1.1, 00:02:23, Serial1/0
C        10.31.1.0/24 is directly connected, Serial1/0
L        10.31.1.2/32 is directly connected, Serial1/0
D        10.35.1.0/24 [90/41536000] via 10.31.1.1, 00:02:23, Serial1/0       
   172.20.0.0/16 is variably subnetted, 9 subnets, 3 masks
C        172.20.20.0/24 is directly connected, Loopback0
L        172.20.20.1/32 is directly connected, Loopback0
C        172.20.30.0/24 is directly connected, Loopback1
L        172.20.30.1/32 is directly connected, Loopback1
D        172.20.40.0/23 is a summary, 00:02:25, Null0
C        172.20.40.0/24 is directly connected, Loopback2
L        172.20.40.1/32 is directly connected, Loopback2
C        172.20.41.0/24 is directly connected, Loopback3
L        172.20.41.1/32 is directly connected, Loopback3

And once we turn on R7 it now looks like this:

R10#sh ip route | beg Gate
Gateway of last resort is not set       
   10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
D        10.20.1.0/24 [90/3193856] via 10.31.1.1, 00:19:27, Serial1/0
D        10.20.2.0/24 [90/3705856] via 10.31.1.1, 00:19:27, Serial1/0
D EX     10.20.3.0/24 [170/2937856] via 10.31.1.1, 00:06:31, Serial1/0
D        10.25.1.0/24 [90/2681856] via 10.31.1.1, 00:19:27, Serial1/0
D        10.30.1.0/24 [90/2681856] via 10.31.1.1, 00:19:27, Serial1/0
C        10.31.1.0/24 is directly connected, Serial1/0
L        10.31.1.2/32 is directly connected, Serial1/0
D        10.35.1.0/24 [90/41536000] via 10.31.1.1, 00:19:27, Serial1/0
D EX     10.60.1.0/24 [170/2937856] via 10.31.1.1, 00:06:12, Serial1/0       
   172.20.0.0/16 is variably subnetted, 9 subnets, 3 masks
C        172.20.20.0/24 is directly connected, Loopback0
L        172.20.20.1/32 is directly connected, Loopback0
C        172.20.30.0/24 is directly connected, Loopback1
L        172.20.30.1/32 is directly connected, Loopback1
D        172.20.40.0/23 is a summary, 00:19:44, Null0
C        172.20.40.0/24 is directly connected, Loopback2
L        172.20.40.1/32 is directly connected, Loopback2
C        172.20.41.0/24 is directly connected, Loopback3
L        172.20.41.1/32 is directly connected, Loopback3
We can see that R7 has the following IP addresses assigned to it:
R7#sh ip int bri
Interface          IP-Address  OK? Method  Status                           Protocol
Serial0/0         unassigned YES TFTP      administratively down down
Serial0/1         10.20.3.2     YES TFTP      up                                 up
Serial0/2         unassigned YES TFTP      administratively down down
Serial0/3         unassigned YES TFTP      administratively down down
Loopback0     10.60.1.1     YES TFTP      up                                 up

So R10 now knows of both the 10.20.3.0/24 network and the 10.60.1.0/24 network, and that they are being advertised as an EIGRP External (D EX) with an AD of 170. We can confirm reachability as well:

R10#ping 10.60.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.60.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 44/44/48 ms
R10#

Mutual redistribution of RIP and OSPF

Lets start by redistributing RIP into OSPF
R2’s current routing table looks like this (with R12, R13 and R14 turned off – due to not wanting to completely drain my laptop resources):

R2#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.2.3.0/24 is directly connected, Multilink1
L        1.2.3.5/32 is directly connected, Multilink1
      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C        10.1.1.0/24 is directly connected, Serial0/2
L        10.1.1.1/32 is directly connected, Serial0/2
O IA     10.1.2.0/24 [110/128] via 10.1.1.2, 00:04:00, Serial0/2
C        10.1.6.0/24 is directly connected, Serial0/3
L        10.1.6.1/32 is directly connected, Serial0/3
O IA     10.10.1.0/24 [110/33] via 1.2.3.4, 00:04:00, Multilink1

We can see that we have some OSPF Inter-Area routes (denoted by O IA).

Once R4 is added to the OSPF domain via it’s s0/0 interface in area 3, the routing table looks like this:

R4#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/24 is subnetted, 1 subnets
O IA     1.2.3.0 [110/96] via 10.1.6.1, 00:01:41, Serial0/0
      10.0.0.0/8 is variably subnetted, 15 subnets, 2 masks
O IA     10.1.1.0/24 [110/128] via 10.1.6.1, 00:01:41, Serial0/0
O IA     10.1.2.0/24 [110/192] via 10.1.6.1, 00:01:41, Serial0/0
C        10.1.6.0/24 is directly connected, Serial0/0
L        10.1.6.2/32 is directly connected, Serial0/0
O IA     10.10.1.0/24 [110/97] via 10.1.6.1, 00:01:41, Serial0/0
C        10.20.1.0/24 is directly connected, Serial0/1
L        10.20.1.1/32 is directly connected, Serial0/1
D        10.20.2.0/24 [90/2681856] via 10.20.1.2, 00:02:09, Serial0/1
R        10.20.3.0/24 [120/2] via 10.20.1.2, 00:00:06, Serial0/1
C        10.25.1.0/24 is directly connected, Serial0/2
L        10.25.1.1/32 is directly connected, Serial0/2
D        10.30.1.0/24 [90/2681856] via 10.25.1.2, 00:02:13, Serial0/2
D        10.31.1.0/24 [90/2681856] via 10.25.1.2, 00:02:13, Serial0/2
D        10.35.1.0/24 [90/41024000] via 10.20.1.2, 00:02:13, Serial0/1
R        10.60.1.0/24 [120/3] via 10.20.1.2, 00:00:10, Serial0/1
      172.20.0.0/16 is variably subnetted, 3 subnets, 2 masks
D        172.20.20.0/24 [90/2809856] via 10.25.1.2, 00:02:13, Serial0/2
D        172.20.30.0/24 [90/2809856] via 10.25.1.2, 00:02:13, Serial0/2
D        172.20.40.0/23 [90/2809856] via 10.25.1.2, 00:02:13, Serial0/2
R4(config)#router rip
R4(config-router)#redistribute ospf 1 metric 2
R6’s routing table now looks like this:

R6#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/24 is subnetted, 1 subnets
R        1.2.3.0 [120/3] via 10.20.2.1, 00:00:28, Serial0/0
      10.0.0.0/8 is variably subnetted, 14 subnets, 2 masks
R        10.1.1.0/24 [120/3] via 10.20.2.1, 00:00:28, Serial0/0
R        10.1.2.0/24 [120/3] via 10.20.2.1, 00:00:28, Serial0/0
R        10.1.6.0/24 [120/2] via 10.20.2.1, 00:00:28, Serial0/0
R        10.10.1.0/24 [120/3] via 10.20.2.1, 00:00:28, Serial0/0
R        10.20.1.0/24 [120/1] via 10.20.2.1, 00:00:28, Serial0/0
C        10.20.2.0/24 is directly connected, Serial0/0
L        10.20.2.2/32 is directly connected, Serial0/0
C        10.20.3.0/24 is directly connected, Serial0/1
L        10.20.3.1/32 is directly connected, Serial0/1
R        10.25.1.0/24 [120/2] via 10.20.2.1, 00:00:28, Serial0/0
R        10.30.1.0/24 [120/2] via 10.20.2.1, 00:00:28, Serial0/0
R        10.31.1.0/24 [120/2] via 10.20.2.1, 00:00:28, Serial0/0
R        10.35.1.0/24 [120/1] via 10.20.2.1, 00:00:28, Serial0/0
R        10.60.1.0/24 [120/1] via 10.20.3.2, 00:00:05, Serial0/1
      172.20.0.0/16 is variably subnetted, 3 subnets, 2 masks
R        172.20.20.0/24 [120/2] via 10.20.2.1, 00:00:28, Serial0/0
R        172.20.30.0/24 [120/2] via 10.20.2.1, 00:00:28, Serial0/0
R        172.20.40.0/23 [120/2] via 10.20.2.1, 00:00:28, Serial0/0

And R10’s looks like this:

R10#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/24 is subnetted, 1 subnets
D EX     1.2.3.0 [170/41792000] via 10.31.1.1, 00:01:58, Serial1/0
      10.0.0.0/8 is variably subnetted, 13 subnets, 2 masks
D EX     10.1.1.0/24 [170/41792000] via 10.31.1.1, 00:01:58, Serial1/0
D EX     10.1.2.0/24 [170/41792000] via 10.31.1.1, 00:01:58, Serial1/0
D        10.1.6.0/24 [90/3193856] via 10.31.1.1, 00:05:50, Serial1/0
D EX     10.10.1.0/24 [170/41792000] via 10.31.1.1, 00:01:58, Serial1/0
D        10.20.1.0/24 [90/3193856] via 10.31.1.1, 00:40:20, Serial1/0
D        10.20.2.0/24 [90/3705856] via 10.31.1.1, 00:40:20, Serial1/0
D EX     10.20.3.0/24 [170/2937856] via 10.31.1.1, 00:27:24, Serial1/0
D        10.25.1.0/24 [90/2681856] via 10.31.1.1, 00:40:20, Serial1/0
D        10.30.1.0/24 [90/2681856] via 10.31.1.1, 00:40:20, Serial1/0
C        10.31.1.0/24 is directly connected, Serial1/0
L        10.31.1.2/32 is directly connected, Serial1/0
D        10.35.1.0/24 [90/41536000] via 10.31.1.1, 00:40:20, Serial1/0
D EX     10.60.1.0/24 [170/2937856] via 10.31.1.1, 00:27:05, Serial1/0
      172.20.0.0/16 is variably subnetted, 9 subnets, 3 masks
C        172.20.20.0/24 is directly connected, Loopback0
L        172.20.20.1/32 is directly connected, Loopback0
C        172.20.30.0/24 is directly connected, Loopback1
L        172.20.30.1/32 is directly connected, Loopback1

So R6 has learnt of the routes through RIP, and R10 has learnt of the OSPF routes via EIGRP.

Now lets send our RIP routes (and hopefully all of the redistributed EIGRP routes) into OSPF.

Before redistribution R1’s routing table looks like this:

R1#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.2.3.0/24 is directly connected, Multilink1
L        1.2.3.4/32 is directly connected, Multilink1
      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O        10.1.1.0/24 [110/96] via 1.2.3.5, 00:00:51, Multilink1
O IA     10.1.2.0/24 [110/160] via 1.2.3.5, 00:00:47, Multilink1
C        10.10.1.0/24 is directly connected, Loopback0
L        10.10.1.1/32 is directly connected, Loopback0
R4(config)#router ospf 1
R4(config-router)#redistribute rip subnets metric 2000
R1#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.2.3.0/24 is directly connected, Multilink1
L        1.2.3.4/32 is directly connected, Multilink1
      10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O        10.1.1.0/24 [110/96] via 1.2.3.5, 00:23:34, Multilink1
O IA     10.1.2.0/24 [110/160] via 1.2.3.5, 00:23:30, Multilink1
O IA     10.1.6.0/24 [110/96] via 1.2.3.5, 00:15:30, Multilink1
C        10.10.1.0/24 is directly connected, Loopback0
L        10.10.1.1/32 is directly connected, Loopback0
O E2     10.20.1.0/24 [110/20] via 1.2.3.5, 00:00:45, Multilink1
O E2     10.20.3.0/24 [110/20] via 1.2.3.5, 00:00:45, Multilink1
O E2     10.25.1.0/24 [110/20] via 1.2.3.5, 00:00:45, Multilink1
O E2     10.60.1.0/24 [110/20] via 1.2.3.5, 00:00:45, Multilink1

And now we can see that R1 has learnt of the RIP routes as OSFP External Type 2, but not the EIGRP, so lets just do the last couple of redistribution commands:
R4(config)#router eigrp 10
R4(config-router)#redistribute ospf 1 metric 10000 1000 255 1 1500
R4(config-router)#router ospf 1
R4(config-router)#redistribute eigrp 10 subnets metric 2222
R4(config-router)#exit
R4(config)#exit
And now we can see, using R1, R7 and R10 (as these are on the periphery of our network) that we have full reachability:

R1#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        1.2.3.0/24 is directly connected, Multilink1
L        1.2.3.4/32 is directly connected, Multilink1
      10.0.0.0/8 is variably subnetted, 13 subnets, 2 masks
O        10.1.1.0/24 [110/96] via 1.2.3.5, 00:43:07, Multilink1
O IA     10.1.2.0/24 [110/160] via 1.2.3.5, 00:43:03, Multilink1
O IA     10.1.6.0/24 [110/96] via 1.2.3.5, 00:35:03, Multilink1
C        10.10.1.0/24 is directly connected, Loopback0
L        10.10.1.1/32 is directly connected, Loopback0
O E2     10.20.1.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     10.20.2.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     10.20.3.0/24 [110/2000] via 1.2.3.5, 00:17:35, Multilink1
O E2     10.25.1.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     10.30.1.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     10.31.1.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     10.35.1.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     10.60.1.0/24 [110/2000] via 1.2.3.5, 00:17:35, Multilink1
      172.20.0.0/16 is variably subnetted, 3 subnets, 2 masks
O E2     172.20.20.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     172.20.30.0/24 [110/2222] via 1.2.3.5, 00:05:06, Multilink1
O E2     172.20.40.0/23 [110/2222] via 1.2.3.5, 00:05:06, Multilink1

R7#sh ip route | beg Gateway
Gateway of last resort is not set
      1.0.0.0/24 is subnetted, 1 subnets
R        1.2.3.0 [120/4] via 10.20.3.1, 00:00:28, Serial0/1
      10.0.0.0/8 is variably subnetted, 14 subnets, 2 masks
R        10.1.1.0/24 [120/4] via 10.20.3.1, 00:00:28, Serial0/1
R        10.1.2.0/24 [120/4] via 10.20.3.1, 00:00:28, Serial0/1
R        10.1.6.0/24 [120/3] via 10.20.3.1, 00:00:28, Serial0/1
R        10.10.1.0/24 [120/4] via 10.20.3.1, 00:00:28, Serial0/1
R        10.20.1.0/24 [120/2] via 10.20.3.1, 00:00:28, Serial0/1
R        10.20.2.0/24 [120/1] via 10.20.3.1, 00:00:28, Serial0/1
C        10.20.3.0/24 is directly connected, Serial0/1
L        10.20.3.2/32 is directly connected, Serial0/1
R        10.25.1.0/24 [120/3] via 10.20.3.1, 00:00:28, Serial0/1
R        10.30.1.0/24 [120/3] via 10.20.3.1, 00:00:28, Serial0/1
R        10.31.1.0/24 [120/3] via 10.20.3.1, 00:00:28, Serial0/1
R        10.35.1.0/24 [120/2] via 10.20.3.1, 00:00:28, Serial0/1
C        10.60.1.0/24 is directly connected, Loopback0
L        10.60.1.1/32 is directly connected, Loopback0
      172.20.0.0/16 is variably subnetted, 3 subnets, 2 masks
R        172.20.20.0/24 [120/3] via 10.20.3.1, 00:00:28, Serial0/1
R        172.20.30.0/24 [120/3] via 10.20.3.1, 00:00:28, Serial0/1
R        172.20.40.0/23 [120/3] via 10.20.3.1, 00:00:28, Serial0/1

R10#sh ip route | beg Gate
Gateway of last resort is not set
      1.0.0.0/24 is subnetted, 1 subnets
D EX     1.2.3.0 [170/2937856] via 10.31.1.1, 00:07:16, Serial1/0
      10.0.0.0/8 is variably subnetted, 13 subnets, 2 masks
D EX     10.1.1.0/24 [170/2937856] via 10.31.1.1, 00:07:16, Serial1/0
D EX     10.1.2.0/24 [170/2937856] via 10.31.1.1, 00:07:16, Serial1/0
D        10.1.6.0/24 [90/3193856] via 10.31.1.1, 00:32:34, Serial1/0
D EX     10.10.1.0/24 [170/2937856] via 10.31.1.1, 00:07:16, Serial1/0
D        10.20.1.0/24 [90/3193856] via 10.31.1.1, 01:07:04, Serial1/0
D        10.20.2.0/24 [90/3705856] via 10.31.1.1, 01:07:04, Serial1/0
D EX     10.20.3.0/24 [170/2937856] via 10.31.1.1, 00:54:08, Serial1/0
D        10.25.1.0/24 [90/2681856] via 10.31.1.1, 01:07:04, Serial1/0
D        10.30.1.0/24 [90/2681856] via 10.31.1.1, 01:07:04, Serial1/0
C        10.31.1.0/24 is directly connected, Serial1/0
L        10.31.1.2/32 is directly connected, Serial1/0
D        10.35.1.0/24 [90/41536000] via 10.31.1.1, 01:07:04, Serial1/0
D EX     10.60.1.0/24 [170/2937856] via 10.31.1.1, 00:53:49, Serial1/0
      172.20.0.0/16 is variably subnetted, 9 subnets, 3 masks
C        172.20.20.0/24 is directly connected, Loopback0
L        172.20.20.1/32 is directly connected, Loopback0
C        172.20.30.0/24 is directly connected, Loopback1
L        172.20.30.1/32 is directly connected, Loopback1
D        172.20.40.0/23 is a summary, 01:07:08, Null0
C        172.20.40.0/24 is directly connected, Loopback2
L        172.20.40.1/32 is directly connected, Loopback2
C        172.20.41.0/24 is directly connected, Loopback3
L        172.20.41.1/32 is directly connected, Loopback3

We have avoided routing loops in this scenario, but if the topology was the other way around, with EIGRP on the left hand side, and OSPF on the other, we would have had a routing loop on R4 and R5 into the OSPF domain. Thankfully this was not the case.

Now we can move on to Part 7 and set up a tunnel.