How can I create a routing loop? It's not working the way I expected...
Greetings, EE.
I'm practicing some routing techniques related to the Implementing Cisco IP Routing class and exam. I'm trying to manufacture a routing loop in order to correct it with route maps and prefix lists, etc. I can't seem to get the routing loop to appear the way I thought it would, and I would like a hand.
Please consider the following topology (linked from Photobucket):
http://i107.photobucket.com/albums/m310/ivaarsen/topolgy.jpg
The lab is intended to feature mutual redistribution at two points, creating a routing loop. When I redistribute EIGRP into OSPF at R1, for example, R2 gets the routes expected in it's routing table. R2's next hop is R1 to reach the 192.168.253/254.0 networks (this is expected for now). When I try to redistribute EIGRP into OSPF at R2 there seems to be no effect. R1 maintains its routing table - it's as if the redistribution commands at R2 never happened. If I redistribute in the opposite order (R2 before R1) I have the opposite scenario.
Can someone please tell me what I'm doing wrong? I have the lab sitting in front of me, so I'll be happy to provide any other details required.
Thanks for your time.
Eric
I'm practicing some routing techniques related to the Implementing Cisco IP Routing class and exam. I'm trying to manufacture a routing loop in order to correct it with route maps and prefix lists, etc. I can't seem to get the routing loop to appear the way I thought it would, and I would like a hand.
Please consider the following topology (linked from Photobucket):
http://i107.photobucket.com/albums/m310/ivaarsen/topolgy.jpg
The lab is intended to feature mutual redistribution at two points, creating a routing loop. When I redistribute EIGRP into OSPF at R1, for example, R2 gets the routes expected in it's routing table. R2's next hop is R1 to reach the 192.168.253/254.0 networks (this is expected for now). When I try to redistribute EIGRP into OSPF at R2 there seems to be no effect. R1 maintains its routing table - it's as if the redistribution commands at R2 never happened. If I redistribute in the opposite order (R2 before R1) I have the opposite scenario.
Can someone please tell me what I'm doing wrong? I have the lab sitting in front of me, so I'll be happy to provide any other details required.
Thanks for your time.
Eric
Ken Boone
Well I know when you redistribute into eigrp, if you don't provide the metric i.e. bandwidth, mtu, reliability etc then it will not redistribute. I am not sure if the same applies in the opposite direction.
ASKER
Yes. I'm executing the same redistribute eigrp <AS> metric <metrics> command on both R1 and R2. It works on one router but doesn't on the other. Not sure what's going on.
Sometimes you need to clear the routing table to get things going
The command is something like:
clear ip eigrp neighbor ...
clear ip ospf neighbor ...
something like that - to reestablish the the peering.
Also is the iOS the same on both routers?
The command is something like:
clear ip eigrp neighbor ...
clear ip ospf neighbor ...
something like that - to reestablish the the peering.
Also is the iOS the same on both routers?
Try this ...
On R1 and R2, perform mutual redistribution (believe you've done these already) - config below
router ospf x
redis eigrp y subnets
router eigrp y
redis ospf x metric 1 1 255 1 1
On R3 - Remove those two networks from the eigrp process only the two uplinks should be in there - full config below
router eigrp y
no auto
network 192.168.1.0 0.0.0.255
network 192.168.2.0 0.0.0.255
no network 192.168.253.0 0.0.0.255
no network 192.168.254.0 0.0.0.255
redis connected metric 1 1 255 1 1
do a " clear ip ro *" on all RT's prior to verification
On R1 and R2, perform mutual redistribution (believe you've done these already) - config below
router ospf x
redis eigrp y subnets
router eigrp y
redis ospf x metric 1 1 255 1 1
On R3 - Remove those two networks from the eigrp process only the two uplinks should be in there - full config below
router eigrp y
no auto
network 192.168.1.0 0.0.0.255
network 192.168.2.0 0.0.0.255
no network 192.168.253.0 0.0.0.255
no network 192.168.254.0 0.0.0.255
redis connected metric 1 1 255 1 1
do a " clear ip ro *" on all RT's prior to verification
ASKER
kenboonejr:
No, they're not the same. In my lab:
R1: 12.2(8)T5
R2: 12.4(1c)
Running these commands makes the expected routes move from one routing table to another. For example, if I run clear ip eigrp <AS> neighbor on R1, it gets the routes I expected in its routing table (if it didn't previously have them). R1 loses them if I run this command on R2. The exact opposite happens if I run clear ip ospf <#> processes.
nazsky:
Your example config for R3 closely matches mine. I didn't have metrics specified in my redistribute command, but adding them has no effect.
No, they're not the same. In my lab:
R1: 12.2(8)T5
R2: 12.4(1c)
Running these commands makes the expected routes move from one routing table to another. For example, if I run clear ip eigrp <AS> neighbor on R1, it gets the routes I expected in its routing table (if it didn't previously have them). R1 loses them if I run this command on R2. The exact opposite happens if I run clear ip ospf <#> processes.
nazsky:
Your example config for R3 closely matches mine. I didn't have metrics specified in my redistribute command, but adding them has no effect.
ASKER
I have a similar topic in Cisco's forums. I've just shared my configs and routing tables there so I may as well here. They are as follows:
R1 config:
R1 config:
version 12.2
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname ro1
!
!
ip subnet-zero
!
!
no ip domain-lookup
!
!
!
!
interface FastEthernet0/0
ip address 10.2.7.1 255.255.255.0
duplex auto
speed auto
!
interface Serial0/0
ip address 192.168.2.1 255.255.255.0
no fair-queue
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial0/1
ip address 10.3.7.1 255.255.255.0
!
router eigrp 5
redistribute ospf 1 metric 1 1 255 1 300
network 10.3.7.0 0.0.0.255
network 192.168.2.0
no auto-summary
eigrp log-neighbor-changes
!
router ospf 1
router-id 1.1.1.1
log-adjacency-changes
redistribute eigrp 5 subnets
network 10.2.7.0 0.0.0.255 area 0
!
ip classless
ip http server
ip pim bidir-enable
!
!
alias exec blank copy flash:blank-config.txt start
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
!
endGateway of last resort is not set
10.0.0.0/24 is subnetted, 2 subnets
C 10.3.7.0 is directly connected, Serial0/1
C 10.2.7.0 is directly connected, FastEthernet0/0
O E2 192.168.254.0/24 [110/20] via 10.2.7.2, 00:07:54, FastEthernet0/0
D 192.168.1.0/24 [90/2681856] via 192.168.2.2, 00:12:33, Serial0/0
O E2 192.168.253.0/24 [110/20] via 10.2.7.2, 00:07:54, FastEthernet0/0
C 192.168.2.0/24 is directly connected, Serial0/0version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ro2
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
ip subnet-zero
!
!
ip cef
no ip domain lookup
no ip dhcp use vrf connected
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
ip address 10.2.7.2 255.255.255.0
duplex auto
speed auto
!
<output omitted>
!
interface FastEthernet2/0
no ip address
shutdown
duplex auto
speed auto
!
interface Serial2/0
ip address 10.3.7.2 255.255.255.0
!
interface Serial3/0
ip address 192.168.1.1 255.255.255.0
!
interface Serial3/1
no ip address
shutdown
no dce-terminal-timing-enable
!
interface Serial3/2
no ip address
shutdown
no dce-terminal-timing-enable
!
interface Serial3/3
no ip address
shutdown
no dce-terminal-timing-enable
!
interface Vlan1
no ip address
!
router eigrp 5
redistribute ospf 1 metric 1 1 255 1 300
network 10.3.7.0 0.0.0.255
network 192.168.1.0
no auto-summary
!
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
redistribute eigrp 5 subnets
network 10.2.7.0 0.0.0.255 area 0
!
ip http server
no ip http secure-server
!
ip classless
!
!
!
!
control-plane
!
!
!
!
alias exec blank copy flash:blank-config.txt start
alias exec frame copy flash:FrameSwitch.txt start
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
!
endGateway of last resort is not set
10.0.0.0/24 is subnetted, 2 subnets
C 10.3.7.0 is directly connected, Serial2/0
C 10.2.7.0 is directly connected, FastEthernet0/0
D EX 192.168.254.0/24 [170/2560512256] via 192.168.1.2, 00:10:20, Serial3/0
[170/2560512256] via 10.3.7.1, 00:10:20, Serial2/0
C 192.168.1.0/24 is directly connected, Serial3/0
D EX 192.168.253.0/24 [170/2560512256] via 192.168.1.2, 00:10:20, Serial3/0
[170/2560512256] via 10.3.7.1, 00:10:20, Serial2/0
D 192.168.2.0/24 [90/2681856] via 10.3.7.1, 00:14:54, Serial2/0version 12.1
no service single-slot-reload-enable
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname ro4
!
!
!
!
!
!
ip subnet-zero
no ip domain-lookup
!
!
!
!
interface Ethernet0
ip address 192.168.253.1 255.255.255.0
no keepalive
!
interface Ethernet1
ip address 192.168.254.1 255.255.255.0
no keepalive
!
interface Serial0
ip address 192.168.2.2 255.255.255.0
no fair-queue
clockrate 56000
!
interface Serial1
ip address 192.168.1.2 255.255.255.0
clockrate 56000
!
router eigrp 5
redistribute connected metric 1 1 255 1 300
network 192.168.1.0
network 192.168.2.0
no auto-summary
no eigrp log-neighbor-changes
!
ip classless
ip http server
!
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
!
endGateway of last resort is not set
10.0.0.0/24 is subnetted, 2 subnets
D 10.3.7.0 [90/2681856] via 192.168.2.1, 00:15:37, Serial0
[90/2681856] via 192.168.1.1, 00:15:37, Serial1
D EX 10.2.7.0 [170/2560512256] via 192.168.2.1, 00:15:37, Serial0
[170/2560512256] via 192.168.1.1, 00:15:37, Serial1
C 192.168.254.0/24 is directly connected, Ethernet1
C 192.168.1.0/24 is directly connected, Serial1
C 192.168.253.0/24 is directly connected, Ethernet0
C 192.168.2.0/24 is directly connected, Serial0
I can see the routing loop already - Follow routing of 253 or 254 networks from R1 you'll see you end up going in circles
Traceroute should also reveal this
Traceroute should also reveal this
ASKER
Yes, this is the point of this lab. I WANT a routing loop so I can correct it with route-maps, etc. The problem is that the redistribution command only works for the router where I first issue the command, and the second has no effect, which is the point of this question.
ASKER
I know it's strange to ask how to break something but, as I've said, the redistribution of routes from EIGRP into OSPF are not behaving as I would have expected. Do you have any insight on why this may be?
Thanks again.
Thanks again.
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ASKER
First of I want to thank you for your help. I don't mean to sound rude in my replies.
Second I apologize for the 'switcheroo' in the content of my question vs. the title. I'll reword everything and post anew.
Second I apologize for the 'switcheroo' in the content of my question vs. the title. I'll reword everything and post anew.
ASKER
Wait a second. I think I understand now.
I expected both R1 and R2 routing tables to match, but being 'mirror images'. That's not going to happen in this scenario because the 'other' router's routes were replaced with OSPF. There are no longer EIGRP networks to advertise into OSPF. The best I end up with using this topology and config is sub-optimal routing going one direction.
My problem was that of metrics. I wasn't applying all of the parts of the lab, where the distributed routes were being seeded in such a way that the routing protocols were stepping on each other, generating the loop. I tweaked my configs and I've got a mess of a loop going on now.
Thanks again for your help, I do truly appreciate it. Points go to you sir for reminding me of things I should know or remember if I'm going to be taking the exam next week.
Take it easy! -Eric
I expected both R1 and R2 routing tables to match, but being 'mirror images'. That's not going to happen in this scenario because the 'other' router's routes were replaced with OSPF. There are no longer EIGRP networks to advertise into OSPF. The best I end up with using this topology and config is sub-optimal routing going one direction.
My problem was that of metrics. I wasn't applying all of the parts of the lab, where the distributed routes were being seeded in such a way that the routing protocols were stepping on each other, generating the loop. I tweaked my configs and I've got a mess of a loop going on now.
Thanks again for your help, I do truly appreciate it. Points go to you sir for reminding me of things I should know or remember if I'm going to be taking the exam next week.
Take it easy! -Eric
Its the pleasure Eric!
I can see your having fun with the Loops :-) Great stuff!
Good Luck with your exams and Happy Studies!
Thank you
I can see your having fun with the Loops :-) Great stuff!
Good Luck with your exams and Happy Studies!
Thank you