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1. Re: Two default routes...
Conwyn Aug 12, 2010 9:39 AM (in response to Deepak)Hi Deepak
Are you using ping 1.2.3.4 source interface-name?
Regards Conwyn
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2. Re: Two default routes...
Wendell Odom Aug 12, 2010 10:02 AM (in response to Deepak)Deepak,
I agree with Conwyn about the source interface, since R1 or R3 will need to route with which to send back the Echo Reply.
Another thing to check: if you have <no ip classless> configured on R2. If so, change it to <ip classless> and try it again. That may do the trick.
Regards,
Wendell
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3. Re: Two default routes...
Claudius Aug 12, 2010 10:15 AM (in response to Deepak)Hi Deepak,
If you ping from Lo1 (R1) to lo2 (R2)
It's needed that all routers on the way could handle the destination and/or source of ping packet. As I understand there's no routing configured but 2 static routes on R2. If I am correct, neither R1 nor R3 are aware of remote loopback networks, so...
How Can it ber delivered? How Can it be Delivered Back?
Unreachable Destination.
Regards,
Carlos
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4. Re: Two default routes...
Deepak Aug 12, 2010 10:48 AM (in response to Claudius)Dear all!
Thanks for your responces...
Conwyn and Wendell I've tried the stuff you suggested, but ping is still not working, Carlos, I'm not pinging from R1 to R3, Im trying pining R3/R1's loopback from R2.
Here I've tried building lab, please let me know if I misses somthing...
R1 config
-------------
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface FastEthernet0/0
ip address 10.1.1.2 255.255.255.0
duplex auto
speed auto
!ip route 0.0.0.0 0.0.0.0 FastEthernet0/0 10.1.1.1
!
Gateway of last resort is 10.1.1.1 to network 0.0.0.0
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, FastEthernet0/0
S* 0.0.0.0/0 [1/0] via 10.1.1.1, FastEthernet0/0R2 config
-------------
interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 20.1.1.2 255.255.255.0
duplex auto
speed auto
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 20.1.1.1
ip route 0.0.0.0 0.0.0.0 FastEthernet0/0 10.1.1.2
!Gateway of last resort is 20.1.1.1 to network 0.0.0.0
20.0.0.0/24 is subnetted, 1 subnets
C 20.1.1.0 is directly connected, FastEthernet0/1
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, FastEthernet0/0
S* 0.0.0.0/0 [1/0] via 20.1.1.1, FastEthernet0/1
[1/0] via 10.1.1.2, FastEthernet0/0R3 config
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interface Loopback0
ip address 3.3.3.3 255.255.255.255
!
interface FastEthernet0/1
ip address 20.1.1.1 255.255.255.0
duplex auto
speed auto
!
ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 20.1.1.2!
Gateway of last resort is 20.1.1.2 to network 0.0.0.0
3.0.0.0/32 is subnetted, 1 subnets
C 3.3.3.3 is directly connected, Loopback0
20.0.0.0/24 is subnetted, 1 subnets
C 20.1.1.0 is directly connected, FastEthernet0/1
S* 0.0.0.0/0 [1/0] via 20.1.1.2, FastEthernet0/1Motive behind doing this is, I'm trying to find out...will this work IF YES then how? and IF NOT then how?
Thanks
Deepak
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topology.jpg 13.1 K
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5. Re: Two default routes...
Sonu Khandelwal Aug 12, 2010 11:05 AM (in response to Deepak)Hi Deepak,
Lets say You want to ping 3.3.3.3 from R2. R2 wont have any way to know if packet should be send to R1 or R3 becuase it has both the routes in its table. Lets say if it sent to R3 and its doing per prefix loadbalancing then your ping will succeed.
If R2 is doing per packet load balancing then alternate ping packets will succeed.
Experts can correct me, If I am wrong here.
Thanks,
Sonu
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6. Re: Two default routes...
Chad Spears CCNP CCDA CCNAS Aug 12, 2010 11:15 AM (in response to Sonu Khandelwal)Deepak-
I agree with Sonu; it appears that you should have the following on R2:
ip route 1.1.1.1 (*Subnet Mask*) FastEthernet 0/0
ip route 3.3.3.3 (*Subnet Mask*) FastEthernet 0/1
This should work....As always Experts let me know if I am wrong.
Thanks,
CS
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7. Re: Two default routes...
Chad Spears CCNP CCDA CCNAS Aug 12, 2010 11:18 AM (in response to Chad Spears CCNP CCDA CCNAS)nevermind I just read the title of the post. .....Oops!
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8. Re: Two default routes...
DelVonte Aug 12, 2010 11:33 AM (in response to Deepak)I don't think you can have two static default routes, how will R2 know which one to use. Also, in order to be able to ping the loopback interfaces, you will have to provide a route to those interfaces.
I wasn't really sure how configuring two default routes would work, so I put it together in Packet Tracer:
R2#ping 3.3.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
..!.!
Success rate is 40 percent (2/5), round-trip min/avg/max = 3/3/3 msR2#ping 3.3.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
.!.!.
Success rate is 40 percent (2/5), round-trip min/avg/max = 4/4/5 msR2#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
.!.!.
Success rate is 40 percent (2/5), round-trip min/avg/max = 3/4/5 msR2#
I was really surprised that I got any response. Heres the output after removing one default route and configuring static routes to the loopback interfaces:
R2#
R2#
R2#config t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#no ip route 0.0.0.0 0.0.0.0 20.1.1.2
R2(config)#ip route 1.1.1.1 255.255.255.255 10.1.1.2
R2(config)#ip route 3.3.3.3 255.255.255.255 20.1.1.2
R2(config)#^Z
R2#
%SYS-5-CONFIG_I: Configured from console by consoleR2#ping 3.3.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/3/6 msR2#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 3/4/6 msR2#
HTH
DelVonte
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9. Re: Two default routes...
Claudius Aug 12, 2010 11:54 AM (in response to Deepak)Hi Deepak,
I see, I misunderstood the question, but there's not only 2 default routes, actually they're all over the place... Interesting scenario.
I belive that the point in this case is how packets will be processed, try to disable ip cef, that would work.
Let me know if I am on the way .
Regards,
Carlos.
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10. Re: Two default routes...
Wendell Odom Aug 12, 2010 11:55 AM (in response to DelVonte)Deepak and DelVonte,
Actually, the results DelVonte sees with the defaults is what I would have expected. You can have multiple default routes in the routing table at the same time, but I agree it's not useful for real life. Deepak, I'm sure you mention somewhere that you're just testing to see what happens.
Backing up a step, Deepak... any chance the cabling differs from your figure? EG, R2's Fa0/1 is actually cabled to R1's Fa0/0? That would fit the symptoms at least. One other thought: I've not used the syntax "ip route 0.0.0.0 0.0.0.0 fa0/0 10.1.1.2" often, instead just listing the next-hop IP address (ip route 0.0.0.0 0.0.0.0 10.1.1.2) in such cases. May be worth a shot. Last suggestion, and I'll stop: shut down one LAN interface on R2, and see if you can at least ping the router that's still possibly reachable, and get that working before adding back the other side.
That's all I can think to try. I'll be curious to see your results.
Thanks,
Wendell
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11. Re: Two default routes...
DelVonte Aug 12, 2010 11:56 AM (in response to Claudius)I'm not really sure if any of us know exactly what is being asked
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12. Re: Two default routes...
Deepak Aug 12, 2010 12:23 PM (in response to DelVonte)Thanks for replies friends.
@CS: I'll never
@DelVonte, I wanted to use static DEFAULT routes to check how packets are sent or received, you are using static routes in your scenario. I've built this topology on GNS3, my results are different, I've not received any echo reply (100% loss), while using two static Default routes, maybe PT is acting in your case.
@Wandell..I'm just testing it. I'm very much correct with my posted topology, and sure enough if I shutdown one interface I can ping other side.
@Sonu, your suggestion worked..but I get a 100% ping success while using either of the method (per packet or destination), as you said per packet should return alternate pings (means say 40% success), any clue why and how this happened?@Carlos...Your suggestion, disabling cef also worked and yes "I belive that the point in this case is how packets will be processed" you are correct here I'm trying to find exactly what you have mentioned.
What I concluded is:- While having two default routes in two different direction then router will not be able to pass traffic, eventhough both the default routes exist in routing table, because of it is not able to take decision which route to use.
Please let me know IF I'm right or if you would like to add any findings with my conclusion Considering above mentioned topology, and configs OR will it happen in any case?Thanks,
Deepak
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13. Re: Two default routes...
Conwyn Aug 12, 2010 12:53 PM (in response to Deepak)Hi Deepak
You might find this interesting especially Toor's post.
See https://learningnetwork.cisco.com/message/39389#39389
Regards Conwyn
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14. Re: Two default routes...
DelVonte Aug 12, 2010 1:43 PM (in response to Conwyn)That is interesting and enlightening, I never thought about it from that perspective. Always assumed just one default route, now I have to play around with this. Thanks for the post Deepak, and thanks for the link Conwyn. I learn quite a bit on CLN everyday.
Regards
DelVonte