[nsp] RE: [nsp] OSPF
odusseus
odusseus@voila.fr
Fri, 11 Oct 2002 12:09:22 +0200
Hi,
Many thanks for your prompt reply. I am sending more info as I change their OSPF ID.
R1---------R2-----------R3
R1 and R2 are running OSPF between each other.
R3 belongs to another AS.
I set up their OSPF ID as follow:
R1_ID = 0.0.0.1
R2_ID = 0.0.0.2
Each router has its own loopback Ip address.
For several reasons, I do need R2 to have another loopback interface with the same IP address as the loopback interface of R1.
On R2 this second loopback interface is shuted down and configured as passive-interface.
As a result:
R3 is not able to ping the loopback interface of R1.
R2 is able to ping the loopback interface of R1.
>From R3 I run this two debug commands:
debug IP packet detail
debug arp
...and then from R3 I ping the loopback Ip address of R1 (10.10.10.3).
>From the following log it appears that R3 (192.168.100.1) sends a ARP request and gets the correct answer.
The MAC address that R3 gets is corresponding to the MAC address of R1's ethernet interface (0060.474f.88f1).
-----
R3>ping 10.10.10.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.3, timeout is 2 seconds:
2d16h: IP: s=192.168.100.1 (local), d=10.10.10.3 (FastEthernet0), len 100, sending
2d16h: ICMP type=8, code=0.
2d16h: IP: s=192.168.100.1 (local), d=10.10.10.3 (FastEthernet0), len 100, sending
2d16h: ICMP type=8, code=0.
2d16h: IP: s=192.168.100.1 (local), d=10.10.10.3 (FastEthernet0), len 100, sending
2d16h: ICMP type=8, code=0
2d16h: IP ARP: creating incomplete entry for IP address: 10.10.10.3 interface FastEthernet0
2d16h: IP ARP: sent req src 192.168.100.1 0007.5049.aca2,
dst 10.10.10.3 0000.0000.0000 FastEthernet0
2d16h: IP ARP: sent req src 192.168.100.1 0007.5049.aca2,
dst 10.10.10.3 0000.0000.0000 FastEthernet0
2d16h: IP ARP: rcvd rep src 10.10.10.3 0060.474f.88f1, dst 192.168.100.1 FastEthernet0
2d16h: IP ARP: rcvd rep src 10.10.10.3 0060.474f.88f1, dst 192.168.100.1 FastEthernet0.
2d16h: IP: s=192.168.100.1 (local), d=10.10.10.3 (FastEthernet0), len 100, sending
2d16h: ICMP type=8, code=0.
2d16h: IP: s=192.168.100.1 (local), d=10.10.10.3 (FastEthernet0), len 100, sending
2d16h: ICMP type=8, code=0.
Success rate is 0 percent (0/5)
R3>
-----
Then, from R3 (192.168.100.1) I do a traceroute to 10.10.10.3 (loopback address of R1), R3 asks the MAC address of 10.10.10.3 and gets the correct answer but the traceroute failed after it reaches the Ethernet IP address of R1 (10.100.100.1):
---
R3#traceroute 10.10.10.3
Type escape sequence to abort.
Tracing the route to 10.10.10.3
1 10.100.100.1 4 msec 4 msec *
R3#
---
This is the log on R3 during the previous traceroute:
-----
2d16h: IP: s=192.168.200.1 (Loopback0), d=255.255.255.255, len 71, unroutable
2d16h: UDP src=58759, dst=53
2d16h: IP ARP: creating incomplete entry for IP address: 10.10.10.3 interface FastEthernet0
2d16h: IP ARP: sent req src 192.168.100.1 0007.5049.aca2,
dst 10.10.10.3 0000.0000.0000 FastEthernet0
2d16h: IP ARP: sent req src 192.168.100.1 0007.5049.aca2,
dst 10.10.10.3 0000.0000.0000 FastEthernet0
2d16h: IP ARP: rcvd rep src 10.10.10.3 0060.474f.88f1, dst 192.168.100.1 FastEthernet0
2d16h: IP ARP: rcvd rep src 10.10.10.3 0060.474f.88f1, dst 192.168.100.1 FastEthernet0
2d16h: IP: s=192.168.100.1 (local), d=255.255.255.255 (FastEthernet0), len 71, sending broad/multicast
2d16h: UDP src=58759, dst=53
2d16h: IP: s=192.168.200.1 (local), d=255.255.255.255 (Loopback0), len 71, sending broad/multicast
2d16h: UDP src=58759, dst=53
2d16h: IP: s=192.168.200.1 (Loopback0), d=255.255.255.255, len 71, unroutable
2d16h: UDP src=58759, dst=53
-----
So I conclude that even with the correct MAC address R3 is not able to reach R1's loopack IP address because of R2.
OSPF seems to be responsable of this because if OSPF is not running, then R3 can reach R1's loopack IP address.
I don't understand why this is happening!
Following is a "sho ip ospf data router" done on R2:
0.0.0.1 = OSPF ID of R1
10.10.10.3 = lo 0 of R1
10.100.100.1 = eth 0 of R1
0.0.0.2 = OSPF ID of R2
10.10.10.2 = lo 0 of R2
10.100.100.2 = eth 0 of R2
*****************
R2#sh ip ospf da ro
OSPF Router with ID (0.0.0.2) (Process ID 1)
Router Link States (Area 0)
LS age: 220
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 0.0.0.1
Advertising Router: 0.0.0.1
LS Seq Number: 80000003
Checksum: 0xAE9C
Length: 48
Number of Links: 2
Link connected to: a Stub Network
(Link ID) Network/subnet number: 10.10.10.3
(Link Data) Network Mask: 255.255.255.255
Number of TOS metrics: 0
TOS 0 Metrics: 1
Link connected to: a Transit Network
(Link ID) Designated Router address: 10.100.100.2
(Link Data) Router Interface address: 10.100.100.1
Number of TOS metrics: 0
TOS 0 Metrics: 10
LS age: 178
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 0.0.0.2
Advertising Router: 0.0.0.2
LS Seq Number: 80000003
Checksum: 0xB492
Length: 48
AS Boundary Router
Number of Links: 2
Link connected to: a Stub Network
(Link ID) Network/subnet number: 10.10.10.2
(Link Data) Network Mask: 255.255.255.255
Number of TOS metrics: 0
TOS 0 Metrics: 1
Link connected to: a Transit Network
(Link ID) Designated Router address: 10.100.100.2
(Link Data) Router Interface address: 10.100.100.2
Number of TOS metrics: 0
TOS 0 Metrics: 10
R2#
*****************
Thank you very much.
Regards,
Christophe
> Hi,
>
> I am making some experiments and I have a problem when OSPF is running.
>
> This is the net topology where R3 is never running any routing protocol.
>
> Router1----Router2----Router3
>
> R1 has a loopback IP address pingable from R2 and R3.
>
> I set up an loopback interface on R2 whith the same IP address as R1, but I keep the loopback interface of R2 shuted down.
>
> Now if OSPF is not running between R1 and R2, R3 can ping R1 loopback interface.
>
> But if OSPF is running between R1 and R2, then R3 cannot ping R1 loopback interface. (although I set it up as passive-interface.) Why?
>
> If someone has an idea to share with me, he is more than welcome.
>
> Thank you.
>
> Regards,
>
> Christophe
>
> ------------------------------------------
>
> Faites un voeu et puis Voila ! www.voila.fr
>
> _______________________________________________
> cisco-nsp mailing list real_name)s@puck.nether.net
> http://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
------------------------------------------
Faites un voeu et puis Voila ! www.voila.fr