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OSPF neighbor not detected, Cisco Packet Tracer

Hello everyone!

Im trying to configure a simple example of OSPF between three routers (R1, R2, R3),

which are interconnected via serial ports, using DCE cables.

Each router is connected to a switch via an Ethernet port.

Each switch has PCs attached to it.

Im using Cisco Packet Tracer.

R1 serial 1/0 interface is connected to R2 serial 1/0, using a network 192.168.10.0/30.

R1 serial 1/1 interface is connected to R3 serial 1/0, using a network 192.168.10.6/30.

R2 serial 1/1 interface is connected to R3 serial 1/1, using a network 192.168.10.8/30.

R1 fa 0/0 interface is connected to switch S1 using 172.16.1.16/28 network, and in the

meantime I configured this router as a DHCP server (with the network 172.16.1.16/28)

and the router fa 0/0 as a default gateway with IP address 172.16.1.17/28.

R2 fa 0/0 interface is connected to switch S2 using 10.10.10.0/24 network, and similarly,

it is configured as a DHCP server with a default gateway 10.10.10.1/24 (fa0/0 IP).

R3 fa 0/0 interface is connected to switch S3 using 172.16.1.32/29 network, and again,

it is configured as a DHCP server with default gateway 172.16.1.33 (fa 0/0 IP).

The clock rate is configured for R1 interfaces se 1/0 and 1/1 (I tried 64000 and

other values).

When I try the show ip ospf neighbor command on each of the routers,

R2 and R3 can see each other, however they do not recognize R1 as a neighbor.

Also, R1 cannot see any neighbor at all...

First I tried to check if the OSPF is set up correctly at each router (the loopback

interfaces, router IDs, netwok connection types).

R2's serial interface can ping R1's directly connected serial interface. But it cannot ping

any other interface of R1.

Similarly, R3's serial interface can ping only R1's directly connected serial interface.

But R2 and R3 can ping each other's any interface (serial, fa).

When I try to ping a PC connected to R1 from any device that is connected to the R2 or

R3 fa interfaces, I get "Destination host unreachable."

I checked the default gateway of R1, checked that the fa 0/0 of R1 and the DHCP are

configured properly.

What could it be? Am I missing something here with respect to the OSPF configurations?

But if it was the case, why other routers see each other?

It seems that the problem comes from R1, whose serial interfaces are the ones who set up

the clock rate. Could the clock rate be the reason?

Ping 224.0.0.5 from any of the routers does not show anything.

Tracert works only for the routers R2 and R3 (from R1 I cannot see any routes)

For example when I make traceroute from R2 to a serial interface of R2, it works:

R2#traceroute 192.168.10.6
Type escape sequence to abort.

Tracing the route to 192.168.10.6

1   192.168.10.10   5 msec    5 msec    6 msec

Also, the ping and traceroute from R1's se 1/1 to R2's se 1/0 for example works too:

R1#ping 192.168.10.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.10.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/8 ms

R1#traceroute 192.168.10.6
Type escape sequence to abort.
Tracing the route to 192.168.10.6

  1   192.168.10.9    7 msec    7 msec    7 msec   
  2   192.168.10.10   7 msec    5 msec    4 msec

Thanks a lot for reading all this, and thanks for any suggestions!

Anna

3 REPLIES
Purple

OSPF neighbor not detected, Cisco Packet Tracer

Hi,

Post following outputs on R1:

-sh ip ospf int s1/0

-sh ip ospf int s1/1

-sh ip protocols

-sh ip int br

-the OSPF config from sh run

On R2 and R3 :

-sh ip ospf int s1/0 

-sh ip protocols

-sh ip int br

-the OSPF config from sh run

Regards

Alain

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Hall of Fame Super Blue

Re: OSPF neighbor not detected, Cisco Packet Tracer

Hi Anna

In addition to Alain's post -

R1 serial 1/1 interface is connected to R3 serial 1/0, using a network 192.168.10.6/30.

192.168.10.6/30 is not a subnet address. The subnet address is 192.168.10.4 and the two useable IPs are 192.168.10.5 and 192.168.10.6.

This may be a typo in your post but if not can you check your addressing and the OSPF config for this specific subnet.

Jon

i have same problem but with

i have same problem but with interface vlan at left and succes without vlan at right.
the problem is router 0 know thats neighbor is router 1 and r1 know r0, but r1 didnt know r2 and r2 too.  for r4, r5, r6 success without vlan.

 

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