Ospf Neighbors
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03-22-2010 10:33 PM - edited 03-04-2019 07:53 AM
Dear All,
i couldnt get the same list in sh ip ospf neighbors
as that of in sh cdp neighbors
what could be the reason behind this
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03-22-2010 10:47 PM
Anand,
How do you expect cdp to work like ospf ?
Please post what you did/trying to achieve ?

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03-22-2010 11:04 PM
Dear All,
i couldnt get the same list in sh ip ospf neighbors
as that of in sh cdp neighbors
what could be the reason behind this
Hi,
The show ip ospf neighbors command will work where the adjency with the neighbour is formed and the interface data structure stores information from a network to which it is connected. Using this information, an Open Shortest Path First (OSPF) router builds hello packets. These hello packets are exchanged between directly-connected neighbors to learn more about each other. You can use the show ip ospf neighbor command to observe the neighbor data structure. This command displays OSPF-related neighbor information.
Router2# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.45.1 1 FULL/DR 00:00:36 10.0.0.1 Ethernet0
Above information will be shown in show ip ospf neighbor and show cdp neighbors you will come to know the details of the neighbor devices what model and all as listed in the below example.
DCMGTSW01>sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
MGTSW02 Gig 0/50 138 R S I WS-C3560G Gig 0/50
MGTSW02 Gig 0/49 126 R S I WS-C3560G Gig 0/49
Hope to Help !!
Remember to rate the helpful post
Ganesh.H
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03-23-2010 05:06 AM
In sh ip ospf database- Routers own loopback
is there nothing else in the network
& in the sh ip ospf interface the
adjacent router isnt been advertised
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03-23-2010 05:33 AM
Could you please post your "sh ip ospf neigh" output here ?
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03-23-2010 07:47 AM
ROUTER#sh ip ospf neigh
Neighbor ID Pri State Dead Time Address Interface
10.99.0.180 0 FULL/ - 00:00:38 10.99.56.14 Serial2/1/6:0
10.99.0.179 0 FULL/ - 00:00:39 10.99.56.10 Serial2/1/5:0
10.99.0.178 0 FULL/ - 00:00:33 10.99.56.6 Serial2/1/4:0
10.99.0.177 0 FULL/ - 00:00:37 10.99.56.2 Serial2/1/3:0
10.99.0.181 0 FULL/ - 00:00:35 10.99.56.18 Serial2/1/2:0
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03-23-2010 08:15 AM
Voila..we have neighbors...
sh ip os dat and sh ip os interface doesnt look meaningful enough ?
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03-23-2010 11:25 PM
but i could not get the ospf neighbors at 2/1/0:0
2/1/7:0 & 2/1/1:0 interface
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03-23-2010 11:39 PM
Hello Anandkumar,
post
sh ip ospf interface ser2/1/0:0
sh ip ospf interface ser2/1/7:0
sh ip ospf interface ser2/1/1:0
if possible take the same show on the other side of each link
This should provide information to explain why these OSPF adjacencies are not built
Among more common causes:
missing network area command covering the IP subnets on these links under router OSPF
passive-interface for these on one side under router OSPF process
an MTU mismatch
an OSPF authentication mismatch
an area id mismatch (different area number)
an area type mismatch (stub vs. normal area)
OSPF timers mismatch (this can be caused by an OSPF network type mismatch)
all these informations can be seen in sh ip ospf interface.
you can also do the following
you can shut a serial interface for example ser2/1/0:0
you can enable terminal monitor
debug ip ospf adjacency
then you re-enable the interface and you see what happens
Hope to help
Giuseppe
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03-24-2010 04:17 AM
below is the output which you have asked/ also the debug output
& the subnetnetworks advertised are the same below for all ospfRouters
ROUTER#sh ip ospf int s2/1/0:0
Serial2/1/0:0 is up, line protocol is up
Internet Address 10.99.56.25/30, Area 0
Process ID 100, Router ID 10.99.0.189, Network Type POINT_TO_POINT, Cost: 5040
Topology-MTID Cost Disabled Shutdown Topology Name
0 5040 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Hello due in 00:00:02
Index 2/2, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
ROUTER#sh ip ospf int s2/1/1:0
Serial2/1/1:0 is up, line protocol is up
Internet Address 10.99.56.21/30, Area 0
Process ID 100, Router ID 10.99.0.189, Network Type POINT_TO_POINT, Cost: 5040
Topology-MTID Cost Disabled Shutdown Topology Name
0 5040 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Hello due in 00:00:00
Index 3/3, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
ROUTER#sh ip ospf int s2/1/7:0
Serial2/1/7:0 is up, line protocol is up
Internet Address 10.99.56.65/30, Area 0
Process ID 100, Router ID 10.99.0.189, Network Type POINT_TO_POINT, Cost: 5040
Topology-MTID Cost Disabled Shutdown Topology Name
0 5040 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Hello due in 00:00:03
Index 9/9, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
000696: *Mar 24 16:20:18.089 GMT: OSPF: Rcv pkt from 10.99.56.26, Serial2/1/1:0,
area 0.0.0.0 : src not on the same network
000697: *Mar 24 16:20:19.245 GMT: OSPF: Rcv pkt from 10.99.57.14, Serial2/1/7:0,
area 0.0.0.0 : src not on the same network
000698: *Mar 24 16:20:24.749 GMT: OSPF: Rcv pkt from 10.99.56.22, Serial2/1/0:0,
area 0.0.0.0 : src not on the same network
000699: *Mar 24 16:20:28.089 GMT: OSPF: Rcv pkt from 10.99.56.26, Serial2/1/1:0,
area 0.0.0.0 : src not on the same network
000700: *Mar 24 16:20:29.245 GMT: OSPF: Rcv pkt from 10.99.57.14, Serial2/1/7:0,
area 0.0.0.0 : src not on the same network
000701: *Mar 24 16:20:34.753 GMT: OSPF: Rcv pkt from 10.99.56.22, Serial2/1/0:0,
area 0.0.0.0 : src not on the same network
000702: *Mar 24 16:20:38.089 GMT: OSPF: Rcv pkt from 10.99.56.26, Serial2/1/1:0,
area 0.0.0.0 : src not on the same network
000703: *Mar 24 16:20:39.245 GMT: OSPF: Rcv pkt from 10.99.57.14, Serial2/1/7:0,
area 0.0.0.0 : src not on the same network
000704: *Mar 24 16:20:44.753 GMT: OSPF: Rcv pkt from 10.99.56.22, Serial2/1/0:0,
area 0.0.0.0 : src not on the same network
000705: *Mar 24 16:20:48.089 GMT: OSPF: Rcv pkt from 10.99.56.26, Serial2/1/1:0,
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03-24-2010 04:30 AM
Hello Anandkumar,
>> src not on the same network
check the IP subnet you have configured on both sides, I didn't list but the two OSPF neighbors need to be in the same IP subnet
you can check the ip address on the other side with
sh cdp n s2/1/0:0 det
sh cdp n s2/1/1:0 det
sh cdp n s2/1/7:0 det
for example for s2/1/0:0 the only valid ip address for the neighbor is 10.99.56.26 given the /30 mask
Hope to help
Giuseppe
