OSPF troubleshooting

[almas1989]

Hello, Good Day

I'm new to learning OSPF and made a simple lab in packet tracer and im facing an issue i have two switches connected with core by ospf point to point links 1 switch is connected and i can see it as neighbor but 2nd switch i cant see in ospf neighbor.

below is configuration from all 3 switches

switch 1

interface GigabitEthernet1/1/1

no switchport

ip flow egress

ip flow ingress

ip address 10.105.255.2 255.255.255.252

ip ospf network point-to-point

ip ospf hello-interval 5

ip ospf dead-interval 20

ip ospf priority 1

router ospf 911

router-id 10.252.5.11

log-adjacency-changes

redistribute connected subnets

passive-interface default

no passive-interface GigabitEthernet1/1/1

no passive-interface Vlan85

network 10.105.255.2 0.0.0.0 area 5

switch 2 (this switch is not becoming neighbor with switch 3)

interface GigabitEthernet1/1/1

no switchport

ip flow egress

ip flow ingress

ip address 10.105.255.3 255.255.255.248

ip ospf network point-to-point

ip ospf hello-interval 5

ip ospf dead-interval 20

ip ospf priority 1

router ospf 911

router-id 10.252.5.12

log-adjacency-changes

redistribute connected subnets

passive-interface default

no passive-interface GigabitEthernet1/1/1

network 10.105.255.10 0.0.0.0 area 5

switch 3 core

interface GigabitEthernet1/1/4

no switchport

no ip address

ip ospf network point-to-point

ip ospf hello-interval 5

ip ospf dead-interval 20

ip ospf priority 1

router ospf 911

router-id 10.252.18.0

log-adjacency-changes

redistribute connected subnets

passive-interface default

no passive-interface GigabitEthernet1/1/1

no passive-interface GigabitEthernet1/1/2

no passive-interface GigabitEthernet1/1/3

no passive-interface GigabitEthernet1/1/4

network 10.105.255.0 0.0.0.3 area 5

network 10.117.255.0 0.0.0.3 area 17

network 10.118.255.0 0.0.0.3 area 18

any help would be appreciated thanks in advance.

[Giuseppe Larosa · Accepted solution]

Hello @almas1989 ,

there is a subnet mask mismatch

switch 1

interface GigabitEthernet1/1/1

ip address 10.105.255.2 255.255.255.252




switch2:

ip address 10.105.255.3 255.255.255.248

fix it or both use the /30 or both use /29 subnet mask

Hope to help

Giuseppe

[David Ruess]

Hello,

Maybe I missed it but R3 doesn't have any IP addresses. If you're trying to form a neighborship you need an IP address on an interface in the same subnet to accomplish this.

[Joseph W. Doherty]

As a side question, why are you redistributing connected subnets?

[almas1989]

Hello,

Thanks for helping me out, issue resolved after adding

10.105.255.5 255.255.255.252 on switch 2 and 101.05.255.6 255.255.255.252 on switch 3/core