help with opsf packet tracer

shaqkori · ‎02-19-2023

Hello, ive been trying to configure a wan using multi area ospf but the neighbors do not seem to be picking up each other apart from two in area zero.

I have made sure to use the same subnet mask and they still do not pick up on each other.

thank you in advance.

David Ruess · ‎02-19-2023

Hello,

I am unable to view the PT file at this time. Can you provide a screenshot of the topology and configs of the 2 devices you are trying to establish an adjacency with?

Remember OSPF neighbors need to be in the same subnet, but also have connecting interfaces in the same area, same network type (or at least same hello/dead timers), same authentication parameters, and different RIDs. Also in multi-Area OSPF the other Areas need to connect to the backbone of Area 0.

-David

shaqkori · ‎02-19-2023

sure here is the topology

R3

Router(config)#router ospf 1

Router(config-router)#router-id 1.1.1.1

Router(config-router)#network 4.0.0.1 0.0.0.7 area 2

Router(config-router)#network 1.0.0.1 0.0.0.7 area 2

Router(config-if)#ip address 7.0.0.1 255.255.255.248

Router(config-if)#no shut

Router(config-if)#exit

Router(config)#router ospf 1

Router(config-router)#

Router(config-router)#router-id 8.8.8.8

Router(config-router)#Reload or use "clear ip ospf process" command, for this to take effect

Router(config-router)#network 8.0.0.1 0.0.0.7 area 2

Router(config-router)#network 5.0.0.1 0.0.0.7 area 2

Router(config-router)#exit

R18

Router(config)# int se0/1/1

Router(config-if)#ip address 8.0.0.1 255.255.255.248

Router(config-if)#

Router(config-if)#no shut

Router(config-if)#

Router(config-if)#exit

Router(config)#

Router(config)#router ospf 1

Router(config-router)#

Router(config-router)#router-id 5.5.5.5

Router(config-router)#network 7.0.0.1 0.0.0.7 area 2

Router(config-router)#

05:56:07: OSPF: Build router LSA for area 2, router ID 5.5.5.5, seq 0xffffffff8000000e

David Ruess · ‎02-19-2023

Looks like the main problem is youre not enabling OSPF on the interfaces. The netowrk statments must match up to the interfaces you want to participate and form adjacencies over OSPF with.

For example you sent:

R3

Router(config)#router ospf 1

Router(config-router)#router-id 1.1.1.1

Router(config-router)#network 4.0.0.1 0.0.0.7 area 2

Router(config-router)#network 1.0.0.1 0.0.0.7 area 2

Router(config-if)#ip address 7.0.0.1 255.255.255.248

Neither of those network statement include the IP address of the interface so it wont enable OSPF on it.

You would need network 7.0.0.0 0.0.0.3 area 2 to activate OSPF on the interface with the 7.0.0.1 IP address.

You would need it fix this on all devices you want to form an adjacency with for it to work

Hope that helps

-David

shaqkori · ‎02-19-2023

Thank you very much i didnt realise i had to set it up on the interfaces individually.

Joseph W. Doherty · ‎02-19-2023

"Thank you very much i didnt realise i had to set it up on the interfaces individually."

You don't, but how OSPF network statements work, can be a bit confusing, especially if you've used the network statement with some other dynamic routing protocols.

The best way I believe to understand it, is consider the OSPF network statement(s) like an ACL's ACEs matching for an IP on an interface.

For example given two interfaces with:

ip address 192.168.1.126 255.255.255.128
ip address 192.168.1.129 255.255.255.128

And I want both those interface networks in OSPF, I might:
(note, values in [] show acceptable range values, cannot use directly as shown)

network 192.168.1.126 0.0.0.0 area 10
network 192.168.1.129 0.0.0.0 area 10
or
network 192.168.1.[124..127] 0.0.0.3 area 10
network 192.168.1.[128..131] 0.0.0.3 area 10
or
network 192.168.1.[0..127] 0.0.0.127 area 10
network 192.168.1.[128..255] 0.0.0.127 area 10
or
network 192.168.1.[0..255] 0.0.0.255 area 10
or
network 192.168.[0.0..255.255] 0.0.255.255 area 10
or
network [any] 255.255.255.255 area 10

and you can overlap, like in an ACL, e.g.:

network 192.168.1.[124..127] 0.0.0.3 area 10
network 192.168.1.[0..255] 0.0.0.255 area 20
network [any] 255.255.255.255 area 30

PS:

BTW, although the above shows how OSPF network statements work, not matching prefix with its mask, I consider poor practice.

For example, if matching a /25 network, I would use, for the IP, either the exact interface IP, or the network prefix, and would not use a wildcard, other than for interface IPs, smaller than the network's.

E.g. given: ip address 192.168.1.129 255.255.255.128

I might use:

network 192.168.1.129 0.0.0.0 area 10
or
network 192.168.1.128 0.0.0.127 area 10
or
network 192.168.1.0 0.0.0.255 area 10
or
network 192.168.0.0 0.0.255.255 area 10
or
network 0.0.0.0 255.255.255.255 area 10

Joseph W. Doherty · ‎02-19-2023

Well, I haven't checked your whole topology (I was able to open your PT file), but just starting with routers 5 and 18, looking at just one link, we have (after adding hostnames to both):

router5#sh cdp n
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
Router Fas 0/0 152 R C2800 Fas 0/0
Router Ser 0/1/0 93 R C2800 Ser 0/3/1
Router Ser 0/1/1 154 R C2800 Ser 0/1/0
router18 Ser 0/1/0 153 R C2800 Ser 0/3/1

router18#sh cdp n
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
Router Fas 1/0 169 R C2800 Fas 0/0
Router Fas 0/0 170 R C2800 Fas 0/0
Router Fas 0/1 161 R C2800 Fas 0/0
Router Ser 0/3/1 108 R C2800 Ser 0/1/0
Router Ser 0/1/0 170 R C2800 Ser 0/1/1
Router Ser 0/1/1 170 R C2800 Ser 0/1/1
Router Ser 0/3/0 161 R C2800 Ser 0/1/0
router5 Ser 0/3/1 168 R C2800 Ser 0/1/0

relevant parts of configs:

interface Serial0/1/0
ip address 21.0.0.1 255.255.255.248

router ospf 1
router-id 1.1.1.1
log-adjacency-changes
network 20.0.0.0 0.0.0.7 area 0
network 22.0.0.0 0.0.0.7 area 0

interface Serial0/3/1
ip address 20.0.0.1 255.255.255.248

router ospf 1
router-id 1.1.1.1
log-adjacency-changes
network 7.0.0.0 0.0.0.7 area 2
network 11.0.0.0 0.0.0.7 area 2
network 21.0.0.0 0.0.0.7 area 0
network 29.0.0.0 0.0.0.7 area 0

See any issues? (I see several, for even getting this one link into OSPF! Review what @David Ruess posted.)

If you can get just this one link operational, you'll likely be able to also do so for all the others.

If you're still totally lost, let us know.

(BTW, with OSPF, you don't directly configure an interface's network into OSPF, you get the interface into OSPF and it will "know" the network. [Might sound to be the same thing, but it's not.] Later Cisco OSPF implementations have another way to get their interfaces into OSPF, which makes this difference "go away", i.e. it will be the former approach, implicitly.)

shaqkori · ‎02-19-2023

thank you for this as well i see where i went wrong now

Joseph W. Doherty · ‎02-19-2023

Great, and in a topology like this one, setting device's hostname to match PT's device name, can make it a lot easier to work with the devices, as you might have noticed in my usage of CDP.

Also, even more useful in the real-world where you may not have a high level diagram of the network, and you're trying to determine what the topology actually looks like (or, at least, what's other device[s] connect to an interface).