Loading ...By adjusting the hello/dead timers you can make non-compatible OSPF network types appear as neighbors via the “show ip ospf neighbor” but they won’t become “adjacent” with each other. OSPF network types that use a DR (broadcast and non-broadcast) can neighbor with each other and function properly. Likewise OSPF network types (point-to-point and point-to-multipoint) that do not use a DR can neighbor with each other and function properly. But if you mix DR types with non-DR types they will not function properly (i.e. not fully adjacent). You should see in the OSPF database “Adv Router is not-reachable” messages when you’ve mixed DR and non-DR types.
Here is what will work:
Broadcast to Broadcast
Non-Broadcast to Non-Broadcast
Point-to-Point to Point-to-Point
Point-to-Multipoint to Point-to-Multipoint
Broadcast to Non-Broadcast (adjust hello/dead timers)
Point-to-Point to Point-to-Multipoint (adjust hello/dead timers)
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thax again more greese to yuor elbow
thanks for the information. No body given this deeply idea.
Dear sirs,
thank you so much for your explanation. I’ve tried to do something after reading your article here, and what I did is the following:
3 routers.
(R3) —- (R1) —- (R5)
They all are running over frame relay interfaces. RouterB is configured with the following configuration:
interface Serial1/0
ip address 192.168.0.1 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
serial restart-delay 0
frame-relay map ip 192.168.0.3 103 broadcast
frame-relay map ip 192.168.0.4 104 broadcast
no frame-relay inverse-arp
end
RouterA is configuring like this:
interface Serial1/0
ip address 192.168.0.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-point
ip ospf hello-interval 30
serial restart-delay 0
frame-relay map ip 192.168.0.1 301 broadcast
no frame-relay inverse-arp
end
And the most interesting part – RouterC:
interface Serial1/0.1 point-to-point
ip address 192.168.0.5 255.255.255.0
ip ospf network broadcast
ip ospf hello-interval 30
ip ospf priority 200
frame-relay interface-dlci 501
end
RouterA and RouterB has formed successful adjacency and update their links as well.
Now, RouterB has formed adjacency with router C (even if they are in different network types) but no routes are installed into the database.
RouterC considers itself as DR (because it’s configured with prio 200 and it’s running broadcast network mode) while RouterB is just a p2p neighbor with FULL/- ospf neighbor state.
RouterC database shows the following:
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
192.168.0.5 192.168.0.5 737 0×80000001 0×008CF7
R5#show ip ospf database network
OSPF Router with ID (192.168.0.5) (Process ID 1)
Net Link States (Area 0)
Routing Bit Set on this LSA
LS age: 748
Options: (No TOS-capability, DC)
LS Type: Network Links
Link State ID: 192.168.0.5 (address of Designated Router)
Advertising Router: 192.168.0.5
LS Seq Number: 80000001
Checksum: 0×8CF7
Length: 32
Network Mask: /24
Attached Router: 192.168.0.5
Attached Router: 192.168.0.1
So the link in LSA2 confirms that router is running in DR mode on that link, so I’m thinking it’s normal to accept routes from R1 and at least install them in the routing table. But not:
R5#show ip ospf database router 192.168.0.1
OSPF Router with ID (192.168.0.5) (Process ID 1)
Router Link States (Area 0)
Adv Router is not-reachable <——————————– where is not reachable ? The ping confirms that there is a reachability between them
LS age: 1069
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 192.168.0.1
Advertising Router: 192.168.0.1
LS Seq Number: 80000028
Checksum: 0×1D28
Length: 84
Number of Links: 5
[CUT]
Can you, please help me to understand what is actually happen?
One more thing. What does “Routing Bit Set on this LSA ” actually means, and where we should see it?
Thank you so much in advance!
Brian!
Spot on explanation! U rock! Thanks!