Stub summary advertisements

Advertise summary type 3 to stub

router ospf1
area 14 stub

Advertise summary default route only

router ospf 1
area 14 stub no-summary

Gateway of last resort is 10.1.1.1 to network 0.0.0.0
172.16.0.0/26 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, Loopback99 10.0.0.0/26 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, FastEthernet0/0
O*IA 0.0.0.0/0 [110/2] via 10.1.1.1, 00:00:03, FastEthernet0/0

Stub area configuration

Gateway of last resort is 10.1.1.1 to network 0.0.0.0
172.16.0.0/26 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, Loopback99 10.0.0.0/26 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, FastEthernet0/0 192.168.1.0/26 is subnetted, 1 subnets
O IA 192.168.1.0 [110/2] via 10.1.1.1, 00:03:37, FastEthernet0/0 192.168.3.0/32 is subnetted, 1 subnets
O IA 192.168.3.1 [110/3] via 10.1.1.1, 00:03:37, FastEthernet0/0
O*IA 0.0.0.0/0 [110/2] via 10.1.1.1, 00:03:37, FastEthernet0/0

router#sh run sec router ospf
router ospf 1
log-adjacency-changes
area 14 stub
network 10.1.1.0 0.0.0.63 area 14
network 172.16.0.0 0.0.0.63 area 14

Types of area

Standard area - every router knows every prefix
Stub area - does not accept type 5 external summary routes, default is provided by ABR
Totally stubby area - does not accept type 3,4,5 summary routes, default is provided by ABR
Not So Stubby area (NSSA) - stubby areas that can have an ASBR, type 5 LSA are disguised by type 7 LSA and converted to type 5 on ABR

Types of Link State Advertisemnt

Router link type 1 - lists neighbours and cost to each, flooded within an area
Network link type 2 - send by DR, lists all routers it is adjacent to, flooded within an area
Network summary link type 3 - send by ABR, lists prefixes in area, advertises summary
AS external ASBR summary link type 4 - send by ASBR, describes external route
External Link LSA type 5 - external route advertised by ASBR, type 5 can also be default-route
NSSA external type 7 -created by ASBR in not so stubby area, type 5 tunnelled through NSSA, converted to type 5 on ABR.

OSPF Router Types

Internal router - within an area, all interfaces within same area
Backbone router - all areas are interconnected via a backbone area 0interface in area 0
Area Border Router - connects two or more areas, holds a full topological database for each area, sends summary LSA
AS boundary router - connects to other routing domains, router typically located in backbone area

NBMA Frame Relay Configuration

!
interface Serial1/0
ip address 192.168.1.1 255.255.255.0
encapsulation frame-relay
ip ospf network non-broadcast
serial restart-delay 0
frame-relay map ip 192.168.1.2 102 broadcast
frame-relay map ip 192.168.1.3 103 broadcast
no frame-relay inverse-arp
end
Router#sh run sec router ospf
router ospf 1
router-id 192.168.1.1
log-adjacency-changes
network 192.168.1.0 0.0.0.255 area 1
neighbor 192.168.1.2
neighbor 192.168.1.3

OSPF Network Types

OSPF assumes that all routers can communicate directly using multicast, and that no router is uniquely positioned. Routers on an Ethernet segment can communicate directly, however NBMA (None Broadcast Multi Access) network types are not able to.

The following are OSPF network types configurable on a Cisco interface:
- Broadcast multiaccess
- Point-to-point
- Point-to-multipoint
- None Broadcast Multiaccess (NBMA)

On NMBA networks multicast communications are simulated by sending advertisements directly to each neighbour.

Point-to-point or Ethernet networks are automatically detected