BROADCAST
Ethernet = broadcast (default)
broadcast:
- DR/BDR election
- multicast updates
On r1:
r1#show ip ospf interface f0/0
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.123.1/24, Area 0
Process ID 1, Router ID 192.168.123.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DROTHER, Priority 1
Designated Router (ID) 192.168.123.3, Interface address 192.168.123.3
Backup Designated router (ID) 192.168.123.2, Interface address 192.168.123.2
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:03
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 192.168.123.2 (Backup Designated Router)
Adjacent with neighbor 192.168.123.3 (Designated Router)
Suppress hello for 0 neighbor(s)
On BROADCAST, there DR/BDR election : highest router-id or lowest priority.
No preemption exist if the DR fails: if r1 start first, then r3, then r2, r1 will br dr and r3 bdr.
From the DR/BDR other routers on the segment are seen as FULL/DROTHER.
From other routers, non DR/BDR neighbors are in 2WAY state.
No preemption exist if the DR fails: if r1 start first, then r3, then r2, r1 will br dr and r3 bdr.
From the DR/BDR other routers on the segment are seen as FULL/DROTHER.
From other routers, non DR/BDR neighbors are in 2WAY state.
r1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.123.2 1 FULL/BDR 00:00:31 192.168.123.2 FastEthernet0/0
192.168.123.3 1 FULL/DR 00:00:34 192.168.123.3 FastEthernet0/0
r2#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.123.3 0 FULL/ - 00:00:38 23.0.0.3 FastEthernet0/0
192.168.123.1 1 FULL/DROTHER 00:00:38 192.168.123.1 Ethernet1/0
192.168.123.3 1 FULL/DR 00:00:39 192.168.123.3 Ethernet1/0
r3#sho ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.123.2 0 FULL/ - 00:00:38 23.0.0.2 FastEthernet1/0
192.168.123.1 1 FULL/DROTHER 00:00:38 192.168.123.1 FastEthernet0/0
192.168.123.2 1 FULL/BDR 00:00:38 192.168.123.2 FastEthernet0/0
the following routes are present on each router:
r1#show ip route ospf
23.0.0.0/24 is subnetted, 1 subnets
O 23.0.0.0 [110/2] via 192.168.123.3, 00:01:13, FastEthernet0/0
[110/2] via 192.168.123.2, 00:01:13, FastEthernet0/0
r2#show ip route ospf
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/3] via 23.0.0.3, 00:01:28, FastEthernet0/0
r3#show ip route ospf
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/2] via 192.168.123.1, 00:01:50, FastEthernet0/0
From r2, 1.1.1.1/32 is reachable via r3 and not r1 because r2 is connected via an 10bT interface to the switch:
r2#show ip ospf interface ethernet 1/0 | include Cost
Process ID 1, Router ID 192.168.123.2, Network Type BROADCAST, Cost: 10
On the other side, r1 has two routes to 23.0.0.0/24 via r3 and r2 even if r2 uses ethernet link.
To solve this problem we can change the network type to POINT_TO_MULTIPOINT
NON_BROADCAST (no DR/BDR election, manual configuration of the neighbors). This will allow the configuration of the cost on a per neighbor basis.
NON_BROADCAST (no DR/BDR election, manual configuration of the neighbors). This will allow the configuration of the cost on a per neighbor basis.
POINT_TO_POINT NON_BROADCAST
point_to_point non_broadcast:
- no DR/BDR election (point_to_point)
- unicast updates (non_broadcast)
With FR Hub&Spoke, there is no need to configure the hub as neighbor on each spoke, configuring the hub was sufficient. With Ethernet, it is highly recommanded.
On r1:
!
router ospf 1
router ospf 1
router-id 192.168.123.1
log-adjacency-changes
passive-interface Loopback0
network 1.1.1.1 0.0.0.0 area 0
network 192.168.123.1 0.0.0.0 area 0
neighbor 192.168.123.3 cost 1
neighbor 192.168.123.2 cost 10
!
interface FastEthernet0/0
ip address 192.168.123.1 255.255.255.0
ip ospf network point-to-multipoint non-broadcast
duplex auto
speed auto
!
r1#show ip route ospf
192.168.123.0/24 is variably subnetted, 3 subnets, 2 masks
O 192.168.123.3/32 [110/1] via 192.168.123.3, 00:29:03, FastEthernet0/0
O 192.168.123.2/32 [110/2] via 192.168.123.3, 00:29:03, FastEthernet0/0
23.0.0.0/24 is subnetted, 1 subnets
O 23.0.0.0 [110/2] via 192.168.123.3, 00:29:03, FastEthernet0/0
On r2:
!
router ospf 1
router-id 192.168.123.2
log-adjacency-changes
network 23.0.0.2 0.0.0.0 area 0
network 192.168.123.2 0.0.0.0 area 0
neighbor 192.168.123.3 cost 10
neighbor 192.168.123.1 cost 10
!
interface Ethernet1/0
ip address 192.168.123.2 255.255.255.0
ip ospf network point-to-multipoint non-broadcast
half-duplex
!
r2#show ip route ospf
192.168.123.0/24 is variably subnetted, 3 subnets, 2 masks
O 192.168.123.3/32 [110/1] via 23.0.0.3, 00:01:05, FastEthernet0/0
O 192.168.123.1/32 [110/2] via 23.0.0.3, 00:00:49, FastEthernet0/0
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/3] via 23.0.0.3, 00:00:49, FastEthernet0/0
On r3:
!
router ospf 1
router-id 192.168.123.3
log-adjacency-changes
network 23.0.0.3 0.0.0.0 area 0
network 192.168.123.3 0.0.0.0 area 0
neighbor 192.168.123.2 cost 10
neighbor 192.168.123.1 cost 1
!
interface FastEthernet0/0
ip address 192.168.123.3 255.255.255.0
ip ospf network point-to-multipoint non-broadcast
!
