** introduction **
here i will cover one test env and configuration.
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** env description **
here i create area 1 , area 0 and area 2, in area2, esw5 has one default route and it will distribute to ospf area.
this case is verified with GNS3 with 1.4 version.
all the router has creeate one IP addr on loopback interface and will be the root id.
1) DR and BDR select
assume esw1 and esw2 startup with esw3 is still down
after esw1 startup, it will send one hello packet and then esw2 send hello packet. in the second hello packet, it will include the active neighbor. after both router is in two-way state, it start one timer to select the DR and BDR. during these time, it monitor the received hello packet, when it timerover, esw1 select esw2 as DR and it will fill it in the hello packet and send it.
and it will enter ex-start state. and two routers go full state.
then esw3 startup, it will send hello packet. it has the high root id
with the same priority, but esw1 has been DR, so esw3 is still DRother.
** Questions **
1) in Ethernet, hello packet is always sent with 224.0.0.5, is it correct ?
one strange thing is that i see hello is send to one specific IP.e.g. 2.2.2.2.
2) when update, DRother router send it to 224.0.0.6 and DR will send LSU with 224.0.0.5, all other router need ack it. does it ack to 224.0.0.6 or DR IP?
wireshark packets
** router info **
ESW1#show ip route ospf
10.0.0.0/24 is subnetted, 3 subnets
O IA 10.10.0.0 [110/2] via 10.10.1.3, 00:00:41, FastEthernet0/1
O IA 10.10.2.0 [110/3] via 10.10.1.3, 00:00:41, FastEthernet0/1
O*E2 0.0.0.0/0 [110/1] via 10.10.1.3, 00:00:41, FastEthernet0/1
ESW1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/BDR 00:00:34 10.10.1.2 FastEthernet0/1
3.3.3.3 1 FULL/DR 00:00:30 10.10.1.3 FastEthernet0/1
ESW1#show ip ospf database
OSPF Router with ID (1.1.1.1) (Process ID 1)
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 61 0x80000003 0x005B9F 1
2.2.2.2 2.2.2.2 61 0x80000003 0x001DD4 1
3.3.3.3 3.3.3.3 62 0x80000002 0x00E305 1
Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
10.10.1.3 3.3.3.3 62 0x80000001 0x0046B3
Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
10.10.0.0 3.3.3.3 102 0x80000001 0x003EDD
10.10.2.0 3.3.3.3 58 0x80000001 0x0032E6
Summary ASB Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
5.5.5.5 3.3.3.3 58 0x80000001 0x004ECB
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 5.5.5.5 107 0x80000001 0x00A4F9 1
** configuration **
interface Loopback0
ip address 1.1.1.1 255.255.255.255
interface FastEthernet0/1
no switchport
ip address 10.10.1.1 255.255.255.0
router ospf 1
router-id 1.1.1.1
log-adjacency-changes
network 10.10.1.0 0.0.0.255 area 1
interface Loopback0
ip address 2.2.2.2 255.255.255.255
interface FastEthernet0/2
no switchport
ip address 10.10.1.2 255.255.255.0
router ospf 1
router-id 2.2.2.2
log-adjacency-changes
network 10.10.1.0 0.0.0.255 area 1
interface Loopback0
ip address 3.3.3.3 255.255.255.255
!
interface FastEthernet0/3
no switchport
ip address 10.10.1.3 255.255.255.0
!
interface FastEthernet0/0
no switchport
ip address 10.10.0.3 255.255.255.0
!
router ospf 1
router-id 3.3.3.3
log-adjacency-changes
network 10.10.1.0 0.0.0.255 area 1
network 10.10.0.0 0.0.0.255 area 0
!
interface Loopback0
ip address 4.4.4.4 255.255.255.255
!
interface FastEthernet0/0
no switchport
ip address 10.10.0.4 255.255.255.0
!
interface FastEthernet0/1
no switchport
ip address 10.10.2.4 255.255.255.0
!
router ospf 1
router-id 4.4.4.4
log-adjacency-changes
network 10.10.0.0 0.0.0.255 area 0
network 10.10.2.0 0.0.0.255 area 2
!
interface Loopback0
ip address 5.5.5.5 255.255.255.255
!
!
interface FastEthernet0/1
no switchport
ip address 10.10.2.5 255.255.255.0
!
interface FastEthernet0/0
no switchport
ip address 10.10.3.5 255.255.255.0
!
ip route 0.0.0.0 0.0.0.0 10.10.3.1
!
router ospf 1
router-id 5.5.5.5
log-adjacency-changes
network 10.10.2.0 0.0.0.255 area 2
default-information originate always ---
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