3. Introduction to OSPF
OSPF l giao th畛c 動畛c s畛 d畛ng ph畛 bi畉n nh畉t. Vi畛c n畉m
動畛c n坦 l m畛t i畛u r畉t quan tr畛ng.
G坦i tin OSPF:
- Data Link Frame:
- IP Packet:
+ 畛a ch畛 g畛i: multicast (224.0.0.5 (s畛 d畛ng cho all router) /
224.0.0.6 (s畛 d畛ng cho DR/BDR)).
+ Protocol Field = 89
- OSPF Packet Header:
+ Type code: Ch畛 ra lo畉i g坦i tin (Hello, Database Desc, Link
state Request, Link state Upate, Stae Ack.)
+ Router ID & Area ID: Ph但n bi畛t gi畛a c叩c router v khu v畛c
s畛 d畛ng.
4. OSPF Packet Types
1. Hello: Ph叩t hi畛n v t叩i ph叩t hi畛n c叩c router hng x坦m, thi畉t
l畉p m畛i quan h畛 adjacency.
2. Database Description (DBD): 畛ng b畛 c董 s畛 d畛 li畛u gi畛a
c叩c router. Trong m畛t area, c叩c router ph畉i c坦 m畛t csdl
(topology) gi畛ng h畛t nhau.
3. Link-state Request (LSR): Y棚u c畉u v畛 m畛t v湛ng m畉ng.
4. Link-state Update (LSD): g畛i tr畉 v竪 c叩c th担ng tin cho
request ho畉c c畉p nh畉t s畛 thay 畛i trong v湛ng m畉ng.
5. Link-state Acknowledgement (LSAck): 畉m b畉o vi畛c truy畛n
tin tin c畉y.
5. Hello Packet
- G坦i tin hello 動畛c trao 畛i gi畛a 2 con neighbor v畛i nhau
tr動畛c khi thi畉t l畉p m畛i quan h畛 adjency.
C叩c tr動畛ng th担ng tin:
- Type:
- Router ID:
- Area ID:
- Network Mask: subnet mask c畛a interface g畛i i
- Hello Interval: 10s vs 30s
- Router Priority: L畛a ch畛n router DR hay BDR trong c叩c v湛ng
m畉ng Broadcast multiaccess.
- Router Dead Interval: = 4 l畉n hello interval (t動董ng t畛 holdtime
c畛a EIGRP).
- Designated Router (DR):
- Backup DR (BDR):
- List of neighbor(s):
6. Link-state Upade Packet
LSU chia thnh 10 lo畉i g坦i tin kh叩c nhau, ph畛 thu畛c vo c叩c
lo畉i router:
Type Description
1 Router LSAs
2 Network LSA: g畛i b畛i router DR, li畛t k棚 c叩c router ID
c畛a c叩c router trong v湛ng multiaccess.
3/4 Summary LSA: S畛 d畛ng 畛 c叩c router bi棚n, qu畉ng b叩
OSPF vo c叩c area kh叩c.
8. OSPF Configuration
R(config)#router ospf <proccess_ID>
process_ID k担 c畉n ph畉i gi畛ng nhau. (kh叩c vs EIGRP)
--> R(config-router)#network <network_address>
<wildcard_mask> area <area_number>
Trong gi叩o tr狸nh CCNA, ta s畛 d畛ng 董n v湛ng n棚n
<area_number> = 0.
Gi叩 tr畛 ny ph畉i chung nh畉t.
VD:
R(config)#router ospf 1
network 172.16.1.16 0.0.0.15 area 0
C嘆n m畛t vi c叩ch lm kh叩c:
- Th畛c hi畛n summary lu担n c叩c v湛ng m畉ng sau 坦 qu畉ng b叩.
- Ko quan t但m 畉n 畛a ch畛 c叩c interface:
c但u l畛nh: network 0.0.0.0 255.255.255.255 area 0.
9. C畉u h狸nh chu畉n
Khuy畉n c叩o s畛 d畛ng c叩ch sau 但y:
Ch畛 ra ch鱈nh x叩c 畛a ch畛 c畛a interface v wildcard mask =
0.0.0.0
--> Gi叩m s叩t 動畛c vi畛c ch畉y ospf tr棚n interface no.
Ex:
Router(config-router)#network 192.168.1.17 0.0.0.0 area 0
10. Router ID
S畛 d畛ng 畛nh danh cho c叩c router trong 1 area.
- 畛 畛nh danh router id cho m畛t router s畛 d畛ng ospf, ta c坦 th畛
d湛ng c但u l畛nh router-id v畛i vi畛c s畛 d畛ng 1 d畉i ip 畛 畛nh danh:
(config-router)#router-id 1.1.1.1 (example - n坦 ch畛 l 1 畛a ch畛).
- Trong tr動畛ng h畛p tr棚n router ko thi畉t l畉p router id, router s畉
l畛a ch畛n interface loopback c坦 畛a ch畛 ip cao nh畉t lm router id
(nh畛 l loopback nh辿 :D) --> khuy畉n ngh畛
- Trong tr動畛ng h董p ko s畛 d畛ng router id v loopback, n坦 s畉 l畉y
畛a ch畛 cao nh畉t c畛a interface m ang ho畉t 畛ng (active) lm
router id (i畛u ny c坦 ngh挑a l interface 坦 ko nh畉t thi畉t xi
OSPF).--> f動董ng f叩p ny k担 khuy畉n ngh畛, do c畛ng v畉t l箪 c坦 th畛
h畛ng.
11. Ki畛m tra Router ID
#show ip protocols
Details:
- Router ID 192.168.10.5
S畛 d畛ng Loopback lm ID: ch畛 c畉n t畉o ra loopback v g叩n 畛a
ch畛 IP cho n坦.
Ki畛m tra ho畉t 畛ng c畛a OSPF:
#show ip ospf neighbor
(Nh動 EIGRP)
Details:
Router ID Pri State Dead Time Address Interface
(neighbor) (local)
16. OSPF Network Type
- Point - to - Point
- Broadcast Multiaccess
- Nonbroadcast Multiaccess. VD: Frame Relay
- Point - to - Multipoint
- Virtual links.
17. Challenges in multiaccess Network
- Adjacency c坦 j kh叩c neighbors?
DR v BDR.
Trong v湛ng m畉ng multiaccess s畉 b畉u ch畛n ra m畛t router l DR,
m畛t router s畉 l BDR.
DR v BDR s畉 thi畉t l畉p adjacency v畛i t畉t c畉 router c嘆n l畉i.
Sending & Receiving LSA
18. DR/BDR Election
L畛a ch畛n DR/BDR nh動 th畉 no?
- DR 動畛c l畉y t畛 router c坦 Priority cao nh畉t, ti畉p theo l BDR
N畉u c湛ng priority? S畛 d畛ng Router ID.
Thay 畛i Priority
(config-if)#ip ospf priority {0 - 255}
Ch炭 箪:
- Qu叩 tr狸nh th畛c hi畛n l畛a ch畛n DR v BDR s畉 動畛c th畛c hi畛n
ngay khi router 畉u ti棚n ch畉y ospf.
- Khi DR c l畛a ch畛n, n坦 ti畉p t畛c lm cho 畉n khi x畉y ra:
+ DR fail.
+ OSPF ko c嘆n ch畉y tr棚n DR fail.
+ Interface ang k畉t n畛i vo v湛ng m畉ng multiaccess ko
ch畉y.
19. Force Election DR/BDR
T畉t h畉t interface i r畛i m畛 l畉i
shutdown
no shutdown
Ch畛n router c坦 priority cao nh畉t 畉u ti棚n.
20. Redistributing an OSPF Default route
t動董ng t畛 RIPv2:
(config-router)#default-information originate
Detail:
O*E2 (External Type 2).
Type 2: metric kh担ng thay 畛i.
Type 1: c畛ng th棚m cost c畛a 動畛ng link.
#6: 畛 畉m b畉o 2 con router l hng x坦m th狸 g坦i tin Hello 畛 2 con ph畉i c坦 nh畛ng tr動畛ng sau 但y l gi畛ng nhau: - Area ID; - Authentication type; - Network Mask: - Hello Interval ; - Router Dead Interval; - Router hi畛n t畉i f畉i th畉y m狸nh trong list of neighbor c畛a router hng x坦m. Ch炭 箪: Ch畛 c畉n sai kh叩c m畛t trong s畛 c叩c th担ng s畛 ny l ch畛u ch畉t!
#7: Trong OSPF, ta c坦 Area Backbone, c叩c area kh叩c s畉 k畉t n畛i v畛i area ny. Do 坦 t畛n t畉i kh叩c nhi畛u lo畉i router kh叩c nhau.
![Redistribution
Qu畉ng b叩 gi畛a c叩c giao th畛c 畛nh tuy畉n kh叩c nhau: RIPv2,
EIGRP, OSPF.
1. Qu畉ng b叩 EIGRP, OSPF vo RIP
router rip
redistribute eigrp 100 metric 1
redistribute ospf 1 metric 1
2. Qu畉ng b叩 RIP, OSPF --> EIGRP
router eigrp 100
redistribute ospf 1 metric 100000 100 255 1 1500
redistribute rip metric 100000 100 255 1 1500
3. Qu畉ng b叩 RIP, EIGRP --> OSPF
router ospf 1(m畉c 畛nh nh畉n vo l metric = 20)
redistribute rip [subnets] [metric-type 1] [metric 30]
redistribute eigrp 100 ....](https://image.slidesharecdn.com/12304329-120406210948-phpapp01/85/OSPF-25-320.jpg)