Cisco OSPF
Open Shortest Path First kommunicerar med multicast som alltid har ttl satt till 1. OSPF använder IP protokoll #89. RFC 2328
Type: Link State
Algorithm: Dijkstra
AD: 110
Metric: Cost (Bandwidth)
Protocols: IP
Contents
Grannskap
Neighbors måste komma överens om:
- Subnät/Mask
- Area
- Timers
- Olika router-ID
- Flaggor: Stub, NSSA
- MTU
- Authentication type
- Kompatibla nätverkstyper, DR-election eller ej
Rekommendationer
- Set your maximum LSA settings to keep from killing weak boxes
- Baseline your network so you know how many LSAs normally float around
- Configure LSA warnings to alert of problems
- Crash each type of box on your network in a lab environment so you know what it will do under stress.
Konfiguration
router ospf [process-id]
router-id for this OSPF process (in IPv4 address format)
router-id [OSPF router-id] log-adjacency-changes
Uppdatera reference bandwidth till 100G
router ospf 1 auto-cost reference-bandwidth 100000 exit
Enable routing on an IP network
network [network-number] [wildcard-mask] area [area-id]
Slå på routing för alla nät och styr grannskap/uppdateringar med passive-interface
passive-interface default network 0.0.0.0 0.0.0.0 area 0 no passive-interface [interface]
Enable MD5 authentication in Area 0
area 0 authentication message-digest
Enable OSPF authentication on an interface
interface [interface] ip ospf message-digest-key 10 md5 [password] exit
Default route
default-information originate
DR/BDR election, multiaccess network
interface [interface] ip ospf priority [number] #default 1 exit
Summarization
ABR
router ospf 1 area 10 range 10.10.0.0 255.255.252.0 exit
ASBR
router ospf 1 summary-address 10.10.0.0 255.255.252.0 exit
Tuning protocol parameters
ip ospf hello-interval seconds ip ospf dead-interval seconds ip ospf retransmission-interval seconds ip ospf transmit-delay seconds
Stub
No LSA type 5
area 1 stub
Stub bit is sent in hello packets
Totally Stubby
No LSA type 3,4,5. Default route only.
ABR
area 1 stub no-summary
Others
area 1 stub
NSSA
LSA type 7
area 1 nssa
NSSA Totally Stubby
LSA type 7. No LSA type 3,4.
area 1 nssa no-summary
Virtual Link
Virtual link är rekommenderat som backup- eller temporär anslutning.
R1
router ospf 1 network 10.0.1.0 0.0.0.255 area 1 network 1.1.1.0 0.0.0.255 area 0 area 1 virtual-link 3.3.3.3 #Router-ID
R3
router ospf 1 network 10.0.1.0 0.0.0.255 area 1 network 10.0.2.0 0.0.0.255 area 2 network 3.3.3.0 0.0.0.255 area 2 area 1 virtual-link 1.1.1.1 #Router-ID
Show
show ip ospf virtual-links
Diverse
Loopback
ip ospf network point-to-point exit
MTU mismatch
ip ospf mtu-ignore
Troubleshoot
show ip ospf neighbor ping 224.0.0.5 show ip ospf interface brief show ip protocols show ip ospf events show ip ospf border-routers
Reset database and neighbors
clear ip ospf process
