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

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 IP address format)

router-id [OSPF router-id] 
log-adjacency-changes

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-information originate

interface [interface]
ip ospf priority [number]
exit

ABR Summarization

router ospf 1
area 10 range 10.10.0.0 255.255.252.0
exit

ASBR Summarization

router ospf 1
summary-address 10.10.0.0 255.255.252.0
exit

Uppdatera reference bandwidth till 100G

router ospf 1
auto-cost reference-bandwidth 100000
exit

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