280
C
HAPTER
28: OSPF C
ONFIGURATION
OSPF has two types of route summarization:
1
ABR route summarization
To distribute routing information to other areas, an ABR generates Type-3 LSAs on
a per network segment basis for an attached non-backbone area. If contiguous
network segments are available in the area, you can summarize them with a single
network segment. The ABR in the area distributes only the summary LSA to reduce
the scale of LSDBs on routers in other areas.
2
ASBR route summarization
If summarization for redistributed routes is configured on an ASBR, it will
summarize redistributed Type-5 LSAs that fall into the specified address range. If in
an NSSA area, it also summarizes Type-7 LSAs that fall into the specified address
range.
If this feature is configured on an ABR, the ABR will summarize Type-5 LSAs
translated from Type-7 LSAs.
Route types
OSPF prioritize routes into four levels:
■
Intra-area route
■
Inter-area route
■
Type-1 external route
■
Type-2 external route
The intra-area and inter-area routes describe the network topology of the AS,
while external routes describe routes to destinations outside the AS.
OSPF classifies external routes into two types: Type-1 and Type-2. A Type-1
external route is an IGP route, such as a RIP or static route, which has high
credibility and whose cost is comparable with the cost of an OSPF internal route.
The cost from a router to the destination of the Type-1 external route= the cost
from the router to the corresponding ASBR+ the cost from the ASBR to the
destination of the external route.
A Type-2 external route is an EGP route, which has low credibility, so OSPF
considers the cost from the ASBR to the destination of the Type-2 external route is
much bigger than the cost from the ASBR to an OSPF internal router. Therefore,
the cost from the internal router to the destination of the Type-2 external route=
the cost from the ASBR to the destination of the Type-2 external route. If two
routes to the same destination have the same cost, then take the cost from the
router to the ASBR into consideration.
Classification of OSPF
Networks
OSPF network types
OSPF classifies networks into four types upon the link layer protocol:
■
Broadcast: When the link layer protocol is Ethernet or FDDI, OSPF considers the
network type broadcast by default. On Broadcast networks, packets are sent to
multicast addresses (such as 224.0.0.5 and 224.0.0.6).
Summary of Contents for 4800G Series
Page 26: ...26 CHAPTER NETWORKING APPLICATIONS ...
Page 30: ...30 CHAPTER 1 LOGGING IN TO AN ETHERNET SWITCH ...
Page 62: ...62 CHAPTER 3 LOGGING IN THROUGH TELNET ...
Page 70: ...70 CHAPTER 5 LOGGING IN THROUGH WEB BASED NETWORK MANAGEMENT SYSTEM ...
Page 72: ...72 CHAPTER 6 LOGGING IN THROUGH NMS ...
Page 82: ...82 CHAPTER 8 CONTROLLING LOGIN USERS ...
Page 98: ...98 CHAPTER 9 VLAN CONFIGURATION ...
Page 108: ...108 CHAPTER 10 VOICE VLAN CONFIGURATION ...
Page 119: ...GVRP Configuration Examples 119 DeviceB display vlan dynamic No dynamic vlans exist ...
Page 120: ...120 CHAPTER 11 GVRP CONFIGURATION ...
Page 160: ...160 CHAPTER 17 PORT ISOLATION CONFIGURATION ...
Page 172: ...172 CHAPTER 19 LINK AGGREGATION CONFIGURATION ...
Page 196: ...196 CHAPTER 22 DLDP CONFIGURATION ...
Page 240: ...240 CHAPTER 23 MSTP CONFIGURATION ...
Page 272: ...272 CHAPTER 27 RIP CONFIGURATION ...
Page 364: ...364 CHAPTER 29 IS IS CONFIGURATION ...
Page 426: ...426 CHAPTER 31 ROUTING POLICY CONFIGURATION ...
Page 442: ...442 CHAPTER 33 IPV6 RIPNG CONFIGURATION ...
Page 466: ...466 CHAPTER 35 IPV6 IS IS CONFIGURATION ...
Page 488: ...488 CHAPTER 36 IPV6 BGP CONFIGURATION ...
Page 498: ...498 CHAPTER 37 ROUTING POLICY CONFIGURATION ...
Page 540: ...540 CHAPTER 40 TUNNELING CONFIGURATION ...
Page 552: ...552 CHAPTER 41 MULTICAST OVERVIEW ...
Page 604: ...604 CHAPTER 43 MLD SNOOPING CONFIGURATION ...
Page 628: ...628 CHAPTER 46 IGMP CONFIGURATION ...
Page 700: ...700 CHAPTER 48 MSDP CONFIGURATION ...
Page 812: ...812 CHAPTER 57 DHCP SERVER CONFIGURATION ...
Page 822: ...822 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 834: ...834 CHAPTER 61 BOOTP CLIENT CONFIGURATION ...
Page 850: ...850 CHAPTER 63 IPV4 ACL CONFIGURATION ...
Page 856: ...856 CHAPTER 64 IPV6 ACL CONFIGURATION ...
Page 860: ...860 CHAPTER 65 QOS OVERVIEW ...
Page 868: ...868 CHAPTER 66 TRAFFIC CLASSIFICATION TP AND LR CONFIGURATION ...
Page 888: ...888 CHAPTER 69 PRIORITY MAPPING ...
Page 894: ...894 CHAPTER 71 TRAFFIC MIRRORING CONFIGURATION ...
Page 904: ...904 CHAPTER 72 PORT MIRRORING CONFIGURATION ...
Page 930: ...930 CHAPTER 74 UDP HELPER CONFIGURATION ...
Page 990: ...990 CHAPTER 79 FILE SYSTEM MANAGEMENT CONFIGURATION ...
Page 1000: ...1000 CHAPTER 80 FTP CONFIGURATION ...
Page 1020: ...1020 CHAPTER 82 INFORMATION CENTER CONFIGURATION ...
Page 1038: ...1038 CHAPTER 84 SYSTEM MAINTAINING AND DEBUGGING ...
Page 1046: ...1046 CHAPTER 85 DEVICE MANAGEMENT ...
Page 1129: ...SSH Client Configuration Examples 1129 SwitchB ...
Page 1130: ...1130 CHAPTER 88 SSH CONFIGURATION ...
Page 1160: ...1160 CHAPTER 90 RRPP CONFIGURATION ...
Page 1180: ...1180 CHAPTER 91 PORT SECURITY CONFIGURATION ...
Page 1192: ...1192 CHAPTER 92 LLDP CONFIGURATION ...
Page 1202: ...1202 CHAPTER 93 POE CONFIGURATION ...
Page 1218: ...1218 CHAPTER 96 HTTPS CONFIGURATION ...