Extreme Networks ExtremeWare 7.2e, Installation And User Manual

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Overview of OSPF
ExtremeWare 7.2e Installation and User Guide 239
Figure 47: Virtual link providing redundancy
Point-to-Point Support
You can manually configure the OSPF link type for a VLAN. Table 42 describes the link types.
NOTE
The number of routers in an OSPF point-to-point link is determined per-VLAN, not per-link.
NOTE
All routers in the VLAN must have the same OSPF link type. If there is a mismatch, OSPF attempts to
operate, but may not be reliable.
Table 42: OSPF Link Types
Link Type Number of Routers Description
Auto Varies ExtremeWare automatically determines the OSPF link type based on
the interface type. This is the default setting.
Broadcast Any Routers must elect a designated router (DR) and a backup designated
router (BDR) during synchronization. Ethernet is an example of a
broadcast link.
Point-to-point Up to 2 Synchronizes faster than a broadcast link because routers do not elect
a DR or BDR. Does not operate with more than two routers on the
same VLAN. PPP is an example of a point-to-point link. An OSPF
point-to-point link supports only zero to two OSPF routers and does not
elect a DR or BDR. If you have three or more routers on the VLAN,
OSPF will fail to synchronize if the neighbor is not configured.
Passive A passive link does not send or receive OSPF packets.
ABR 1 ABR 2
EW_017
Area 2
Area 1 Area 0 Area 3
Virtual link