Specifications

282 ExtremeWare XOS 11.0 Concepts Guide
Interior Gateway Protocols
Virtual links are also used to repair a discontiguous backbone area. For example, in Figure 49, if the
connection between ABR1 and the backbone fails, the connection using ABR2 provides redundancy so
that the discontiguous area can continue to communicate with the backbone using the virtual link.
Figure 49: Virtual link providing redundancy
Point-to-Point Support
You can manually configure the OSPF link type for a VLAN. Table 48 describes the link types.
NOTE
The number of routers in an OSPF point-to-point link is determined per VLAN, not per link.
Table 48: OSPF link types
Link Type Number of Routers Description
Auto Varies ExtremeWare XOS 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 This type synchronizes faster than a broadcast link because routers do
not elect a DR or BDR. It does not operate with more than two routers
on the same VLAN. The Point-to-Point Protocol (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 designated router (DR) or
backup designated router (BDR). If you have three or more routers on
the VLAN, OSPF fails to synchronize if the neighbor is not configured.
Passive A passive link does not send or receive OSPF packets.
ABR 1 ABR 2
EX_045
Area 2
Area 0
Area 1 Area 3
Virtual link