Qtech QSW-3900-48-SFP-DC [112/245] Protocols and standards

Qtech QSW-3900-48-SFP-DC [112/245] Protocols and standards
QTECH Software Configuration Manual
8-111
8.1.6.7 VPN
OSPF supports multi-instance, which can run on PEs in VPN networks.
In BGP MPLS VPN networks, multiple sites in the same VPN can use OSPF as the internal routing
protocol, but they are treated as different ASs. An OSPF route learned by a site will be forwarded to another site as an
external route, which leads to heavy OSPF routing traffic and management issues.
Configuring area IDs on PEs can differentiate VPNs. Sites in the same VPN are considered as directly
connected. PE routers then exchange OSPF routing information like on a dedicated line; thus network management
and OSPF operation efficiency are improved.
8.1.6.8 OSPF sham link
An OSPF sham link is a point-to-point link between two PE routers on the MPLS VPN backbone.
In general, BGP peers exchange routing information on the MPLS VPN backbone using the BGP extended
community attribute. OSPF running on a PE at the other end utilizes this information to originate a Type-3 summary
LSA as an inter-area route between the PE and CE.
If a router connects to a PE router in the same area and establishes an internal route (backdoor route) to a
destination, in this case, since an OSPF intra-area route has a higher priority than a backbone route, VPN traffic will
always travel on the backdoor route rather than the backbone route. To avoid this, an unnumbered sham link can be
configured between PE routers, connecting the router to another PE router via an intra-area route with a lower cost.
8.1.7 Protocols and Standards
· RFC 1765 : OSPF Database Overflow
· RFC 2328 : OSPF Version 2
· RFC 3101 : OSPF Not-So-Stubby Area (NSSA) Option
· RFC 3137 : OSPF Stub Router Advertisement
· RFC 3630 : Traffic Engineering Extensions to OSPF Version 2
8.2 OSPF Configuration list
OSPF Configuration list is as following :
Enable/disable OSPF
Configure router ID
Specify interface and area id
Configure area authentication type
Configure interface type
Configure interface cost
Configure priority when selecting DR
Configure Hello time interval
Configure interface invalid time of neighbour routers
Configure retransmission LSA time interval of neighbor router
Configure time needed when interface sending link state update packet
Configure packet authentication key
Configure STUB area of OSPF
Configure route convergence in OSPF
Configure OSPF virtual connection
Configure route introduced by OSPF other route protocol
Configure OSPF introduced default route
Configure external route parameter received by OSPF
OSPF monitor and maintain

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