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476 C
HAPTER
19: O
PEN
S
HORTEST
P
ATH
F
IRST
(OSPF) R
OUTING
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Link ID — Identifies the object to which this router link connects for
each Link Type. Possible values:
■
If Link Type is PTP , then this is the neighboring router’s router ID.
■
If Link Type is Transit
, then this is the address of the designated
router.
■
If Link Type is Stub , then this is the IP network or subnetwork
number.
■
If Link Type is Virtual Link , then this is the neighboring router’s
router ID.
■
Link Data — Provides additional link information. Possible values:
■
If Link Type is PTP , then this is the MIB II index value for an
unnumbered point-to-point interface.
■
If Link Type is Transit , then this is the IP address of the advertising
router’s interface.
■
If Link Type is Stub , then this is the network’s IP address mask.
■
If Link Type is Virtual Link , then this is the IP address mask of the
neighboring router.
■
Metric — Cost of using this outbound router link. With the exception
of stub networks, this value must be other than 0.
Network Link State
Advertisements
The designated router for each area originates a network link state
advertisement for each transit network — a network that has more than
one attached router. This advertisement describes all routers that are
attached to the network, including the designated router itself. Each
network link state advertisement (LSA) includes this information:
■
LSID (Link State ID) — The ID of the router that generated the LSA.
■
Router ID — ID of the router that originated the LSA .
■
LS Seq (Link State Sequence) — The sequence number of the
advertisement. Used to detect old or duplicate link state
advertisements.
■
LS age — The time, in seconds, since the LSA was generated.
■
Network Mask — IP address mask for the network.
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Attached Routers — List of routers that are fully adjacent to the
designated router (DR). The ID of the DR is also listed here.