3Com 4007, Руководство по внедрению, Страница: 479 / 684

Link State Databases 479
Each external link state advertisement includes this information:
■
LSID (Link State ID) — An IP network address:
■
For Type 3 summary link advertisements , this is the IP network
number.
■
For Type 4 summary link advertisements , this is the ASBR’s
router ID.
■
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 — The IP address mask for the advertised destination.
■
Fwd address (Forwarding Address) — If the AS boundary router is
advertising a destination that can be more optimally reached by a
different router on the same LAN, then the advertising boundary
router specifies that router’s address in the forwarding address field.
Otherwise, it leaves the field as 0.
■
Metric — The cost to reach the advertised destination.
■
Type — Possible values:
■
Type 1 — Normal link state metric.
■
Type 2 — The metric is larger than any local link state path. See
the discussion of Type 1 and Type 2 external metrics earlier in this
section.
■
Route Tag (External)
— Not used by OSPF. These 32-bits may be
used to communicate other information between boundary routers.
Important
Considerations
When you view the link state database, consider the following:
■
An asterisk (*) after the router ID in a display indicates that the LSA
originated locally.
■
All routers within an area must maintain identical link state databases.
■
Use the contents of the link state database for network configuration
and troubleshooting purposes.