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DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
Field Description
Link State Age The time is seconds since the link state advertisement was
originated.
Options The optional capabilities supported by the described portion of
the routing domain.
Link State Type The type of the link state advertisement. Each link state type
has a separate advertisement format. The link state type are as
follows:
Type Description
1 Router Links
2 Network Links
3 Summary Link (IP Network)
4 Summary Link (ASBR)
5 AS External Link
Link State ID This field identifies the portion of the internet environment that
is being described by the advertisement. The contents of this
field depend on the advertisement’s Link State Type.
Advertising Router The Router ID of the router that originated the Link State
Advertisement. For example, in network links advertisements
this field is set to the Router ID of the network’s Designated
Router.
Link State Sequence
Number
Detects old or duplicate link state advertisements. Successive
instances of a link state advertisement are given successive Link
State Sequence numbers.
Link State Checksum The Fletcher checksum of the complete contents of the link
state advertisement, including the link state advertisement
header except for the Link State Age field.
Length The length in bytes of the link state advertisement. This
includes the 20-byte link state advertisement header.
Table 5-16. Link-State Advertisement Header
Router Links Advertisements
Router links advertisements are type 1 link state advertisements. Each router in an area originates a
routers links advertisement. The advertisement describes the state and cost of the router’s links to the
area. All of the router’s links to the area must be described in a single router links advertisement.
The format of the Router Links Advertisement is shown below:
80