User manual

xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
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Link-State Advertisement Header
Link-State Age
Options Link-State Type
Link-State ID
Advertising Router
Link-State Sequence Number
Link-State Checksum
Length
Figure 8- 22. Link State Advertisement Header
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: Router Links, Network Links,
Summary Link (IP Network), Summary Link (ASBR), 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 by accepting
the Link State Age field.
Length The length in bytes of the link state advertisement. This includes the 20-
byte 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: