D-Link xStack DXS-3350SR Installation & User Manual - page 165
DXS-3350SR Gigabit Layer 3 Switch
The distance form the network to all attached routers is zero, for all TOS. This is why the TOS and metric fields need not
be specified in the network links advertisement.
The format of the Network Links Advertisement is shown below:
Link-State Age
Options
Link-State ID
Advertising Router
Link-State Sequence Number
Link-State Checksum
Length
Network Link Advertisements
2
Network Mask
Attached Router
Field Description
Network Mask
The IP address mask for the network.
Attached Router
The Router Ids of each of the routers attached to the network. Only
those routers that are fully adjacent to the Designated Router (DR)
are listed. The DR includes itself in this list.
Summary Link Advertisements
Summary link advertisements are Type 3 and 4 link state advertisements. These advertisements are originated by Area
Border routers. A separate summary link advertisement is made for each destination known to the router that belongs to the
Autonomous System (AS), yet is outside the area.
Type 3 link state advertisements are used when the destination is an IP network. In this case the advertisement’s Link State
ID field is an IP network number. When the destination is an AS boundary router, a Type 4 advertisement is used, and the
Link State ID field is the AS boundary router’s OSPF Router ID. Other that the difference in the Link State ID field, the
format of Type 3 and 4 link state advertisements is identical.
Link-State Age
Options
Link-State ID
Advertising Router
Link-State Sequence Number
Link-State Checksum
Length
2
Network Mask
Summary Link Advertisements
TOS
Metric
For stub area, Type 3 summary link advertisements can also be used to describe a default route on a per-area basis. Default
summary routes are used in stub area instead of flooding a complete set of external routes. When describing a default
summary route, the advertisement’s Link State ID is always set to the Default Destination
− 0.0.0.0, and the Network Mask
is set to 0.0.0.0.
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Separate costs may be advertised for each IP Type of Service. Note that the cost for TOS 0 must be included, and is always
listed first. If the T-bit is reset in the advertisement’s Option field, only a route for TOS 0 is described by the advertisement.