D-Link DES-3326S - Manual (Page 163)

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
Switch Management and Operating Concepts 163
Figure 5-31. Summary Link Advertisement
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.
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.
Otherwise, routes for the other TOS values are also described.
If a cost for a certain TOS is not included, its cost defaults to
that specified for TOS 0.
Field Description
Network Mask For Type 3 link state
advertisements, this
indicates the destination
network’s IP address
mask. For example,
when advertising the
location of a class A
network the value
0xff000000
TOS The Type of Service that
the following cost is
relevant to.
Metric The cost of this route.
Expressed in the same
units as the interface
costs in the router links