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DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
network’s IP address mask. For other link types the Link Data specifies the router’s associated IP
interface address.
Field Description
Type A quick classification of the router link. One of the following:
Type Description
1 Point-to-point connection to another router.
2 Connection to a transit network.
3 Connection to a stub network.
4 Virtual link.
Link ID Identifies the object that this router link connects to. Value
depends on the link’s Type. When connecting to an object that
also originates a link state advertisement (i.e. another router or
a transit network) the Link ID is equal to the neighboring
advertisement’s Link State ID. This provides the key for
looking up an advertisement in the link state database.
Type Link ID
1 Neighboring router’s Router ID.
2 IP address of Designated Router.
3 IP network/subnet number.
4 Neighboring router’s Router ID
Link Data Contents again depend on the link’s Type field. For connections
to stub networks, it specifies the network’s IP address mask.
For unnumbered point-to-point connection, it specifies the
interface’s MIB-II ifIndex value. For other link types it specifies
the router’s associated IP interface address. This latter piece of
information is needed during the routing table build process,
when calculating the IP address of the next hop.
No. of TOS The number of different Type of Service (TOS) metrics given for
this link, not counting the required metric for TOS 0. If no
additional TOS metrics are given, this field should be set to 0.
TOS 0 Metric The cost of using this router link for TOS 0.
Table 5-18. Routers Links Advertisements − Continued
For each link, separate metrics may be specified for each Type of Service (TOS). The metric for TOS 0
must always be included, and was discussed above. Metrics for non-zero TOS are described below. Note
that the cost for non-zero TOS values that are not specified defaults to the TOS 0 cost. Metrics must be
listed in order of increasing TOS encoding. For example, the metric for TOS 16 must always follow the
metric for TOS 8 when both are specified.
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