D-Link DES-3326SRM Product Manual - Page 182
Network Links Advertisements
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D-Link DES-3326S Layer 3 Switch Network Links Advertisements Network links advertisements are Type 2 link state advertisements. A network links advertisement is originated for each transit network in the area. A transit network is a multi-access network that has more than one attached router. The network links advertisement is originated by the network's Designated router. The advertisement describes all routers attached to the network, including the Designated Router itself. The advertisement's Link State ID field lists the IP interface address of the Designated Router. 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: Network Link Advertisements Link-State Age Options 2 Link-State ID Advertising Router Link-State Sequence Number Link-State Checksum Length Network Mask Attached Router Table 11. Network Link Advertisement Field Network Mask Attached Router Description The IP address mask for the network. 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. 172