routeprotocol

OSPFv3 packets use protocol 89, with communication using the routers link local interface address as the source. The destination address is either a unicast link local address or multicast link local address. ff02::05 OSPFv3 All Routers ff02::06 OSPFv3 Designated Routers Multicast addresses used in OSPFv3 communication Every router will use the multicast address FF02::5 to…

LS Type Name Description 0x2001 Router Describe the state and cost to reach a routers interface in an area 0x2002 Network A LSA that announces all of the routers attached to the link including itself 0x2003 Interarea Prefix Describes routes to IPv6 address prefixes that belong to other areas 0x2004 Interarea Router Announces the interface…

OSPFv3 protocols use the ID 89, with communication between different routers using the local interfaces IPv6 link local address. OSPFv3 link state advertisements are a little different from OSPFv2. For the Router link state advertisement, the network summary LSA is renamed the interarea prefix LSA. The ASBR summary link state advrtisement is renamed to interarea…

OSPFv3 is different from regular OSPF in an number of ways: Supports multiple address families: IPv4 is only supported in OSPFv2, OSPFv3 introduces support for IPv6 too! Additional LSA Types: For carrying IPv6 addresses. Removal of addressing semantics: Prefix information is no longer present in the OSPF packet headers. It is carried as a LSA…

Route filtering allows traffic flows to be manipulated at the area border router by filtering advertised routes to other routers. Filter by Summarisation The most simplistic method to filter a route for advertisement is to use the not-advertise option when configuring prefix summarisation. Using the not-advertise keyword prevents any type 3 LSAs being generated for…

Scalability of the routing protocol is an important factor for large networks such as service providers. By splitting up an OSPF network into multiple OSPF areas, it can reduce the size of the LSDB for that area. The number of routers and networks remain the same but Type 1 and Type 2 LSAs are exchanged…

If an OSPF topology is created, where traffic will need to cross a non-backbone area to reach a destination, it is known as a discontiguous network. The fix for a discontigious network is to ensure that Area 0 is contiguous. There are workarounds, such as GRE tunnels or a OSPF virtual link.

A Type 3 LSA represents an advertisement of a network from another area. Area Border Routers (ABRs) do not forward Type 1 or 2 LSAs between areas. If a ABR receives a Type 1 LSA from a area, it creates a Type 3 LSA referencing the network from the Type 1 LSA. The Type 2…

The Type 2 LSA represents a multi-access network segment (such as Ethernet) that utilises a DR/BDR. The DR always advertises the Type 2 LSA, which identifies all routers attached to the multi-access network segment. If a DR is not yet elected in the segment, there are no Type 2 LSAs in the LSDB. If a…

Every router in an OSPF network advertises a Type 1 LSA. The Type 1 LSA is a essential part within the link state database. An entry exists as a Type 1 LSA for every OSPF enabled link including its interface, and attached networks. Type 1 LSAs are not advertised outside of an area. The packet…