Mar 26, 2020 · CCDA FAQ: OSPF, BGP, Route Manipulation, and IP Multicast Q1. True or false: A router needs to have all its interfaces in Area 0 to be considered an OSPF backbone router. Answer: False. A router with one or more interfaces in Area 0 is considered an OSPF backbone router. Q2. True or false: OSPF IS-IS […]
Hello packets are OSPF packet Type 1. These packets are multicast periodically to 224.0.0.5 multicast address on all interfaces (unicast on virtual-links) enabling dynamic discovery of neighbors and maintain neighbor relationships. On broadcast and NBMA networks, Hello packets are used to elect DR and BDR. OSPF (Open Shortest Path First) is an interior routing protocol used in larger networks. With OSPF, a router that sees a change to its routing table or that detects a change in the network immediately sends a multicast update to all other routers in the network. A multicast route to a destination is used by some multicast routing protocols to create the information that is used to forward multicast data from hosts on the destination network of the route (known as reverse path forwarding).Examples of multicast routing protocols include: Multicast Open Shortest Path First (MOSPF), Distance Vector –Type 6 (Multicast OSPF) - Spooky. See RFC1584. –Type 7 (NSSA AS External Link Advertisements) – Sent by ASBR’s that are part of an NSSA (see ‘Stub Area’). Stub Area – A stub area is an area that only requires one path, rather than an optimal path.
Dec 11, 2016 · So all OSPF routers use this multicast address for Hello while only DR/BDR use this multicast for Link State Update. And any OSPF router which receives this multicast packet will look in the OSPF header to determine whether it is a Hello or is a Link State Update and then processes the packet appropriately.
The OSPF multicast group is a link-local multicast that gets sent to every switch interface, even with IGMP snooping enabled on the switch. OSPF only uses multicast on broadcast networks, and it is necessary in order to use DR and BDR, which are only on broadcast networks. OSPF runs directly over the IP network layer using protocol number 89. Destination IP address is set to neighbor's IP address or to one of the OSPF multicast addresses AllSPFRouters (224.0.0.5) or AllDRRouters (224.0.0.6). Use of these addresses are described later in this article. Every OSPF packet begins with standard 24-byte header. The Multicast Open Shortest Path First (MOSPF) protocol is an extension to OSPF to support multicast routing. MOSPF allows routers to share information about group memberships. OSPF in broadcast and non-broadcast networks [ edit ] MOSPF (Multicast Open Shortest Path First) is an extension to the OSPF (Open Shortest Path First) protocol that facilitates interoperation between unicast and multicast routers. MOSPF is becoming popular for proprietary network multicasting and may eventually supersede RIP (Routing Information Protocol).
MOSPF (Multicast OSPF) PIM Dense Mode; PIM (Protocol Independent Multicast) is the most popular multicast routing protocol which we will discuss in other multicast lessons. RPF (Reverse Path Forwarding) Multicast routing is vulnerable to routing loops.
Oct 22, 2013 · OSPF- MTU and Multicast question Thanks Rolf, I already read that document but didn't get a clear idea---for example- two routers are connected to each other and if router-A creates a OSPF packet bigger than the link MTU size the IP layer should fragment the packet and send it to Router-B unless the GF bit is set.