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124 Cards in this Set
- Front
- Back
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What does it mean to be a link-state protocol?
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We could think of a link as being an interface on the router. The state of the link is a description of that interface and of its relationship to its neighboring routers. A description of the interface would include, for example, the IP address of the interface, the mask, the type of network it is connected to, the routers connected to that network and so on. The collection of all these link-states would form a link-state database.
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Common characteristics of OSPF. hint subnet mask in update, summarization characteristics (2), how to calculate best path
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VLSM support, no autosummarization, topology summariztion, uses SPF algorithm based on dijstrka's algorithm
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What is the IP port number and multicast address?
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IP protocol 89 and 224.0.0.5 (allSPFrouters) and 224.0.0.6 (allDRrouters)
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What are the 5 packet types? Are LSAs a Packet type?
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Hello, DBD, LSUpdate, LSAck, LSRequest. NO LSA are contained in LSU and summarized in DBD.
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Configure Basic OSPF. How can interface be added to OSPF?
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router ospf 1 network area router-id Interface can be added with network statement or network commmand under routing process.
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How is router id determined? Does it need to be valid?
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Router id is essential to building the graph. If not manually configured with router-id under process then it is highest IP address if loopback and then highest interface address. It must be unique in the domain.
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What are the interface states for the interface state machine? How is interface state derived?
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Down, PtP, PtM, Loopback, and Waiting which leads to DR, BDR, or DRother. State is derived by network type or encapsulation.
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When building an OSPF neighbor what purpose does hello serve? Hello timers and Dead Time?
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Hello detects neighbors, checks for compatibility, and determines liveliness. 10/40 (broadcast and PtP) or 40/120 non-broadcast (like EIGRP is higher) and PtM
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What are the possible neighbor states for OSPF?
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Down, Attempt, Init, 2-Way, Exstart, Exchange, Loading, Full.
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Describe Down and Attempt
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Down - statically configured neighbor but no hello receivedAttempt - only seen on nonbroadcast or PtM. If nothing is heard before dead interval neighbor is moved to down and contact rate reduced.
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Describe Init and 2Way
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Init is when I have seen neighbors hello but they don't report be in the Active Neighbor list. Which means they haven't seen my hellos.2Way occurs when both neighbors have seen each others hellos and are being reported in each other's active neighbor list. In 2way it is described as having formed a neighbor. An adjacent neighbor is when it is full.
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What components must be equal to become an 2WAY neighbor?
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Common subnet, same OSPF area, same hello and dead timer, Authentication, Stub Flags, MTU (will hurt exstart state), and other optional capabilities like NSF and opqaue LSA
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Describe Exstart and Exchange.
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Exstart is when the election occurs for who will be master and slave during database exchange. The first empty DBD with MS (Master), I (Initial), and M (more) bit are all set to 1 sent by both devices with SEQ x. The device with highest RID address will become master. The slave with reply with MS and I bit cleared with SEQ x to ack. Now exhange can start The master will send next packet with MS and M bit to 1 and SEQ x plus 1. The slave will piggyback DBD in the ACK with SEQ x +1 and M bit to 1 if there is more data to send. If the master finishes sending data first it must continue sending empty DBD so slave can piggyback of the connection.
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Describe Loading and Full
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While the DBD are being exchanged each router is building a LSRequest List for LSA it needs. It will know it needs it if the LSA is not in database or if LSA has higher maxage or higher sequence number. LSRequest is sent and LSU are reply. LSAck sent in reponse to LSU. Each of the LSA that is sent by each router will be added to their retransmission list on the interface.It is full when Request list is empty.
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Describe purpose of DR/BDR. What about LSA?
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DR and BDR are an optimization on multiaccess segments for routers when building the topology map. Instead of each saying they have ptp to each router on segment they basically suggest that they have ptp to the psueonode - the DR. In the router LSA this is describes link as transit with a DR address and my local address. This address is the type 2 LSA which describes all of the routers on the segment.
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Describe DR/BDR election process?
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When broadcast or non-broadcast interfaces come up they enter into Waiting period based on dead time (40 or 120). During the state routers are trading hello packets with empty DR/BDR and entering 2way if possible. Once wait time is over the routers goes into election. The election is local based on the information contained in the hello packets. Highest IP ospf priority and then highest RID.
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Since DR/BDR election is local what happens if a router enters election before other routers?
What happens with LSA Type 2 if there are no other routers on the segment? |
The wait time could end sooner. If a router sees with a DR/BDR listed it will begin election locally as well. Should come to same answer.
Router doesn't generate type 2 LSA and just includes the network as STUB |
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Is role preemptive? What if DR fails and DROTHER has better priority than BDR? What if router sees another device claiming a different DR?
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Role is not preemptive.
If DR fails and a DROTHER has a better priority it will not assume the role as DR. The BDR will become DR and a new election for DR will occur. There are corner cases where device was not able to hear hello with DR/BDR announcement so it claims something different and then election must occur. But it is not possible to lower priority and force election. |
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How to configure router to not be apart of election? What topologies is this important?
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Int g0/0
ip ospf priority 0 Hub and Spoke. |
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3.6.d [i] Point-to-point, multipoint, broadcast, non-broadcast
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3.6.d [i] Point-to-point, multipoint, broadcast, non-broadcast
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What are the OSPF network types? Which network types are not a default option?
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Broadcast, NonBroadcast, PtP, PtM and PtM nonbroadcast, loopback (valid for only loopback and not configurable)PtM and PtM nonbroadcast (this is not a default option),
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If you don't config network type how is it derived? What the purpose of network type?
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Interface encapsulation determines network type. Network type determines hello and dead timers, how many neighbors are supported, unicast or multicast support, DR/BDR, and next-hop address.
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What network types use multicast addressing? What use unicast addressing?
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mcast-Broadcast, ptp, and ptmucast - nonbroadcast and ptm nonbroadcast
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What network types use 10/40 hello/hold?What network types use 30/120 hello/hold?
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10/40-Broadcastand, ptp30/120-nonbroadcast, ptm, and ptm nonbroadcast
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What network types use DR/BDR?
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broadcast and nonbroadcast
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What network types set next-hop to advertising router?What network types set next-hop router on other end of link?
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Advertising Router - Broadcast and Nonbroadcast; link advertised as prefixOther End - PtP, PtM, PtMNB; link advertised as number of host entries
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Which interfaces are always advertised /32?
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ptm and loopback. If loopback is changed to ptp it advertise the actual subnet mask.
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What are the link types and how are they derived? What purpose?
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Stub, Transit, Virtual, PtP. It's first derived from presence of neighbor. If there is neighbor then can either be transit, virtual, or ptp. Used to build OSPF topology.
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If no neighbor detected what is the link type?
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Stub
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If neighbor is detected what is the link type on ptp, ptm, and ptmnb network type? broadcast? nonbroadcast? Virtual Link? Loopback?
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(1) ptp(2) transit(3) transit(4) Virtual(5) stub
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3.6.d [iii] Internal router, ABR, ASBR
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3.6.d [iii] Internal router, ABR, ASBR
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Describe an OSPF area. SPF and LSDB?
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Area is a collection of routers. LSDB per area and SPF is run inside of the area.
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What is purpose of area 0?
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Responsible for summarizing information between areas.
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What causes limitations to size of area?
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It is not the SPF that cause CPU problems but rather flooding and maintaining LSDB. Router capabilitiles limit size of OSPF area.
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What is an internal router, backbone router, area border router, ASBR?
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Internal router is a router inside a nonbackbone area. Backbone router is a router with an area 0 interface. Area Border Router has a non-backbone interface and an area 0 interface. An ASBR connects OSPF to another routing system. ASBR cannot be in a stub area.
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3.6.a Packet Types
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3.6.a Packet Types
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What are the LSA Types for OSPFv2?
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Type 1 Router LSA, Type 2 Network LSA, Type 3 Summary LSA, Type 4 ASBR LSA, Type 5 External LSA, Type 7 NSSA External, Type 9-11 area opaque LSA
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What is purpose of type 1 LSA? What kinds of routes are these? How are ptp links displayed? How are ptm links displayed?
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Type 1 router LSA is the router id and it has the links and their states (link type, network, cost). Routers use this LSA within an area. These are considered internal (O) routes.ptp have two data structures in LSA have a stub link to represent the network and a ptp which show local router and remote router.ptm have multiple data structures in LSA have a stub link of /32 for my interface and a ptp for each router I'm connected to.
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What is purpose of type 2 LSA? What kind of routes are these?
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Inside of type 1 you can have a transit link type which identifies the DR. The type 2 LSA identifies the attached routers and the network masks. These are considered internal (O) routes.
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What is purpose of type 3 LSA? What kind of routes are these?
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Type 3 LSA summarize information between areas. Stub networks will be turned into type 3 LSAs and advertised by ABR. The ABR will take the cost from itself and advertise that into the area. So other internal routers believe this is a network connected to the ABR. That is why the information is considered summarized. Changes in topology don't require a full SPF run and this is considered distance vector so loop avoidance is different. These are (OIA) routes or OSPF interarea routes.
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What is purpose of type 4/5 LSA? What kind of routes are these? Why a type 4/5 combo and not just type 5 with ABR changing advertising router?
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Type 4 describe the ASBR and set the ARB as the advertising router. The 5 LSA is the external prefix being routed and the advertising router is the ASBR. Not changing it supports understanding the originating router.
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What is an E1 vs E2? What is forward metric? What is default for redistribution?
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E1 is an external route type metric which suggests to calculate cost from redistribution and internal network (metric to ABR and ABR to ASBR) to get to destination.E2 suggests only consider the redistributed cost. However routers still use a foward metric when there are two ABRs advertising the same route. E2 is default with metric of 20.Foward address of all 0.0.0.0 says use the advertising router.
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What is purpose of type 7 LSA? What kind of routes are these?
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Type 7 is for NSSA. The forward address is the ASBR. You need this when you want to redistribute type 7 LSA into the area.
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Why is there distance vector behavior in OSPF?
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When ABR summarizes the information the routers don't see everything. It becomes a route by rumor from ABRs. So to prevent loops routers do not accept type 3s from a nonbackbone area. That way it is not looping routes. I will not accept from nonbackbone area if I am full on OSPF area 0.
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3.6.d [ii] LSA types, area type: backbone, normal, transit, stub, NSSA, totally stub
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3.6.d [ii] LSA types, area type: backbone, normal, transit, stub, NSSA, totally stub
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What's purpose of ospf stub configuration?
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Stub configuration limits the the type of LSA that go into an area. Type 4/5 are summarized into a type 3 default and type 1,2,3 can go into area. Stub config must be on all routers.router ospf 1 area 1 stub
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What's purpose of ospf totally stub area configuration?
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Stub configuration limits the the type of LSA that go into an area. Type 3,4/5 are summarized into a type 3 default and type 1,2,3 can go into area. Stub config must be on all routers but ABR must be configured with no-summary keywordrouter ospf 1 area 1 stub no-summary
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What's purpose of ospf NSSA stub area configuration? Does it advertise a default route instead? If so what type of LSA is the default?
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This configure blocks 4/5 but allows type 7s in area for external redistribution point on ASBR in NSSA.router ospf 1 area 1 nssaIt does not advertise a default because the ASBR could be. It can be done on any internal or ABR. ABR is unconditional and internal is conditional. As an LSA type 7.router ospf 1 area 1 nssa default-information-originate
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What's purpose of ospf NSSA totally stub area configuration? Does it advertise a default route instead? If so what type of LSA?
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This configure blocks 3, 4/5 but allows type 7s in area for external redistribution point on ASBR in NSSA. Yes and will only be done on ABR as type 3.router ospf 1area 1 nssa no-summary
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If there are multiple ABRs in an area there is a type 7 to 5 translation election. Why? How is election done? Drawbacks? Is there are type 4 LSA?
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Because of the forward address. Both routers would be advertising the same information essentially. Any router getting the type 5 would need to find a way to the forwarding address. That decision would be based on an OIA to the ASBR. Both routers will be sending an OIA to the ASBR. Highest RID wins election. However this could lead to control plane and data plane have different paths. There is no type 4 because of the forwarding address.
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If you have seperate paths with control plane and data plane because of 7 to 5 election how can this be fixed?
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Suppress the forwarding address so all that is left is the advertising router of the type 5 LSA. area 1 nssa no-summary translate type7 suppress-fa
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What's the purpose of this command? area 51 nssa no-redistribution no-summary
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This will cause a totally NSSA ASBR that is also the ABR to not send type 7s in the nonbackbone area but only the type 3 summary default. It will also not send type 3,4,5s.
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How to generate default cost for default route generated by stub command?
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area 1 default-cost xxxx
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3.6.e Implement and troubleshoot path preference
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3.6.e Implement and troubleshoot path preference
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OSPF Area Path Selection. What is the order?
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O, OIA, Type 1, and Type 2
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3.6.g [i] Metrics
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3.6.g [i] Metrics
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OSPF Metrics is derived from what? Formula?
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Cost = Ref_BW/Interface BW
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What are ways to change the cost?
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Interface bandwidth, interface cost command ip ospf cost x, auto-cost reference-bandwidth, neighbor xxx [cost]. The neighbor cost command only applies to PTM and doesn't make it unicast.
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When does OSPF add cost?
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Each router builds a map and so it does it on the outgoing.
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3.6.d [iv] Virtual link
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3.6.d [iv] Virtual link
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What is the purpose of a virtual link? Any restrictions?
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Virtual Links connect nonbackbone areas back to area 0. And they connect partitioned areas. Every nonbackbone area must be connected to area 0. This is how there routes are shared with the rest of the network and how they get summary routes. A virtual link is a control plane link only which is a unicast connection between the internal router and the ABR for them so share LSA. Cannot be in a stub area. Router ospf 1 area virtual-link
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What if virtual link is not an option?
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GRE tunnel.
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3.6.f [ii] Graceful shutdown
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3.6.f [ii] Graceful shutdown
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How to shutdown OSPF process? What happens?
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under routing process issue the shutdown command or on the interface enter ip ospf shutdown. 1. Drop all OSPF neighbors, flush with 3600 maxage, send hello 0.0.0.0 for DR/BDR (causes new election), stop tx/rx OSPF hellos2. Drop all neighbors on interface, send update LSA without that interface, send hello 0.0.0.0 DR/BDR, stop tx/rx OSPF hellos on interface.
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3.6.f [iii] GTSM [Generic TTL Security Mechanism]
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3.6.f [iii] GTSM [Generic TTL Security Mechanism]
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What tool will control what TTL ospf will accept? How does it work? How is it configured?
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OSPF TTL Security Checks. When configured it changes the TTL to 255. The remote router will only accept TTL so many hops away. A TTL security hops of 2 says 255-2 or 253. The TTL must be 253 or greater for router to accept OSPF packet.Enable for all interfacesRouter ospf 100 tll-security all-interfaces hops Int f0/0 ip ospf ttl-security disableper interfaceint f0/0 ip ospf ttl-security hops
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3.6.g [iv] IP FRR/fast reroute [single hop]
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3.6.g [iv] IP FRR/fast reroute [single hop]
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What tool allows for redundant loop free paths to be installed in the routing table? Configure
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IP Fast Reroute (FRR) aka Loop Free Alternative (LFA). Install a loop free alternative path into the RIB. So if primary falls a backup comes in. Router ospf 1 fast-reroute per-prefix enable [area x] prefix-priority (priority-level) fast-reroute per-prefix tie-break (attribute) [required] index (index-level)
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If FRR is enable for an area what happens to exeternal routes?
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They are do not get a repair path. Must not include area to have router consider external routes.
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What is the prefix priority?
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Prefix priority low says create repair for all routes. High says create repair for those configured with high priority. Requires route-map.
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What does this command do? What are the attributes? fast-reroute per-prefix tie-break (attribute) [required] index (index-level)
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10 - Shared Risk Link Group (SRLG)-disjoint--Eliminates LFAs that belong to any of the protected path SRLGs. This is a manually configured value on the interface (srlg gid x)20 - Primary Path - eliminates LFA that a path that's part of the ECMP.30 - Interface-disjoint--Eliminates LFAs that share the outgoing interface with the protected path.40 - Lowest Metric --Prefer path with lowest metric 50 - Linecard-disjoint--Eliminates LFAs that share the line card with the protected path.60 - Node protecting - prefer path that doesn't go through same next-hop as primary70 - Broadcast-interface-disjoint--Eliminates LFAs that traverse the same broadcast domain as primary.256 - Load Sharing - Load share if still more than one remaining
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If you add required keyword to attribute what does that mean?
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It means the path must meet the parameters of attribute to be considered.
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3.6.g [v] LFA/loop-free alternative [multi hop]
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3.6.g [v] LFA/loop-free alternative [multi hop]
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What is remote LFA aka LFA multihop?
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It provides the ability to tunnel through problematic routers to establish a loop free path. The router is problematic because it is a neighbor but it would use me as it's path to the prefix. Let's say that neighbor had a neighbor that has another path. I could tunnel through that neighbor to build a backup path.
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What is required for Remote LFA to work?
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Basic MPLS with targeted LDP sessions.Router ospf 1 fast-reroute per-prefix remote-lfa [area area-id] tunnel mpls-ldpInterface x.x mpls ip mpls ldp discovery targeted-hello accept
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OSPFv3 prefix suppression
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OSPFv3 prefix suppression
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What tool allows OSPF to limit stub networks which are transitory in nature? How to configure
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Prefix suppression will remove the transit prefixs by suppressing the stub's for transit, ptp, and virtual. For the transit link the type LSA changes the mask to /32. For routers that don't support suppression this stub is ignored because it is not a valid mask.router ospf 1 prefix-suppressioninterface level interface f0/0 ip ospf prefix-suppresion
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3.6.g [ii] LSA throttling, SPF tuning, fast hello
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3.6.g [ii] LSA throttling, SPF tuning, fast hello
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What is flooding? Who can remove an LSA from the DB? Describe DB maintenance
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It is the process of sending LSU which contain LSA to neighbors. LSAck in response to the updates. The flood can be for one to many LSA. Only LSA can be removed by the advertising router with max-age. It must refresh the LSA every 30 minutes or half of LSA max age of 60 minutes. When the LSA is refreshed it gets a new sequence number.
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What do LSA sequence numbers range?
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0x80000001 - 0x7fffffff. What this actually is 0x80000001 - 0xffffffff then 0x00000001 to 0x80000000 at 0x8000000 the LSA is sent with max age and must be updated.
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How do LSA max-age increase?
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LSA max-age starts at 1 and counts up by 1 second. For each router it crosses it is also incremented by 1. The value can be changed with ip ospf transmit-delay
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OSPF hello timers..configure basic and subsecond.
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It is an interface configuration. The hello automatically updates the dead.ip ospf hello-intervalip ospf dead-intervalthe multiplier says how many hellos to send in a second.ip ospf dead-interval minimal hello-multiplier x
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Pacing Timerstimers pacing lsa-group 240timers pacing flood xxtimers pacing retransmission xx
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- Pacer timer thats tells router how long to wait when it needs to send an LSA because it has neared 30 minutes for refresh.- Configures space between LSU. Default is 33ms.- Configures space between LSU that must be retransmitted. Default is 66ms
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Throttle Timerstimers throttle spf 100 1000 10000 timers throttle lsa all 10 4000 6000
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- Throttles how frequently SPF can run.- Throttles how frequently LSAs can be generated.
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timers lsa arrival 2000ispf
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Mimumum interval between accepting same LSAispf enables SPF to run when changes only impact the tree
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Interface Timersinterface Serial0/1 ip ospf transmit-delay 2 ip ospf retransmit-interval 10
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- Adds two seconds to max age, default is 1- retransmission interval is how long to wait before resending LSA inside an LSU if no ack received.
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3.6.g [iii] LSA propagation control [area types, ISPF]
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3.6.g [iii] LSA propagation control [area types, ISPF]
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What does OSPF on demand circuit feature? Configure.
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Is suppresses hellos and LSA refresh by setting DNA so only application data will bring up underlying data link.int g0/0 ip ospf demand circuit
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int g0/0ip ospf flood-reduction
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Similar to demand circuit. This causes router to set DNA bit on all LSA and tells router to only update the LSAs when there is a change. This is configured per interface.
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router ospf 1 max-metric router-lsa
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This is the stub router feature and will cause router to increase metric to max on transit links. Causes router to not be transit router.
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router ospf 1 max-lsa xxx redistribute maximum-prefix xx
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- maximum number of lsa that can be made- max number of routes that can be redistributed.
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What are the available OSPF filtering techniques?
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Distribute List, Filter Lists, Area Range, summarization no advertise (area range and summary), database filter, administrative distance
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How can distribute lists be used? Is there are difference between in and out.
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Distribute List IN can be used to filter on routes from OSPF database to RIB. This is because the OSPF database must be the same within an area. Distribute list OUT can only be used on ASBR. Can work with ACL, Prefix-List, or Route-Map. router ospf 1 distribute-list route-map DENY_R3_LOOPBACK_FROM_R4 in
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How does a filter list work?
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OSPF filter list is used to filter on ABR between areas. IN means filter going into that area. Out means coming out of that area.Area filter-list prefix in | out
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How does the summary no advertise option work? area range no advertise?
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Summary no advertise is used on the ASBR and will suppress the subset along with summary.The area range no summary is used on the ABR and will suppress the subset along with summary.
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How does Database Filter work? When does interface command work? What about neighbor?
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Database filter can be applied per interface or per neighbor. This will stop OSPF LSA from flowing out that interface. To make sure the network is still intact engineer must make sure the LSA can flow another way. Interface command works on all network types. Neighbor command only works on ptmnb.
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Title OSPFv3 - 3.6.c [i] IPv4 address-family3.6.c [ii] IPv6 address-family 3.6.g [vi] OSPFv3 prefix suppression 3.6.a Describe packet types 3.6.a [i] LSA Types [1, 2, 3, 4, 5, 7, 9]
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Title OSPFv3 - 3.6.c [i] IPv4 address-family3.6.c [ii] IPv6 address-family 3.6.g [vi] OSPFv3 prefix suppression 3.6.a Describe packet types 3.6.a [i] LSA Types [1, 2, 3, 4, 5, 7, 9]
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What is OSPFv3?
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Routing Protocol for IPv6. I think it is better to think of it as a routing protocol with the ability to transport Ipv4 and IPv6 prefixes. There are also some improvements to the LSDB.
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What similar between OSPFv3 and OSPFv2?
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Same Packet Types, Same Network Types, Same Flooding, Same interface and Neighbor states
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Is the RID a IPv6 address?
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No, the RID is still a 32 bit value.
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Must the RID be different for the address families? Must the RID be different for VRFs?
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No, the RID can be the same for all the addresses families. No the RID doesn't need to be different for the VRFs.
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What addresses are used with OSPFv3 for sending OSPF packets? What about Virtual Link?
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Link Local and Global used for Virtual Link
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What's the LA bit have to do with virtual link?
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The virutal link can only be established between global addresses. When VL is created router will add a global address to Intra-Area Prefix type 9 LSA with LA bit (local address) capability set. Routers will use this to create VL. Loopback with default network types are automatically added with LA bit.
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With OSPF v3 what new feature must be the same to form an adjacency? Describe the feature.
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The interface instance must be the same. The instance numbers allows to create groups on a multicaccess segment for peering. int f0/0 ipv6 ospf 1 area 0 instance 33
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Can interfaces be added to OSPFv3 using network commands?
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No, only with interface command.
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Does OSPFv3 support authentication?
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No, authentication support. IPv6 has the authentication and encryption.
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What are the LSA types for OSPFv3?
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Type 1 - RouterType 2 - NetworkType 3 - Inter-Area Prefix SummaryType 4 - Inter-Area RouterType 5 - AS-ExternalType 8 - Link LocalType 9 - Intra-Area Prefix
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What are the function of router, link local, and intra-area prefix LSAs?
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The router LSA shows the neighboring router ID on ptp or transit. The router then locates the link local to determine next-hop. Then it can look at Intra-Area prefix to determine stubs.
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What has changed with the network LSA with OSPFv3?
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In the router LSA for transit lists the DR address. The LSA ID for network LSA is the DR. In the LSA it doesn't list stub anymore just the attached routers by router id.
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Each router must originate what LSA? What differs from OSPFv2?
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Type 1, 2, 8, and 9. OSPFv2 only required type 1 and 2.
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Why add the type 8 and 9 LSA to OSPFv3?
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I believe address change leads to full OSPF with OSPFv2. With v3 this doesn't happen.
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What are the two ways to configure OSPFv3?
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Classic Configuration and Address Family Mode
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What does classic configuration look like?
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Ipv6 unicast-routing!Ipv6 router ospf 1 Router-id 0.0.0.1 !Int s1/0 Ipv6 ospf 1 area 0
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What purpose of address family configuration? What does it look like?
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The purpose is to allow OSPFv3 to handle both IPv4 and IPv6 address family. interface Serial0/0/0 ipv6 address 2001:DB8:0:1::1/64 ip address 10.0.1.1 255.255.255.0 ospfv3 hello-interval 1 ! Applies both to IPv4 and IPv6 AF ospfv3 network point-to-point ! Applies both to IPv4 and IPv6 AF ospfv3 1 ipv6 area 0 ospfv3 1 ipv4 area 0 ! router ospfv3 1 address-family ipv4 area 1 range 10.1.0.0 255.255.0.0 ! address-family ipv6 area 1 range 2001:DB8:1::/48
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Does OSFPv3 have same adjacency for IPv6 and IPv4 address family?
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No, it is a separate adjacency family for each family. And separate database, hellos, etc. What is same is it is configured under one process and IPv6 address is used for both as transport where classic mode uses IPv4 as transport for OSPFv2 and IPv6 for transport of OSPFv3
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When OSPFv3 transports IPv4 does it tunnel IPv4?
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No you must have IPv4 configured from end to end. OSPFv3 really is just a configuration optimization. Allows you to configure v4 and v6 under one process.
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Describe the AF bit.
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When running OSPFv3 the AF bit is sent in the hellos for IPv4 AF. If the remote router supports IPv4 AF it will form an adjacency. It doesn't set the bit for IPv6. This enables backwords capability.
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How does prefix suppression work? How is it configured?
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Prefix removes the transit links leaving on the stubs. It suppresses the prefixes in the type 8 and type 9. With type 8 it removes the "stub" network leaving only the link local address and type 9 it removes the transit links because they aren't marked with the LA bit.Per interfaceInterface x/x ipv6 ospf prefix-suppression !per process Ipv6 router ospf 1 prefix-suppression
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How is shutdown different from OSPFv3 vs OSPFv2?
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-Shutdown command is much more gradual. Wait for all neighbor to die. Can be applied to interface, router ospfv3, or address family.
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AD, Summarization
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AD, Summarization |
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What about administrative distance?
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Admin Distance can be configured on neighbor. AD of 255 for neighbor along with route-map will not allow to enter routing table.
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2 ways to perform summarization?
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Summary address and Area range
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How to perform summarization on ABR?
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Area Range command. This command can only grab the type 1,2. It cannot be done on the ABR going into the area. Only when leaving the area.Router ospf 1 area range
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How to perform summarization on ASBR?
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Only applies to external routes on ASBR. The summary is not added locally like EIGRP.Router ospf 1 summary-address 112.12.128.0 255.255.252.0
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