Unicast Routing in IPv 6 Babu Ram Dawadi

Unicast Routing in IPv 6 Babu Ram Dawadi

Index a) What is a unicast routing protocol? b) Discuss about RIPng c) What are the Routing Table Entries of RIPng d) Explain RIPng Message Format e) What are different timers of RIPng f) What is OSPF? g) How do OSPF routers on the same link establish adjacencies? What does it mean to be adjacent? GWE. h) How do OSPF routers synchronize their Link State Databases? GWE. i) How to calculate the best route in OSPF? GWE. j) Learn how to see the above processes using ospfd, and ospf 6 d.

Unicast Routing Protocol l Unicast routing is a process that enable sender to send an unicast IP packets to the destination node. l 1 router or more intermediate routers may be used, depending to the destination of the node. (Figure 1) l Unicast routing protocol is a set of rules of forwarding unicast traffic from a source to a destination on an internetwork. The router is using only 1 port to forwards the received unicast packet Fig. 1. Unicast Routing

Unicast Routing Protocol l Unicast Routing Protocol consists of: – RIP (Routing Information Protocol) – OSPF ( – BGP l They each serve a different purpose. Routing Interior RIP Exterior OSPF Fig. 2. Types of Unicast Routing Protocol BGP

RIPng (RFC 2080) l Based on Distance Vector algorithm known as bellman ford algorithm l Router keeps the following entries in the routing table – IPv 6 Route • Address prefix and prefix length of the destination address – Next Hop Address • The IPv 6 Address (link-local) of the first router along the path – Next Hop Interface • The physical interface used to reach the next hop – Metric • Number indicating the total distance to the destination. RIPng advertizes directly connected routes with the configured outgoing metric of 1

RIPng routing table l Timer – Amount of time since the information about the route was last updated l Route change flag – Set to control triggered routing updates l Route Source – Entity to provide route information eg: Ripng, OSPF etc. .

RIPng Message Format l UDP based protocol using udp port number 521 IPv 6 UDP RIPng RTE 1 Header RTE 2 RTE 3 ……… RTEn 20 Bytes/RTE Command 1 B Version 1 B Unused 2 B 1: Request 2: Response l Command 1: ask system to send all or part of its routing table l Command 2: sends an update message containing all or parts of the senders routing table.

Routing Table Entry (RTE) l RIPng header is followed by one or more routing table entries (format of Routing table entry) 16 B 2 B …. Route Tag 1 B Prefix Length 1 B Metric(1 -16) IPv 6 Prefix

RTE. . l Route Tag – It may be used to carry additional information about a route learned from another routing protocol eg: BGP – The number of RTEs within single updates depends on the MTU of the medium between two neighboring routers – No of RTEs=[INT(MTU-IPv 6 Hdr len-UDP Hdr len -RIPng Hdr len) / RTE-Size] l Timers – RIPng uses different timers to control updates of the routing information – Update timer • By default, every 30 seconds, RIPng process wakesup on each interface to send an unsolicited routing response to the neighboring routers

Timer l Timeout Timer – Each time a route entry is updated and the timeout timer is reset to zero – If the route entry reaches 180 secs (default), without another update, it is considered to have expired, metric set to 16 and garbage collection process starts l Garbage collection timer (hold down timer) – Set to 120 secs (default) that have timeout or been received with a metric of 16 after expiration, the route entry finally be removed from the routing table.

OSPF l The difference between intra-domain and inter-domain (Fig. 2. ) – Routing within the same AS (Autonomous System) is referred to as intradomain. – Routing in the different AS (Autonomous System) is referred to as interdomain. l OSPF is an interior routing protocol – Intra-domain routing protocol a) Intra-domain b) Inter-domain Fig. 3. Interior Routing Protocol

OSPF Header IPv 6 Header NH: 89 40 Byte Version 1 B Packet Type 1 B Packet Length 2 B OSPF Header 16 Byte Router. ID 4 B Area. ID 4 B Checksum 2 B Instance ID 1 B Unused 1 B OSPF Message

OSPF Process l Link State routing – Each node within the autonomous system has the information about the entire topology. – Each node in the domain build up the routing table using Dijkstra’s algorithm. l Link State Database (LSDB) contains link state advertisement is send to every router in the same domain. – Each router will be updated with the latest copy of LSDB l Based on the LSDB, router creates a Shortest Path First (SPF) tree – Using Dijkstra’s a Algorithm l A routing table can be derived from the SPF tree which contains the best route to each router.

Types of OSPF Packets Type 1 Type 2 Database Description HELLO Router Link 0 x 2001 Network Link 0 x 2002 Type-7 -LSA 0 x 2007 Type 3 Link State Request Inter-Area-Prefix LSA 0 x 2003 Type 5 Type 4 Link State Update Inter-Area-Router LSA 0 x 2004 Link-LSA 0 x 0008 Fig. 4. Types of OSPF Packet Link State Acknowledgement AS-External-LSA 0 x 4005 Group. Membership-LSA 0 x 2006 Intra-Area-Prefix LSA 0 x 2003

How do OSPF routers on the same link establish adjacencies? What does it mean to be adjacent? GWE.

OSPF- Forming Adjacencies l OSPF routers on the same link establish adjacencies – Using Hello packet l An OSPF router need to go through 7 steps from no connection to full adjacency when it is first initialized. – – – – Down State Init State Two Way state Exstart Exchange State Loading State Full Adjacency

OSPF- Forming Adjacencies (cont) Down State No information has yet been exchanged. None Init State Routers send hello packets at regular intervals to establish relationships. Hello Packet (Type 1) Two-way State A router sees itself in a hello packet. Hello Packet (Type 1) Exstart Exchange State Loading State Full Routers negotiate master/slave relationship by comparing their router id using hello packets. Hello Packet (Type 1) Neighbors start communicating their link-state information with the others. Database Description (Type 2) The router has the initial information of each route, they may request for more complete information. Routers are fully adjacent. Link State Request Link State Update Link State Acknowledgement (Type 3, 4, 5) All (Type 1, 2, 3, 4, 5)

OSPF- Forming Adjacencies (cont) l Processing of Hello packet Fig. 5. Processing a Hello Packet (Reference: IPv 6 Essential Pg. 169)

OSPF- Forming Adjacencies (cont) The first OSPF neighbor is Down state. It means that no information (hellos) has been received from this neighbor. But it still can send Hello message to its neighbours Router 1 has seen the Router 2’s hello packet which had included its own Router ID within the received hello packet's neighbor field l Forming an adjacency – Phases – Packet type involved At this state, a router decides whether to become adjacent with this neighbor. The decision on adjacencies is always depend on the link media. (Types of network) Broadcast Multiple Access -DR and BDR are elected. Time Point to Point -No DR/BDR is needed or used because only 2 neighbour routers. Non-Broadcast Multiple Access -DR and BDR are elected Fig. 6. Forming an Adjacencies – Part I (Reference: IPv 6 Essential Pg. 170) Router 2 has received a hello packet from its neighbor, butreceived the Router 2 also has receiving router's was the Router 1’s hello. ID packet not included in the hello which had also included its packet own Router ID within the received hello packet's neighbor field . . . e e B nu i o t T n o C

OSPF- Forming Adjacencies (cont) l Types of Network: Broadcast Multiple Access Ethernet, Token Ring Point to Point Non Broadcast Multiple Access (NBMA) PPP, HDLC X. 25, Frame Relay Fig. 7. Types of Network

OSPF- Forming Adjacencies (cont) l When DR and BDR are elected, we can say that the adjacencies was established. l The DR and BDR are elected based on several criteria – – – DR – with highest router ID BDR – with second highest router ID Priority 0 will never be DR or BDR If priorities are same, the higher Router ID is elected. If DR fails, BDR becomes DR, and new BDR is elected. l After adjacent, the routers already created reliable channels to their neighbors. l These reliable channels is important for the routers to exchange Link State Database (LSDB) with the neighbors. .

How do OSPF routers synchronize their Link State Databases?

OSPF - Link State Databases The Router 1 is attempted to start the Exchange because “he” might thought that “he” has the highest Router ID After the election of Master and Routers enter Ex. Start Slave, the routers start Decide who is the Master and Slave. database descriptor exchange (DBD) packets. Router with the Highest ID will l When the routers have elected DR and BDR, the databases need to get synchronized – – – !But your DR/BDR become Master and only this router can increment the sequence number Each DBD packet has a It– might logic toelection conclude The Master/Slave is onsequence a per number basis which can be that-neighbor the DR/BDR with. Inthe incremented this state, the only by – Master/Slave election is irrelevant toand master actual exchangeexplicitly of highest. DR/BDR Router ID for will become election a network. by slave linkacknowledged state information ! But Router 2 will reply “No”. I will start the Exchange State first, because I have a higher Router ID election might be purely based on the higher priority occurs of the master during this process configure master/slave election. Routers are fully Based with eachon the on router adjacent information other. All the router and provided network LSAs are by the DBDs, exchanged and therouters send link-state routers' databases are request packets fully synchronized. Fig. 7. Forming an Adjacencies-Part II (Reference: IPv 6 Essential Pg. 170) DBD contain linkstate advertisement (LSA) headers only and describe the contents of the entire link-state database The neighbor then provides the requested linkstate information in link-state update packets

OSPF – Database Description (DBD) Packet OSPF Packet Type 2 Database Description Packet Database Description fields: I bit = Init bit M bit = More bit MS bit = Master / Slave bit

OSPF – Database Description (DBD) Packet I bit is set to 1 Indicate that this is First DBD packet send by this router 172. 16. 51. 3 This packet contain no data. M bit is set to 1 Indicate that there are more DBD packets to follow MS bit is set to 1 Indicate that this router (172. 16. 51. 3) declares itself to be Master

OSPF – Database Description (DBD) Packet I bit is set to 1 Indicate that this is First DBD packet send by this router 202. 249. 25. 234 This packet contain no data. M bit is set to 1 Indicate that there are more DBD packets to follow MS bit is set to 1 Indicate that this router (202. 249. 25. 234) declares itself to be Master Empty

OSPF – Database Description (DBD) Packet I bit is set to 0 Indicate that this is NOT First DBD packet send by this router 172. 16. 51. 3. It contain database description of router 172. 16. 51. 3 M bit is set to 0 Indicate that there are no more DBD packets to send All database descriptions have been sent MS bit is set to 0 Indicate that this router (172. 16. 51. 3) declares itself to be Slave

OSPF – Database Description (DBD) Packet I bit is set to 0 Indicate that this is NOT First DBD packet send by this router 202. 249. 25. 234 It contain database description of router 202. 249. 25. 234 M bit is set to 1 Indicate that there are more DBD packets to send The database descriptions will still be sent MS bit is set to 1 Indicate that this router (202. 249. 25. 234) is still a Master

OSPF – Database Description (DBD) Packet The router 172. 16. 51. 3 is still sending a empty packet even it had no data description to send. This empty packet I bit is set to 0 is help to keep thethat. DBD sequence number Indicate this is NOT First DBD packet send by this router 172. 16. 51. 3. It contain database description of router 172. 16. 51. 3 matched because router 202. 249. 25. 234 M bit is set to 0 is still sending thethat. DBD Indicate there arepacket. no more DBD packets to send All database descriptions have been sent MS bit is set to 0 Indicate that this router (172. 16. 51. 3) is still a Slave Empty

OSPF – Database Description (DBD) Packet I bit is set to 0 Indicate that this is NOT First DBD packet send by this router 202. 249. 25. 234 It contain database description of router 202. 249. 25. 234 M bit is set to 0 Indicate that there are no more DBD packets to send All database descriptions have been sent MS bit is set to 1 Indicate that this router (202. 249. 25. 234) is still a Master

OSPF – Database Description (DBD) Packet nd e s to e r mo g hin t o he sn t a h o t r. I bit er t e t u is set 0 n o Indicate that this isw. NOT e r h First DBD packet send by this router 172. 16. 51. 3. t o o n b , ter u o Now eis set 0 t er M bit a h t t Indicate that there All g S are no more DBD packets to send g n i d Loa All database descriptions have been sent MS bit is set 0 Indicate that this router (172. 16. 51. 3) is still a Slave Empty

OSPF – Link State Request Packet OSPF Packet Type 2 Link State Request Packet Multiple requests can be sent using a single packet. (Reference IPv 6 Essential pg. 172)

OSPF – Link State Update Packet (0 x 2001) OSPF Packet Type 4 Link State Request Packet Link State Update Packet Type 0 x 2001 Router-LSA

OSPF – Link State Update Packet (0 x 2002) OSPF Packet Type 4 Link State Request Packet Link State Update Packet Type 0 x 2002 Network-LSA

OSPF – Link State Update Packet (0 x 4005) OSPF Packet Type 4 Link State Request Packet Link State Update Packet Type 0 x 4005 AS-External-LSA

OSPF – Link State Update Packet (0 x 0008) OSPF Packet Type 4 Link State Request Packet Link State Update Packet Type 0 x 0008 Link-LSA Purpose: List all IPv 6 Prefix attached to the link

OSPF – Link State Update Packet (0 x 2009) be t s u m t es u q Re t y b e e t d k a c pd ledge a U P ink know OSPF Packet Type 4 ent L h Link State Requestm Ac Eac dg Packet te a t S k n Li d e l w o n Ack Link State Update Packet Type 0 x 2009 Intra-Prefix-LSA

OSPF – Link State Acknowledgement Packet the r e ent ow n r e g ute t n o i r a d t S en ive the s l l l A Fu et is sti ency al OSPF Packet Type 5 ack adjac. Link State Acknowledgement Packet p e lo Hel eep th to k

Learn how to see the above processes using ospfd, and ospf 6 d.

Example: OSPF Interface Information This command shows the interface configuration parameter such as costs, priority, DR/BDR for this interface, and Status.

Example: Neighbours This command shows all neighbors connected to the node and their status.

Example: Link State Database The type of LSA can be specify from the command these is the 8 types of the LSA packet.

Example: Link State Database (cont) This is the LSA database summary.

Example: Link State Information

Example: Shortest Path Tree This is the SPF Tree information. The SPF tree is used to calculate the shortest path from each node to all other nodes in the area.

OSPF 6 D - Troubleshooting

Case 1 : Unable telnet to OSPF Where is ospf 6 d process? The telnet to OSPF failed because the process of OSPF 6 D was not running

Case 1 : Successfully Telnet to OSPF ospf 6 d process The telnet to OSPF success because the process of OSPF 6 D was running

Case 2: Unable to enter Full State with DR in OSPF Changing the rl 0 MTU size to be 1500 bytes for OSPF 6 D

Case 2: Unable to enter Full State with DR in OSPF Adjacency always stay at Ex. Start State and will never proceed to Full State

Case 2: Unable to enter Full State with DR in OSPF From the ospf 6 d. log file, we can see that the adjacency with DR was stuck at Exstart State

Case 2: Successfully to enter Full State with DR Changing the rl 0 MTU size to be 1452 bytes for OSPF 6 D

Case 2: Successfully to enter Full State with DR From the ospf 6 d. log we can see that now the adjacency between this router and DR can proceed till Full State

Case 2: Successfully to enter Full State with DR Now it can proceed till Full State

Case 3 : Router 172. 16. 51. 3 DOWN The 172. 16. 51. 3 doesn’t send Hello packet, the router Dead Timer was counting down. Router Dead Timer for 172. 16. 51. 3 was times up. This router was wiped out from neighbors list

Case 4 : Router 172. 16. 51. 3 UP The 172. 16. 51. 3 send Hello packet, and received by this router. Adjacency between this 2 router running again. Due to the parameter configuration of this 2 router, both don’t want to be DR/BDR, thus they stay at Twoway/DRother state

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