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Alcatel-Lucent Routing Protocols. Module 1 — Introduction Module 2 — Static Routing and Default Routes Module 3 — Routing Information Protocol Module 4 – Link-State Protocols Module 5 — Open Shortest Path First Module 6 — Intermediate System–to–Intermediate System

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Alcatel lucent routing protocols

Alcatel-Lucent Routing Protocols

Module 1— Introduction

Module 2 — Static Routing and Default Routes

Module 3 — Routing Information Protocol

Module 4 – Link-State Protocols

Module 5 — Open Shortest Path First

Module 6 — Intermediate System–to–Intermediate System

Module 7 — Border Gateway Protocol


Alcatel lucent routing protocols1

Alcatel-Lucent Routing Protocols

Module 1— Introduction


Ip addressing basic subnetting

IP Addressing — Basic Subnetting

  • Subnetting allows a network to be subdivided into smaller networks with routing between them.

  • With basic subnetting, each segment uses the same subnet mask.

    • Potential for wasting IP addresses on links that do not require high client density

    • Easiest to implement

    • Required for classful routing protocols

  • VLSM allows the use of different subnet masks for different parts of the network.


Ip addressing vlsm

IP Addressing — VLSM

  • Different subnet masks per network

  • Routing protocols must advertise the subnet mask with updates

  • More efficient use of IP addressing than basic subnetting

  • Requires a good understanding of subnetting

  • RFC 1878 defines VLSM

  • Routing protocols that support VLSM are:

    • RIPv2

    • OSPF

    • IS-IS

    • BGP


Ip addressing review

Network

Network

Network

Multicast

Host

Network

Multicast

Network

Network

Host

Multicast

Host

Host

Multicast

Host

Host

IP Addressing Review

  • IP addresses are broken into classes: A, B, C, and D

Class A: 255.0.0.0 or /8

Class B: 255.255.0.0 or /16

Class C: 255.255.255.0 or /24

Class D: 255.255.255.255 or /32


Section objectives

Section Objectives

  • Introduction to IP routing

    • Review of IP forwarding

    • Control plane vs. data plane functions

    • Common layer 3 routing protocols

      • Distance vector

      • Link state

    • Classful and classless addressing

    • Variable length subnet masking

    • Classless interdomain routing

    • Private IP addresses

    • Network address translation (NAT/PAT)


Movement of data

Source

Dest.

S

D

F

C

S

Data

1.1.1.2

2.2.2.2

A

B

Source

Dest.

WAN

F

C

S

Data

1.1.1.2

2.2.2.2

PPP

Source

Dest.

S

D

F

C

S

Data

1.1.1.2

2.2.2.2

C

D

Movement of Data

2.2.2.2

1.1.1.2

(MAC address = A)

(MAC address = D)

2.2.2.1

1.1.1.1

(MAC address = C)

(MAC address = B)

3.3.3.2

3.3.3.1


Packet forwarding

Packet Forwarding

  • When a router receives a packet, it:

    • Compares the destination IP address of the packet to the FIB

    • Looks for the longest (most specific) match

  • If no match is found, the packet is dropped.

  • If the packet is to be forwarded, the next hop and egress interface must be known.

  • If a match is found, the packet is sent to the next-hop address via the interface specified in the FIB.

    • The next-hop is the next router in the path toward the destination.

    • The egress interface is required for encapsulation.


Common ip routing protocols

Common IP Routing Protocols

  • Legacy routing protocols:

    • RIP version 1

    • RIP version 2

  • Modern routing protocols:

    • OSPF

    • IS-IS

    • BGP


Distance vector protocols

Distance Vector Protocols

  • Distance = How far away

  • Vector = What direction (interface)

  • RIPv1, RIPv2, and BGP are distance vector protocols

Int 1/1/2

IP – 1.1.1.1

Int 1/1/2

IP – 2.2.2.1

Int 1/1/1

Int 1/1/1

IP – 3.3.3.2

IP – 3.3.3.1

Routing Table:

1.1.1.0 – Direct 1/1/2

3.3.3.0 – Direct 1/1/1

2.2.2.0 – 1 hop via 1/1/1

Routing Table:

2.2.2.0 – Direct 1/1/2

3.3.3.0 – Direct 1/1/1

1.1.1.0 – 1 hop via 1/1/1


Link state protocols

Link-State Protocols

  • Link = An interface

  • State = Active or inactive interface

  • OSPF and IS-IS are link-state protocols

  • More complex than distance vector

  • Faster convergence

  • Triggered updates

  • Three databases:

    • Adjacency — Neighbor database

    • Topology — Link-state database

    • Routing — Forwarding database


Link state protocols continued

Link-State Protocols (continued)

  • Adjacency database

  • Link-state database

  • Forwarding database

RTR - C

Network

2.2.2.0/24

1/1/2

RTR - A

RTR - B

1/1/1

Adjacency Database

RTR-B – on 1/1/1

RTR-C – on 1/1/2

2.2.2.0/24

– via 1/1/1 cost 20

– via 1/1/2 cost 40

LSDB

Routing Table:

2.2.2.0/24 – via 1/1/1


Routing table management

OSPF

RIB

RIP

RIB

RTM

Routing Table Management

  • Each routing protocol populates its routes into its RIB.

  • Each protocol independently selects its best routes based on the lowest metric.

  • The best routes from each protocol are sent to the RTM.


Preference

FIB

RIP

RIB

OSPF

RIB

BGP

RIB

Preference

  • The RTM may have a best route from multiple protocols.

  • Selection is based on lowest preference value.

  • The RTM sends its best route to the FIB.

  • This route is the active route and is used for forwarding.

OSPF

RTM

OSPF

BGP


Default preference table

Default Preference Table


Ip addressing classful and classless

IP Addressing — Classful and Classless

Classful

12.1.0.0/16

10.1.1.0/24

10.0.0.0

10.1.1.0

Routing Table:

12.1.0.0 – direct 1/1/2

192.1.1.0 – direct 1/1/1

10.0.0.0 – 1 hop via 1/1/1

10.1.2.0/24

192.1.1.0/24

Classless

10.1.1.0/24

10.1.2.0/24

12.1.0.0/16

10.1.1.0/24

10.1.1.0/24

Routing Table:

12.1.0.0/16 – direct 1/1/2

192.1.1.0 /24 – direct 1/1/1

10.1.1.0/24 – 2 hops via 1/1/1

10.1.2.0/24 – 1 hop via 1/1/1

10.1.2.0/24

192.1.1.0/24


Ip addressing vlsm1

IP Addressing — VLSM

  • Different subnet masks per network

  • Routing protocols must advertise the subnet mask with updates.

  • High-order bits are not reusable.

  • Routing decisions are made based on the longest match.

  • A more efficient use of IP addressing than basic subnetting

  • Requires a good understanding of subnetting

  • RFC 1878 defines VLSM.

  • Routing protocols that support VLSM are:

    • RIPv2

    • OSPF

    • IS-IS

    • BGP


Ip addressing vlsm example

IP Addressing — VLSM Example

172.16.0.0 – 10101100.00010000.00000000.00000000 – Reserved for WAN segments

172.16.1.0 – 10101100.00010000.00000001.hhhhhhhh – First Ethernet segment

….

172.16.254.0 – 10101100.00010000.11111110.hhhhhhhh – Last Ethernet segment

255.255.255.0 – 11111111.11111111.11111111.00000000 – Ethernet mask

172.16.0.4 – 10101100.00010000.00000000.000001 hh – First WAN segment

172.16.0.252 – 10101100.00010000.00000000.111111 hh – Last WAN segment

255.255.255.252 – 11111111.11111111.11111111.111111 00 – WAN mask


Alcatel lucent routing protocols2

Alcatel-Lucent Routing Protocols

Module 2 — Static Routing and Default Routes


What a router needs to know

Routers need to know where networks are located and how best to access them.

This can be accomplished statically with administrative commands.

What a Router Needs to Know

1.1.1.0/24

2.2.2.0/24

1.1.1.1

2.2.2.1

R1

R2

3.3.3.0/30

3.3.3.2

3.3.3.1

Routing Table:

1.1.1.0/24 – Direct

3.3.3.0/30 – Direct

2.2.2.0/24 – static via 3.3.3.2

Routing Table:

2.2.2.0/24 – Direct

3.3.3.0/30 – Direct

1.1.1.0/24 – static via 3.3.3.1


Static routes basic static routes

Static Routes — Basic Static Routes

static-route 0.0.0.0/0 next-hop 3.3.3.1

2.2.2.0/24

R1

R2

Corporate

Headquarters

3.3.3.2

3.3.3.1

static-route 2.2.2.0/24 next-hop 3.3.3.2

  • Configuration of static routes between stub networks and corporate locations


Static routes configuration example

Static Routes — Configuration Example

2.2.2.0/24

R1

R2

Corporate

Headquarters

3.3.3.2

3.3.3.1

config>router> static-route 2.2.2.0/24 next-hop 3.3.3.2

config>router> static-route 0.0.0.0/0 next-hop 3.3.3.1


Default routes basic default route

Default Routes — Basic Default Route

2.2.2.0/24

R1

R2

Corporate

Headquarters

3.3.3.1

3.3.3.2

R2# show router route-table

============================================================================

Route Table

============================================================================

Dest Address Next Hop Type Protocol Age Metric Pref

----------------------------------------------------------------------------

3.3.3.0/24System Local Local01d02h 00

2.2.2.0/24 System Local Local 08d03h 0 0

0.0.0.0/0 3.3.3.1 Remote Static 01d02h 1 5

----------------------------------------------------------------------------


Static routes floating static routes

Static Routes — Floating Static Routes

Backup

2.2.2.0/24

1.1.1.2

1.1.1.1

R1

R2

Corporate

Headquarters

Primary path

3.3.3.2

3.3.3.1

config>router> static-route 2.2.2.0/24 next-hop 3.3.3.2

config>router> static-route 2.2.2.0/24 next-hop 1.1.1.2 preference 200

  • Configuration of a floating static route between stub networks and corporate locations


Static route verification show command

Static Route Verification — Show Command

  • The command below shows static routes configured in the routing table.

Context:show>router>

Syntax: static-route [[ip-prefix [/mask]] | [preference preference] | [next-hop ip-addr] | tag tag

Example:R1# show router route-table protocol static

==============================================================================

Route Table (Router: Base)

==============================================================================

Dest AddressNext Hop Type Proto Age Metric Pref

-------------------------------------------------------------------------------

2.2.2.0/24 3.3.3.2 Remote Static 00h01m34s 1 5

2.2.2.0/241.1.1.2 Remote Static 00h01m15s 1 200

-------------------------------------------------------------------------------

No. of Routes: 1

==============================================================================


Static route verification show command continued

Static Route Verification — Show Command (continued)

2.2.2.0/24

R1

R2

Corporate

Headquarters

3.3.3.2

3.3.3.1

R1# show router route-table 2.2.2.0/24

==============================================================================

Route Table (Router: Base)

===============================================================================

Dest Address Next Hop Type Proto Age Metric Pref

-------------------------------------------------------------------------------

2.2.2.0/24 3.3.3.2 Remote Static 00h02m54s 1 5

-------------------------------------------------------------------------------

No. of Routes: 1

==============================================================================


Static routes ping command

Static Routes — Ping Command

2.2.2.2

2.2.2.0/24

3.3.3.2

3.3.3.1

Corporate

Headquarters

R1# ping 2.2.2.2 detail

PING 2.2.2.2: 56 data bytes

64 bytes from 2.2.2.2 via fei0: icmp_seq=0 ttl=64 time=0.000 ms.

64 bytes from 2.2.2.2 via fei0: icmp_seq=1 ttl=64 time=0.000 ms.

64 bytes from 2.2.2.2 via fei0: icmp_seq=2 ttl=64 time=0.000 ms.

64 bytes from 2.2.2.2 via fei0: icmp_seq=3 ttl=64 time=0.000 ms.

64 bytes from 2.2.2.2 via fei0: icmp_seq=4 ttl=64 time=0.000 ms.

---- 2.2.2.2 PING Statistics ----

5 packets transmitted, 5 packets received, 0.00% packet loss

round-trip min/avg/max/stddev = 0.000/0.000/0.000/0.000 ms

R1#


Static routes traceroute command

Static Routes — Traceroute Command

2.2.2.2

2.2.2.0/24

R1

R2

Corporate

Headquarters

3.3.3.2

3.3.3.1

R1# traceroute 2.2.2.2

traceroute to 2.2.2.2, 30 hops max, 40 byte packets

1 3.3.3.2 <10 ms <10 ms <10 ms

2 2.2.2.2 <10 ms <10 ms <10 ms


Learning assessment

Learning Assessment

  • Do static routes have a higher or lower preference value than dynamic routes?

  • What is the command syntax to create a static route in the 7750 SR?

  • A router has a default route, a static route to 10.10.8.0/24, and a route to 10.8.0.0/14 learned from RIP. Which route is used for a packet with destination address 10.10.10.10?


Alcatel lucent routing protocols3

Alcatel-Lucent Routing Protocols

Module 3 — Routing Information Protocol


Section objectives1

Section Objectives

  • Distance vector overview

    • Split horizon

    • Route poisoning

    • Poison reverse

    • Hold-down timers


Distance vector overview

Distance Vector Overview

  • Routers send periodic updates to physically adjacent neighbors

  • Updates contain the distance (how far) and vectors (direction) for networks

RTR-B

RTR-A

100 Mb/s

1 Gb/s

1 Gb/s

1 Gb/s

RTR-C

RTR-D


Distance vector overview continued

Distance Vector Overview (continued)

  • The router processes and compares the information contained in the routing update received with what is in its routing table.

Process

and compare

with routing

table

Periodic update

Sent to neighbor

routers

Update from neighbor


Split horizon

Split Horizon

  • An adjacent router does not advertise networks back to the source of the network information.

10.0.0.0

10.0.0.0 – 2 hops

10.0.0.0 – 1 hop

X

RTR-A

RTR-B

RTR-C

Routing Table:

10.0.0.0 – 2 hops

via 1/1/1

Routing Table:

10.0.0.0 – 1 hop

via 1/1/1

Routing Table:

10.0.0.0 – 0 hops

via 1/1/1


Route poisoning

Route Poisoning

  • When a network goes away, the sourcing router sets the hop value to infinity and sends a triggered update to its neighbors.

10.0.0.0

10.0.0.0 – 16 hops

10.0.0.0 – 16 hops

X

RTR-A

RTR-B

RTR-C

Routing Table:

10.0.0.0 – 16 hops

via 1/1/1

Routing Table:

10.0.0.0 – 16 hops

via 1/1/1

Routing Table:

10.0.0.0 – 16 hops

via 1/1/1

Routing Table:

10.0.0.0 – 2 hops

via 1/1/1

Routing Table:

10.0.0.0 – 1 hop

via 1/1/1

Routing Table:

10.0.0.0 – 0 hops

via 1/1/1


Poison reverse

Poison Reverse

  • Poison reverse is the only time that split horizon is violated. This helps to avoid loop creation when a network fails.

10.0.0.0 — 16 hops

Poison reverse

10.0.0.0 — 16 hops

Poison reverse

10.0.0.0 — 16 hops

10.0.0.0 — 16 hops

10.0.0.0

X

RTR-A

RTR-B

RTR-C

Routing Table:

10.0.0.0 — 16 hops

via 1/1/1

Routing Table:

10.0.0.0 — 16 hops

via 1/1/1

Routing Table:

10.0.0.0 — 16 hops

via 1/1/1

Routing Table:

10.0.0.0 — 2 hops

via 1/1/1

Routing Table:

10.0.0.0 — 1 hop

via 1/1/1

Routing Table:

10.0.0.0 — 0 hops

via 1/1/1


Hold down timers

Hold-Down Timers

  • Hold-down timers provide time for other routers to converge and reduce loops from being created when a network fails.

10.0.0.0

10.0.0.0 — 16 hops

10.0.0.0 — 16 hops

X

RTR-A

RTR-B

RTR-C

Routing Table:

10.0.0.0 — 1 hop

via 1/1/1

Routing Table:

10.0.0.0 — 0 hops

via 1/1/1

Routing Table:

10.0.0.0 – 16 hop –

Via 1/1/1

Routing Table:

10.0.0.0 – 16 hop –

Via 1/1/0

Routing Table:

10.0.0.0 – 16 hop –

Via 1/1/1

Routing Table:

10.0.0.0 — 2 hops

via 1/1/1

Hold-down timer

180 seconds

Hold-down timer

180 seconds

Hold-down timer

180 seconds


Combined loop avoidance techniques

Combined Loop Avoidance Techniques

  • Combined, all attributes function as follows:

10.0.0.0 — 16 hops

Poison reverse

10.0.0.0 — 16 hops

Poison reverse

10.0.0.0 — 16 hops

10.0.0.0 — 16 hops

10.0.0.0

X

RTR-A

RTR-B

RTR-C

Routing Table:

10.0.0.0 — 1 hop

via 1/1/1

Routing Table:

10.0.0.0 — 0 hops

via 1/1/1

Routing Table:

10.0.0.0 – 16 hop –

Via 1/1/0

Routing Table:

10.0.0.0 – 16 hop –

Via 1/1/1

Routing Table:

10.0.0.0 – 16 hop –

Via 1/1/0

Routing Table:

10.0.0.0 — 2 hops

via 1/1/1

Hold-down timer

180 seconds

Hold-down timer

180 seconds

Hold-down timer

180 seconds


Rip overview

RIP Overview

  • Uses a hop-count metric

  • Sends updates of the routing table to neighbors

  • Maximum of 15 hops; 16 hops equals infinity

  • 30-second advertisement interval by default

  • Authentication is available in RIPv2

  • VLSM is supported by RIPv2


Rip overview continued

RIP Overview (continued)

100 Mb/s

RTR-B

RTR-A

1 Gb/s

1 Gb/s

1 Gb/s

RTR-C

RTR-D


Ripv1 vs ripv2

RIPv1 vs. RIPv2


Rip major component configuration

RIP – Major Component Configuration

  • Router

    • Interface (assumed to be already complete)

    • Route policies

  • RIP

    • Group

    • Neighbor


Alcatel lucent routing protocols4

Alcatel-Lucent Routing Protocols

Module 4 – Link-State Protocols


Distance vector vs link state

Distance Vector vs. Link State

Distance vector

Link state

  • Views the network topology

    from the neighbor’s

    perspective

  • Adds distance vectors

    from router to router

  • Frequent, periodic updates:

    slow convergence

  • Passes copies of the routing

    table to neighbor routers

  • Has a common view of the

    entire network topology

  • Calculates the shortest

    path to other routers

  • Event-triggered updates:

    faster convergence

  • Passes link-state routing

    updates to other routers


Link state overview

Link State Overview

Link state-driven updates, periodic hellos

Classless routing protocol

Sends subnet mask in update

Supports VLSM, CIDR, and manual route summarization

Supports authentication

Maintains multiple databases

Sends updates using multicast addressing


Link state overview continued

Link State Overview (continued)

  • Link = An interface

  • State = Active or inactive interface, cost

  • IS-IS and OSPF are link-state protocols

  • More complex than distance vector

  • Faster convergence

  • Triggered updates

  • Three databases:

    • Adjacency – neighbor database

    • Topology – link-state database

    • Routing – forwarding database


Link state overview continued1

Link State Overview (continued)

  • Adjacency database

  • Link-state database

  • Forwarding database

RTR - C

Network

2.2.2.0/24

1/1/1

1/1/2

RTR - A

RTR - B

Adjacency database

RTR-B – on 1/1/2

RTR-C – on 1/1/1

2.2.2.0/24

via 1/1/2 cost 20

via 1/1/1 cost 40

LSDB

Routing table

2.2.2.0/24 via 1/1/2


Link state overview continued2

Link State Overview (continued)

2.2.2.0/30

10.0.0.0/8

.1

.2

.2

Step 1 – Updates received

from peers

.1

3.3.3.0/30

Routing table

10.0.0.0/8 via 2.2.2.1

Step 2 – Topology database

created

Step 3 – SPF algorithm

determines the best

path to destination networks

10.0.0.0/8

Via 2.2.2.1 Cost 10

Via 3.3.3.1 Cost 20

Step 4 – Routing

table created

10.0.0.0/8

Via 2.2.2.1 Cost 10 – BEST

Via 3.3.3.1 Cost 20


Exchanging link state information

R3 Link-state packet

R1 Link-state packet

R2 Link-state packet

B

C

A

10

10

10

C

D

B

10

10

10

Exchanging Link-State Information

R1

R2

R3

B

C

D

A

Routers exchange LSPs with each other. Each begins with directly connected networks for which it has direct link-state information.


Building a topological database

R3 Link-state packet

R3 Link-state packet

R2 Link-state packet

R1 Link-state packet

R2 Link-state packet

R2 Link-state packet

R1 Link-state packet

R1 Link-state packet

R3 Link-state packet

C

B

C

A

A

B

C

A

B

10

10

10

10

10

10

10

10

10

B

D

B

C

C

D

D

B

C

10

10

10

10

10

10

10

10

10

Building a Topological Database

R1

R2

R3

B

C

D

A


Calculating the spf tree and populating the routing table

R1 Link-state packet

R2 Link-state packet

R3 Link-state packet

A

C

B

10

10

10

D

B

C

10

10

10

1

2

3

Calculating the SPF Tree and Populating the Routing Table

R1

R2

R3

B

C

D

A

SPF

SPF tree

R1

Routing

table


Spf algorithm

SPF Algorithm

R3

10

10.0.0.0/8 (net1)

100

R1

5

R2


Spf algorithm continued

SPF Algorithm (continued)

R3

10

10.0.0.0/8 (net1)

100

R1

5

R2


Link state topology change

Link State – Topology Change

  • Link-state updates are driven by topology changes.

Run SPF

Update

routing

table

Topology

change

Run SPF

Update

routing

table

Run SPF

Update

routing

table

Link-state information


Sequence numbers

Sequence Numbers

  • Sequence numbers must be included in the link-state information.

    • Without sequence numbers, the link-state information could be flooded indefinitely.

    • The sequence number remains the same, router-to-router, during the flooding process.

  • In a link-state environment, routers use the sequence numbers for the following decisions when they receive link-state updates:

    • If the sequence number is lower than the one in the database, the link-state information is discarded.

    • If the sequence number is the same as the one in the database, an ACK is sent. The link-state information is then discarded.

    • If the sequence number is higher, the link-state information is populated in the topological database, an ACK is sent, and the link-state information is forwarded to its neighbors.


Sequence numbers continued

Sequence Numbers (continued)

R1

R2

R3

B

C

D

A

R1 Link-state packet

R1 Link-state packet

R1 Link-state packet

Seq=1

Seq=2

Seq=1

R1

R2

R3

B

C

D

A

R1 Link-state packet

R1 Link-state packet

R1 Link-state packet

Seq=2

Seq=2

Seq=1


Sequence numbers continued1

Sequence Numbers (continued)

  • R1 receives 2 copies of the link-state information for network Z.

    • R1 must decide what to do with the second copy of the link-state information it receives.

R1

R2

R3

B

C

Cost 10

Cost 10

A

Cost 10

Cost 10

D

F

E

Z

Cost 20

Cost 20

R6

R5

R4


Link state information aging

Link-State Information Aging

  • Link-state information includes an age field.

    • The age of newly created link-state information is set to 0 for OSPF and 1200 for IS-IS. It is incremented by every hop during the flooding procedure for OSPF and is decremented for IS-IS. The link-state age is also incremented for OSPF and decremented for IS-IS as it is held in the topological database.

  • Maximum age

    • When the link-state information reaches its maximum age, it is no longer used for routing. The link-state information is flooded to the neighbors with the maximum age, and the link-state information is removed from the topological database.


Is is packet processing

IS-IS – Packet Processing

  • A router deals with topology changes as follows:

Sequence No.

same?

Is entry in

LSDB?

Yes

Yes

LSU/LSA

Ignore

No

No

Add to LSDB

Is sequence

number higher

than one in

LSDB?

Send ACK

Yes

No

Flood LSA

Send LSU back

with newer

information

Run SPF

End


Hierarchy in link state networks

Hierarchy in Link-State Networks

  • Scalability issues exist for link-state networks:

    • The size of the link-state database increases exponentially with the size of the network.

    • The complexity of the SPF calculation also increases exponentially.

    • A topology change requires complete recalculation of the forwarding table on every router.

  • Hierarchy allows a large routing domain to be split into several smaller routing domains.

  • IS-IS and OSPF both implement hierarchy but use different techniques.

  • Hierarchy results in suboptimal routing.

  • Hierarchy is less common than in the past due to the increased capacity of routers.


Is is hierarchical view

IS-IS – Hierarchical View

Integrated IS-IS Network

L1

L2

Area 2

L1/L2

L1

L1/L2

Area 3

L1/L2

Backbone (Level 2) links

Level 1 links

L1 Level 1

L2 Level 2

L1/L2 Level 1/Level 2

L1

Area 1


Ospf hierarchical view continued

OSPF – Hierarchical View (continued)

OSPF Hierarchical Routing

Area 0.0.0.0

Area 0.0.0.2

Area 0.0.0.1


Alcatel lucent routing protocols5

Alcatel-Lucent Routing Protocols

Module 5 — Open Shortest Path First


Ospf rfc history

1987

1989

1991

1994

1997

1998

1999

Present

OSPF — RFC History

OSPF v1

RFC 1131

defined

OSPF

workgroup

formed

OSPF v2

Updated

RFC 1583

OSPF v2

RFC 1247

defined

OSPF v2

Updated

RFC 2328

OSPF v2

Updated

RFC 2178

OSPF for

IPv6

RFC 2740

OSPF

work in

progress


Ospf protocol overview

OSPF — Protocol Overview

Link state-driven updates, periodic hellos

Classless routing protocol

Subnet mask sent in update

Support for VLSM, CIDR, and manual route summarization

Support for authentication

Maintenance of multiple databases

Multicast addressing – 224.0.0.5 and 224.0.0.6


Ospf key features

OSPF — Key Features

  • Key OSPF features are:

    • Backbone areas

    • Stub areas

    • NSSAs

    • Virtual links

    • Authentication

    • Support for VLSM and CIDR

    • Route redistribution

    • Routing interface parameters

    • OSPF-TE extensions


Ospf protocol comparison

OSPF — Protocol Comparison

Feature

RIPv2

IS-IS

OSPF

Updates

Periodic

Incremental

Incremental

Update type

Broadcast/Multicast

L2 Multicast

L3 Multicast

Transport

UDP

Layer 2

IP

Authentication

Simple and MD5

Simple and MD5

Simple and MD5

Metric

Hops

Cost

Cost

Metric type

Distance vector

Link-state

Link-state

VLSM / CIDR support

Yes

Yes

Yes

Topology size

Small/Medium

Large

Large

Convergence

Slow

Fast

Fast


Ospf link state protocol comparison

OSPF — Link-State Protocol Comparison

Feature

IS-IS

OSPF

Updates

Incremental

Incremental

Multicast layer

Layer 2

Layer 3

Authentication

Simple and MD5

Simple and MD5

Metric

Default: all ports cost 10

Auto-calculation on interface

Metric type

Link-state

Link-state

LSA types

L1 and L2

Multiple types

Area hierarchy

Not required

Backbone area

Area boundaries

On segment

At interface

Convergence

Fast

Fast


Ospf path determination

OSPF — Path Determination

  • OSPF uses SPF for path determination.

  • SPF uses cost values to determine the best path to a destination.

RTR-C

10.0.0.0

Cost 125

Cost 125

Cost 0

Cost 10

RTR-A

RTR-B

Cost 125

RTR-A

10.0.0.0 – Cost 260 via RTR C

*10.0.0.0 – Cost 135 via RTR B

* = Best path


Calculating link cost

Calculating Link Cost

  • Cost = reference-bandwidth ÷ bandwidth

  • The default reference-bandwidth is 100 000 000 kb/s or 100 Gb/s.

  • The default auto-cost metrics for various link speeds are as follows:

    • 10-Mb/s link default cost of 10 000

    • 100-Mb/s link default cost of 1000

    • 1-Gb/s link default cost of 100

    • 10-Gb/s link default cost of 10

  • The cost is configurable.


  • Configuration basics

    Configuration Basics

    • Interfaces must be configured in an OSPF area.

      • By default, interfaces in an area are advertised by OSPF.

      • Routes received through OSPF are advertised by OSPF.

      • No other routes are advertised by default.

    • Verify that adjacencies are formed with neighbors.

    • Verify that routes are in the routing table.


    Ospf multicast addressing

    OSPF — Multicast Addressing

    • OSPF uses class D multicast addresses in the range 224.0.0.0 to 239.255.255.255.

    • Specially reserved addresses for OSPF:

      • 224.0.0.5: All routers that speak OSPF on the segment

      • 224.0.0.6: All DR/BDRs on the segment

    • IP multicast addresses use the lower 23 bits of the IP address as the low-order bits of the MAC multicast address 01-005E-XX-XX-XX.

      • 224.0.0.5 = MAC 01-00-5E-00-00-05

      • 224.0.0.6 = MAC 01-00-5E-00-00-06


    Ospf generic packet

    OSPF — Generic Packet

    • OSPF packets use protocol number 89 in the IP header.

    • OSPF is its own transport layer.

    Link header

    IP header

    OSPF packet types

    Link trailer

    IP header protocol

    ID 89 = OSPF


    Opsf packet types

    OPSF — Packet Types

    • OSPF hello

    • OSPF database descriptor

    • OSPF link-state request

    • OSPF link-state update

    • OSPF link-state ACK


    Ospf link topology types

    Multi-access

    OSPF — Link Topology Types

    Point-to-point


    Ospf router id

    OSPF — Router ID

    • Each router must have a router ID, the ID by which the router is known to OSPF.

      • The default RID is the last 32 bits of the chassis MAC address.

      • Configuring a system interface overrides the default.

        • Using a system interface is easier to document.


    Ospf point to point segments

    OSPF — Point-to-Point Segments

    • On point-to-point links, there is no need for a DR or BDR.

    • All packets are sent via IP multicast address 224.0.0.5.

    • Usually a leased-line (i.e., HDLC, PPP) segment

    • Can be configured on point-to-point Ethernets

    RTR - C

    Network

    2.2.2.0/24

    RTR - A

    RTR - B


    Ospf lan communication

    OSPF — LAN Communication

    • Election of the DR and BDR in multi-access networks:

    A

    1.1.1.5

    B

    1.1.1.4

    RTR-B

    Has the second highest

    RID, so it will be the BDR

    RTR-A

    Has the highest

    RID, so it will be

    the DR

    C

    1.1.1.1

    D

    1.1.1.2

    E

    1.1.1.3

    • Each router sends hellos.

    • The router with the highest priority is the DR.

    • If all priorities are the same, the DR is the router with the highest RID.


    Ospf exchanging updates in a lan

    OSPF — Exchanging Updates in a LAN

    • Election of the DR and BDR in multi-access networks:

    RTR-B (BDR)

    1.1.1.4

    RTR-A (DR)

    1.1.1.5

    RTR-A sends update to

    All OSPF routers using

    IP address 224.0.0.5

    RTR-C sends update to

    All DRs using IP address

    224.0.0.6

    RTR-C

    1.1.1.1

    D

    1.1.1.2

    E

    1.1.1.3

    • Routers use the 224.0.0.6 IP address to send updates to the DRs.

    • The BDR monitors the DR to ensure that it sends updates.

    • The DR uses 224.0.0.5 to send updates to all OSPF routers.


    Alcatel lucent routing protocols6

    Alcatel-Lucent Routing Protocols

    Module 6 — Intermediate System–to–Intermediate System


    Is is protocol overview

    IS-IS — Protocol Overview

    • Development began prior to that of OSPF.

    • The U.S. government required ISPs to use IS-IS for early stages of the Internet.

    • IS-IS supports IPv6.

    • Many large enterprise networks and ISPs use IS-IS due to the scalability and stability of the protocol.


    Is is rfc history

    IS-IS — RFC History

    RFC 1142

    Original

    RFC

    1990

    RFC 1195

    TCP/IP

    support

    1990

    ISO 10589

    released

    1992

    1994

    RFC 1629

    NSAP and

    Internet

    …..

    Other IS-IS

    RFCs released

    2002

    Present

    RFC 33509

    TLV

    code points

    IS-IS

    work in

    progress


    Is is protocol overview continued

    IS-IS — Protocol Overview (continued)

    Link-state driven updates, periodic hellos

    Classless routing protocol

    Subnet mask sent in update

    Support for VLSM, CIDR, and manual route summarization

    Support for authentication

    Maintenance of multiple databases

    Layer 2 multicast addressing


    Is is key features

    IS-IS — Key Features

    • Key IS-IS features are:

      • Area hierarchy

      • Authentication

      • Support for VLSM and CIDR

      • Route redistribution

      • Routing interface parameters

      • IS-IS TE extensions


    Is is protocol comparison

    IS-IS — Protocol Comparison

    Feature

    RIPv2

    OSPF

    IS-IS

    Updates

    Periodic

    Incremental

    Incremental

    Update type

    Broadcast/Multicast

    L3 Multicast

    L2 Multicast

    Authentication

    Simple and MD5

    Simple and MD5

    Simple and MD5

    Metric

    Hops

    Cost

    Cost

    Metric type

    Distance vector

    Link-state

    Link-state

    VLSM / CIDR support

    Yes

    Yes

    Yes

    Topology size

    Small

    Very large

    Very large

    Summarization

    Manual

    Manual

    Manual

    Convergence

    Slow

    Fast

    Fast


    Is is link state protocol comparison

    IS-IS — Link-State Protocol Comparison

    Feature

    IS-IS

    OSPF

    Updates

    Incremental

    Incremental

    Multicast layer

    Layer 2

    Layer 3

    Authentication

    Simple and MD5

    Simple and MD5

    Metric

    Default: all ports cost 10

    Auto-calculation on interface

    Metric type

    Link-state

    Link-state

    Update types

    L1 and L2

    Multiple types

    Area hierarchy

    Not required

    Backbone area

    Area boundaries

    On segment

    At interface

    Convergence

    Fast

    Fast


    Is is frequently used terms

    IS-IS — Frequently Used Terms

    • Area — Corresponds to the level 1 subdomain

    • End system — Typically a computer, printer, or other attached device

    • Intermediate system — Router in an IS-IS network

    • Neighbor — A physically adjacent router

    • Adjacency — A separate adjacency is created for each neighbor on a circuit and for each level of routing (level 1 and level 2) on a broadcast circuit.

    • Circuit — A single locally attached network

    • Link — The communication path between 2 neighbors

    • CSNP — Complete sequence number PDU

    • PSNP — Partial sequence number PDU

    • PDU — Protocol data unit


    Is is frequently used terms continued

    IS-IS — Frequently Used Terms (continued)

    • Designated IS — The intermediate system in a LAN that is designated to generate updates on behalf of the nodes in the LAN

    • Pseudo node — When a broadcast subnetwork has n connected intermediate systems, the broadcast subnetwork itself is considered to be a pseudo node.

    • Broadcast subnetwork — A multi-access subnetwork (such as Ethernet) that supports the capability of addressing a group of attached systems with a single PDU

    • General topology subnetwork — A topology that is modeled as a set of point-to-point links, each of which connects 2 systems

    • Routing subdomain — A set of intermediate systems and end systems that are located within the same routing domain

    • Level 2 subdomain — The set of all level 2 intermediate systems in a routing domain


    Is is protocol overview1

    IS-IS — Protocol Overview

    • IS-IS uses SPF for path determination.

    • SPF uses cost values to determine the best path to a destination.

    RTR-C

    10.0.0.0

    Cost: 10

    Cost: 10

    Cost: 10

    Cost: 10

    RTR-A

    RTR-B

    Cost: 10

    RTR-A

    10.0.0.0: cost 30 via RTR-C

    *10.0.0.0: cost 20 via RTR-B

    * = Best path

    Packet flow


    Is is iso network addressing

    IS-IS — ISO Network Addressing

    • IS-IS uses unique addressing (OSI NSAP addresses) compared to that of other IP routing protocols.

    • Each address identifies the area, system, and sector.

      • Routers with common area addresses form L1 adjacencies.

      • Routers with different area addresses form L2 adjacencies, if capable.

    • 2-layer hierarchy:

      • Level 1: Builds the local area topology and forwards traffic to other areas through the nearest L1/L2 router

      • Level 2: Exchanges prefix information and forwards traffic between areas


    Is is iso network addressing continued

    IS-IS — ISO Network Addressing (continued)

    • Layer 2 multicast addressing is implemented to support IS-IS.

    • On Ethernet, the following multicast addresses are reserved:

      • L1 updates use 01-80-C2-00-00-14.

      • L2 updates use 01-80-C2-00-00-15.


    Is is link state overview

    IS-IS — Link-State Overview

    L1

    L2

    Area 49.0002

    L1/L2

    L1

    L1/L2

    Area 49.0003

    Backbone (level 2) link

    Level 1 link

    L1 Level 1

    L2 Level 2

    L1/L2 Level 1/level 2

    L1/L2

    L1

    Area 49.0001


    Is is nsap addressing

    IS-IS — NSAP Addressing

    IDP

    DSP

    IDI

    SEL

    AFI

    High Order-DSP

    System ID

    variable

    6

    1

    Area ID

    System Address

    NSEL

    NSAP — Network service access point

    IDP — Initial domain partDSP — Domain specific part

    AFI — Authority and format indicatorIDI — Initial domain identifier (e.g., 49 is local assigned, binary)

    High Order-DSP — High Order Domain Specific Part

    SEL — N-selector (NSEL)


    Is is protocol characteristics

    IS-IS — Protocol Characteristics

    • ItemValue

      Maximum metric value assignable to a link16 777 215

      Maximum metric value for a path4 261 412 864

      All L1 IS multicast address01-80-C2-00-00-14

      All L2 IS multicast address01-80-C2-00-00-15

      SAP for IS-IS on 802.3 LANsFE

      Protocol discriminator for IS-IS83

      NSAP selector for IS-IS00

      Sequence modulus232

      Size of LSP, which all IS routers must be able to handle1492

      Maximum age1200

      Zero life age60

      Maximum number of area addresses in a single area3


    Is is packet format

    IS-IS — Packet Format

    • IS-IS packets use layer 2 encapsulation of the media.

    • The Ethernet type field is set to 0xFEFE to denote an IS-IS packet instead of an IP packet.

    • The TLV identifies the type of information in the IS-IS packet.

    • IS-IS packets are called PDUs.

    Ethernet header

    Type = 0xFEFE

    IS-IS header

    IS-IS TLV

    Link trailer


    Is is packet format details

    IS-IS — Packet Format Details

    • Ethernet destination address:

      • 01-80-C2-00-00-14 – L1 updates

      • 01-80-C2-00-00-15 – L2 updates

    • Ethernet source address: source router interface MAC address

    • 802.3 LLC DSAP and SSAP = FE:FE

    • Layer 3 protocol discriminator: 83

    Ethernet header

    Type = 0xFEFE

    IS-IS header

    IS-IS TLV

    Link trailer


    Is is packet format details continued

    IS-IS — Packet Format Details (continued)

    • IS-IS sends PDUs.

    • PDUs are encapsulated directly into the layer 2 frame.

    • There are 4 types of PDUs:

      • Hello (ESH, ISH, and IIH) — Maintain adjacencies

      • LSP (link-state packet) — Information about neighbors and links, generated by all L1 and L2 routers

      • PSNP (Partial Sequence Number PDU) — Specific requests and responses about links, generated by all L1 and L2 routers

      • CSNP — Complete list of LSPs exchanged to maintain database consistency


    Alcatel lucent routing protocol s

    Alcatel-Lucent Routing Protocols

    Module 7 — Border Gateway Protocol


    Bgp scope

    BGP Scope

    • Enables the exchange of routing information between autonomous systems (AS)

    • An AS is a collection of routers that are under a single administration, which presents a consistent routing policy.

    • Enables the implementation of administrative policies

    • BGP has already scaled to:

      • Large number of ASs

      • Large number of neighbors

      • Large volume of table entries

      • High rate of change


    Autonomous systems in bgp

    Autonomous Systems in BGP

    AS-65002

    AS-65003

    An AS is a group of networks and network equipment under a common administration.

    IGP protocols such as OSPF, IS-IS, and RIP run in an AS.

    BGP is used to connect ASs.

    AS-65001


    Autonomous systems in bgp continued

    Autonomous Systems in BGP (continued)

    • Public autonomous systems:

      • Assigned by ARIN or another authority

      • Must be used when connecting to other ASs on the Internet.

      • Range from 0 to 64 511

    • Private autonomous systems:

      • Assigned by ISPs (for some clients) and local administrators

      • Not allowed to be advertised to other ISPs or on the Internet

      • Range from 64 512 to 65 535


    Bgp features

    BGP Features

    • Path vector protocol:

      • Neighbor is any reachable device

      • Unicast exchange of information

      • Reliability using TCP

      • Uses well-known TCP port 179

      • Periodic keepalive for session management

      • Event-driven

      • Robust metrics

      • Authentication

    • Similar behavior as other TCP/IP applications

    • Because BGP peers are not always directly connected, BGP relies on IGP to route between peers.


    Ebgp vs ibgp overview

    eBGP vs. iBGP Overview

    • 2 types of BGP sessions are possible.

    • The routers may be in different ASs:

      • Called external BGP or eBGP

      • Typically directly connected, but not mandatory

      • Different administrations

    • The routers may be in the same AS:

      • Called internal BGP or iBGP

      • Typically remote, but could be directly connected

      • Same administration


    Alcatel lucent routing protocols

    www.alcatel-lucent.com


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