RIP and OSPF Training Document.pdf

37
All Rights Reserved © Alcatel-Lucent 2006, ##### RIP and OSPF Training Sakila Balasubramaniam

Transcript of RIP and OSPF Training Document.pdf

Page 1: RIP and OSPF Training Document.pdf

All Rights Reserved © Alcatel-Lucent 2006, #####

RIP and OSPF Training

Sakila Balasubramaniam

Page 2: RIP and OSPF Training Document.pdf

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Types of Routing

Routing protocols ate classified into two types:

Static Routing:

A method to configure routing information in each router.

Advantage:

Able to provide stable arrival of the network

Dynamic Routing:

A method that router learns routing information automatically.

Advantage:

Able to change route in response to the condition of network.

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VRF

Fast-Path VRF :

Ø IP forwarding takes place in hardware level.

Ø RIP and OSPF can be enabled only on fast-path VRF .

Ø Number of Fast-path VRFs depends on the capability of BCM chips.

Slow-path VRF:

Ø IP forwarding is done by the software

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Interior gateway protocol

Routing protocols that are used within an autonomous system

Two types:

Distance-vector routing Protocols- Each router does not possess information about the full network topology. It advertises its distances from other routers and receives similar advertisements from other routers.

1. Routing Information Protocol (RIP)

2. Interior Gateway Routing Protocol (IGRP)

Link-state routing protocols- Each node possesses information about the complete network topology. Each node then independently calculates the best next hop from it for every possible destination in the network using local information of the topology.

1. Open Shortest Path First (OSPF)

2. Intermediate system to intermediate system (IS-IS)

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Routing Information Protocol (RIP)

RIP:Algorithm used is Bellman-Ford algorithm

RIP uses UDP port 520 for route updates. RIP calculates the best route based on hop count.Maximum 512 bytes.

Administrative distance for RIPv2 is 120.

RIP-1:RIPV1 messages are broadcast.

Features:

o No authentication.

o Auto-summarization of routes.

o Doesn’t support VLSM. RIPv1 is difficult to use with supernetting. All CIDR supernetsmust be exploded and advertised to RIPv1 as individual "natural" classfuladvertisements.

Class A –255.0.0, Class B-255.255.0.0, class C-255.255.255.0

RIP-V1Compatibility: RIP-2 messages are broadcast.

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Routing Information Protocol (RIP)

RIPV2 :RIP-2 messages are multicast.Multicast address:224.0.0.9

Features:

o Carries a subnet mask.

o Supports password authentication security.

o Specifies the next hop address.

o Does not require that routes be aggregated on the network boundary

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RIP V1 format

IP header UDP header RIP Message

Command Version Set to 00...0

32-bit address

Unused (Set to 00...0)

address family Set to 00.00

Unused (Set to 00...0)

metric (1-16)

one

rout

e en

try

(20

byte

s)

Up to 24 more routes (each 20 bytes)

32 bits

1: request2: response

2: for IP0…0: request full rou-ting table

1: RIPv1

Address of destination

Cost (measured in hops)

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RIPV1 Packet

• Command—Indicates whether the packet is a request or a response.

• Version number—Specifies the RIP version used. This field can signal different potentially incompatible versions.

• Zero—This field is not actually used. It was added solely to provide backward compatibility with pre-standard varieties of RIP. Its name comes from its defaulted value: zero.

• Address-family identifier (AFI)—Specifies the address family used. RIP is designed to carry routing information for several different protocols.

• Address—Specifies the IP address for the entry.

• Metric—Indicates how many internet work hops (routers) have been traversed in the trip to the destination. This value is between 1 and 15 for a valid route, or 16 for an unreachable route.

Note Up to 25 occurrences of the AFI, Address, and Metric fields are permitted in a single IP RIP packet. (Up to 25 destinations can be listed in a single RIP packet.)

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RIP V2 Packet Format

0RIPv2 packet with no AuthenticationRIPv2 packet with no Authentication RIPv2 packet with AuthenticationRIPv2 packet with Authentication

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RIP V2 Packet Format

• Command—Indicates whether the packet is a request or a response.

• Version—Specifies the RIP version used. In a RIP packet implementing any of the RIP 2 fields or using authentication, this value is set to 2.

• Route Domain—Has a value set to zero by default. The RD is needed to allow multiple, independent RIP "clouds" to co- exist on the same physical wire.

• Address-family identifier (AFI)—Specifies the address family used. RIPv2's AFI field functions identically to RFC 1058 RIP's AFI field, with one exception: If the AFI for the first entry in the message is 0xFFFF, the remainder of the entry contains authentication information.

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RIP V2

Route tag—Provides a method for distinguishing between internal routes (learned by RIP) and external routes (learned from other protocols EGP or IGP e.g.:OSPF).

• IP address—Specifies the IP address for the entry.

• Subnet mask—Contains the subnet mask for the entry. If this field is zero, no subnet mask has been specified for the entry.

• Next hop—Indicates the IP address of the next hop to which packets for the entry should be forwarded.

• Metric—Indicates how many internet work hops (routers) have been traversed in the trip to the destination. This value is between 1 and 15 for a valid route, or 16 for an unreachable route.

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Example of RIPV1 Message

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Example RIP V1- Compatibility Message

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RIP Route-update

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N2N2N2N2

N3N3N3N3

N4N4N4N4

N5N5N5N5

N6N6N6N6

N1N1N1N1

AAAA

BBBB

CCCC

N1 1 -N2 1 -N3 1 -

①①①①

N2 1 -N4 1 -N5 1 -

①①①①

N3 1 -N6 1 -

①①①①

N2 1 -N4 1 -N5 1 -

②②②② RIP

N1 1 -N2 1 -N3 1 -N4 2 BN5 2 B

③③③③

Hop count Next hop

Updating routing table by RIP

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RIP Parameters

RIP Timers:

Periodic Update: 30 sec.Interval between route update advertisements

Route-Age out : 180 sec.Interval a route should stay 'live' in the routing table. This counter is reset every time the router hears an update for this route.

Junk Collection : 120 sec.How long to wait to delete a route after it has timed out.

Triggered Updates:

Triggered updates will be sent to peer router, when there is a change in the network. E.g. When a new router is added to the network. Or whena router is removed from the network.

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RIP Preventing Loop

Split Horizon:The router cannot advertise information about routes on an interface from which the information originates. Split horizon is enabled by default on the router.

E.g.: Router R1 learns a route for network N from R2 and then advertises to another router, R3. Split horizon prevents R2 from also advertising the route back to R1. However, after R1 stops advertising, R2 still advertises the route to R3 in 120 seconds.

Poison reverse:A router sets the metric of routes received from a neighbor to 16 and sends back these routes to the neighbor to help delete useless information from the neighbor’s routing table.

R1 advertises the loss to R2. When the update arrives, R2 removes the route, and advertises the loss to R3 in the next update. Thus, the maximum lag between R1 losing the route and R3 being notified is 30 seconds instead of 120.

Route Aggregation:

Route aggregation is a method of generating a more general summary route.Nothing butSupernetting.

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Count to Infinity Problem

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Disadvantages

Ø Maximum Hop Count 15

Ø Slow convergence

Ø With default configuration, each router broadcasts out all the routing

information it has to neighboring routers once every 30 seconds

There is lots of routing information traffic.

Ø Comparison is done with number of hops, so it’s difficult to choose

appropriate route based on connection band width

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Configuration:

ISAM-1 ISAM-2

In the above set up shows that two ports of different devices connected

and the interfaces on each device is to be enabled with RIP.

CLI RIP Configuration commands................

STEP-1: Create a VRF on SHUB

configure ip shub vrf 1 name routervrf fast-path-mode:ena-user-user-com

STEP-2: Create a vlan on SHUB in residential mode.

configure vlan shub id 777 mode residential-bridge name ROUTERVLAN

10.10.1.0/24

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Configuration

STEP-3: Make this VLAN as a layer-3 interface.

configure interface shub vlan-id 777

configure interface shub ip 777

configure interface shub ip 777 vrf-id 1

configure interface shub ip 777 ip-addr 10.10.10.1/24

configure interface shub vlan-id 777 admin-status up

STEP-4: Select a port that is to be enabled with RIP.Admin status & Operational status should be up.

configure interface shub port 3 port-type network

configure interface shub port 3 admin-status up

STEP-5: Eggress network port 3 to RB vlan created and make it as un-tag port.

configure vlan shub id 777 egress-port network:3

configure vlan shub id 777 untag-port network:3

configure bridge shub port 3 pvid 777

STEP-6: Enable RIP on the interface 10.10.10.1 .

configure rip interface 10.10.10.1 send rip2 receive rip2

default-metric 1 authentication none split-horizon enable

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Configuration

Redistribution:

To import routes from global routing table to RIP routing table.

Configure rip redistribution enable local static ospf

RIP Route-Map:

To tell whether routes can be transmit or deny to other router.

Configure rip route-map 777 sub-index 1 ip-addr 20.1.1.1/8 direction transmit

deny

Route Aggregation:

Routes on this address range will be aggregated and transmitted

Configure rip aggregation 160.1.0.0/16

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Show commands

Show rip routing-table ->To view all routes

Show rip statistics ->To view the interface details,bad-packets,bad-routes

info

Show rip global ->To view total number of RIP routes

Show rip peer ->To view the peer version,I.e neighbor

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OSPF And OSPF Router Types

OSPF is a link state routing protocol that updates the routing table only when network changes occur, rather than at a predefined interval. OSPF supports variable length subnet masks (VLSM) and route summarization.Algorithm used is Dijktra Algorithm

o Backbone Router: Interface connected to the backbone (Area 0).

o Area Border Router (ABR):Interfaces in multiple areas with at least one interface in area 0. Connects other areas to the backbone and maintains routing information for each connected area.

o Autonomous System Boundary Router (ASBR):

Ø Router located between OSPF autonomous system and a non-OSPF network.

Ø Redistribute routing information between networks.A router becomes an ASBR when OSPF is redistributing from other routing protocols, including static routes.

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OSPF Topology :

ASBR

ABR-1 ABR-2

InternalArea 51

Area 1

Area 0

172.16.0.0/16

172.16.1.0/24

172.16.51.0/24172.16.10.4/30

172.16.20.0/24

10.1.0.0/24

11.0.0.0/812.0.0.0/813.0.0.0/8

.1

.1

.2 .3

.5

.6

.1

Lo - RouterID192.168.2.1/32

Lo - RouterID192.168.1.1/32

Lo - RouterID192.168.3.1/32

Pri 100Pri 200

Lo - RouterID192.168.4.1/32

LSA-1

LSA-5

LSA-2

LSA-3

External Routes

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OSPF Area Types

Normal Areas:.

ü Standard areas are defined as areas that can accept intra-area, inter-area and external routes.

ü The backbone area is the central area to which all other areas in OSPF connect.

Stub Areas:

ü Stub areas do not accept routes belonging to external autonomous systems (AS).

ü Accepts inter-area and intra-area routes.

ü To reach the outside networks, the routers in the stub area use a default route which is injected into the area by the Area Border Router (ABR).

ü A stub area is typically configured in situations where the branch office need not know about all the routes to every other office, instead it could use a default route to the central office and get to other places from there.

Totally Stub Areas:

ü Do not allow routes other than intra-area and the default routes to be propagated within the area.

ü The ABR injects a default route into the area and all the routers belonging to this area use the default route to send any traffic outside the area.

ü On the ABR configure no-summary.

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OSPF Area Types

NSSA:ü Flexibility of importing a few external routes into the area while still trying to retain the stub

characteristic.

ü If the area is configured as a NSSA, then the ASBR generates a NSSA external link-state advertisement (LSA) (Type-7) which can be flooded throughout the NSSA area. These Type-7 LSAs are converted into Type-5 LSAs at the NSSA ABR and flooded throughout the OSPF domain

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NSSA Behaviour

RIP Routes from ASBR , enter into NSSA area as Type-7 LSA, from ABR it transmits

as Type-5 LSAs to other OSPF domains.

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LSA types

Type 1: Router link advertisements generated by each router for each area it belongs to. Flooded to a single area only (intra-area route).

Type 2: Network link advertisements generated by designated routers describing the set of routers attached to a particular network. Flooded to the area that contains the network (intra-area route). When a route crosses an OSPF Area Border Router (ABR), the route is known as an OSPF Inter-Area route.

Type 3/4: Summary link advertisements generated by ABRs describing inter-area routes. Type 3 describes routes to networks and is used for summarization. Type 4 describes routes to the ASBR (inter-area summary route).

Type 5: Generated by the ASBR and describes links external to the Autonomous System (AS). These are the redistributed (from other routing protocols including static routes) routes. Flooded to all areas except stub areas (external route).

Type 6: Group membership link entry generated by multicast OSPF routers.

Type 7: NSSA external routes generated by ASBR. Only flooded to the NSSA. External routes injected internally by ASBRs Areas other than Area 0 are LSAs of type 7. The ABR between will translate LSAs type 7 to LSAs type 5 from each Area to Area 0 (external route).

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OSPF interface types

Broadcast

ü Broadcast networks are multi-access in that they are capable of connecting more than two devices

ü Hello packets are multicast with the destination address 224.0.0.5

Point-point

ü Point-to-point networks, there is no need to configure the neighbor's address since there can be only one neighbor.

Non-Broadcast multi Access Network(NBMA)

ü Capable of connecting more than two routers but have no broadcast capability. A packet sent by one of the attached routers would not be received by all other attached routers.

ü Extra configuration may be necessary for routers on these networks to acquire their neighbors.

ü OSPF packets on NBMA OSPF routers all are unicast.

o Point-to-multipoint networks:

ü Special configuration of NBMA networks in which the networks are treated as a collection of point-to-point links.

ü Routers on these networks do not elect a DR and BDR, and because the networks are seen as point-to-point links,

ü OSPF packets are multicast.

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OSPF Data format

o Hello

ü OSPF packet type 1.

ü These packets are sent periodically on all interfaces (including virtual links) in order to establish and maintain neighbor relationships.

ü Packets are multicast on those physical networks having a multicast or broadcast capability, enabling dynamic discovery of neighboring routers.

ü Network mask, Hello Interval and RouterDeadIntervalvalues of must be common in a network. These parameters are included in Hello packets

o Database Description

ü OSPF packet type 2.

ü These packets are exchanged when an adjacency is being initialized

ü Multiple packets may be used to describe the databaseü The DD sequence number then increments until the complete database description has been sent.

o Link State Request

ü OSPF packet type 3.

ü The Link State Request packet is used to request the pieces of the neighbor's database that are more up to date.

ü Multiple Link State Request packets may need to be used.

ü Link State Request packets is the last step in bringing up an adjacency.

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OSPF Data format

o Link State Update

ü OSPF packet type 4.

ü These packets implement the flooding of link state advertisements.

ü Each Link State Update packet carries a collection of LSAs one hop further from its origin.

ü Several LSAs may be included in a single packet.

o Link State Acknowledgment

ü OSPF packet type 5.

ü To make the flooding of link state advertisements reliable, flooded advertisements are explicitly acknowledged.

ü This acknowledgment is accomplished through the sending and receiving of Link State Acknowledgment packets.

ü Multiple link state advertisements can be acknowledged in a single Link State Acknowledgment packet.

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OSPF Adjacency Process

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Timers

Hello Interval. between transmissions of Hello packets on the interface. This period is advertised in Hello packets that are transmitted from the interface.

Router Dead Interval. the router will wait to hear a Hello from a neighbor on the network to which the interface is connected before declaring the neighbor down.

Retransmit Interval. The period, in seconds, the router will wait between retransmissions of OSPF packets that have not been acknowledged.

Poll-interval-Time Interval waits before sending a Hello to a presumably dead neighbor

Transit delay:Transit delay is the estimated number of seconds to transmit a link-state update packet over the interface.

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Configuration

ISAM-1

Create Fast-path VRF

configure ip shub vrf 5 name routervrf5 fast-path-mode:ena-user-user-com

Create Shub VLAN

configure vlan shub id 202 name ISProutingVLAN mode residential-bridge

configure vlan shub id 202 egress-port network:4

Create L3 interface:

configure interface shub vlan-id 202

configure interface shub ip 202 vrf-id 5

configure interface shub ip 202 ip-addr 10.1.1.10/24

configure interface shub vlan-id 202 admin-status up

Configure OSPF

configure ospf as-border-router enable

configure ospf redistribution enable local static rip (To import routes from other protocols)

configure ospf area 0.0.0.0 interface 10.1.1.10 no disable

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Configuration

ISAM-2

Create Fast-path VRF

configure ip shub vrf 5 name routervrf5 fast-path-mode:dis-user-user-com

configure vlan shub id 202 name ISProutingVLAN mode residential-bridge

configure vlan shub id 202 egress-port network:4

Create L3 interface:

configure interface shub vlan-id 202

configure interface shub ip 202 vrf-id 5

configure interface shub ip 202 ip-addr 10.1.1.11/24

configure interface shub vlan-id 202 admin-status up

Configure OSPF

configure ospf as-border-router enable

configure ospf redistribution enable local static rip

configure ospf area 0.0.0.0 interface 10.1.1.11 no disable

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Configuration

Route Aggregation:

Configure ospf area 0.0.0.0 aggregate-addr 10.0.0.0/8