Tb2380 retana transitioning from eigrp to ospf_final

© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.

Transitioning Your Network From EIGRP To OSPFTB2380Alvaro Retana June 6, 2012


“When transitioning from one protocol to another there are lot of things to consider. In this session, attendees will hear a technical review of what to consider when transitioning from Enhanced Interior Gateway Routing Protocol (EIGRP) to Open Shortest Path First (OSPF). Attendees will gain a high-level overview of the protocols, network design considerations and more.”HP Discover 2012, Transitioning your network from EIGRP to OSPF

© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.4

Agenda

MotivationIntroductionEIGRP and OSPF overviewNetwork architecture considerationsTransition strategies

Implementation considerationsInformation hidingInter-area routing informationTraffic flow

OSPF for IPv6


By insisting on open standards in your network your business can realize multiple benefits

Motivation: Why Migrate to a Standard ProtocolLower capital expense• A vendor who knows you cannot easily incorporate a competitor’s products into your

network is much less motivated at the bargaining table

Best-in-class solutions• Committing yourself to a single vendor using proprietary protocol sharply reduces your

ability to seek out the best product on the market for each function of your network

Lower risk• By diversifying your suppliers, you are less vulnerable to a single software malfunction

affecting your entire network• Your network is also less at risk of product obsolescence, vendor buyouts, or business

failures

Innovation• The most competitive enterprises see their network as a fundamental tool for business

innovation• Agility, adaptation, and flexibility are the key qualities that keep your network ahead of

your competitors


Debunking The Myth Of a Single Vendor NetworkKey findings• No long term impact on OPEX• Lower TCO by at least 15-25% over five years• Multi vendor management tools ease the adoption of a second

vendor• Lasting decrease in network complexity

http://www.gartner.com/technology/media-products/reprints/hpprocurve/article7/article7.html




Introduction

All you need to know in 4 slides!


EIGRP and OSPF OverviewEnhanced Interior Gateway Protocol (EIGRP)

Open Shortest Path First (OSPF)

Standardization status

• Never submitted to any standards body • Standardized by the IETF• OSPFv2 = rfc2328

Routing algorithm

• Diffusing Update Algorithm (DUAL)• Developed at SRI International• DUAL guarantees 100% loop free paths• Sub-second convergence can be achieved

in the presence of feasible successors (no tuning needed)

• Dijkstra Shortest Path First (SPF)• Developed by Dr. Edsger Dijkstra in 1956• SPF and strict inter-area propagation rules

guarantee 100% loop free paths• Sub-second convergence can be obtained

through tuning or the use of IP Fast Reroute

Summarization and hierarchy

• Auto-summarization at major network boundaries

• Manual summarization at any point in the network

• Supports multiple levels of hierarchy• No topology information carried

• Manual Route Summarization and Automatic Topology Aggregation at area borders

• Supports two levels of hierarchy• Carries intra-area topology information

Metrics and load sharing

• Composite metric that can consider bandwidth, delay, load, reliability and MTU

• Can load share over both equal and unequal cost paths

• Path cost is derived from the link bandwidth• Can load share over equal cost paths

IPv6 support • Supported in a separate instance • OSPFv3 (rfc5340) was developed for IPv6 support

• Extensions exist to carry IPv4 in a separate instance


Network Architecture Considerations

Hierarchy structure & addressing schemeEIGRP allows for unlimited hierarchy levels, defined by the location of summarization points (manual or automatic)

− Route summarization is allowed at any router

OSPF allows for two levels of strict hierarchy, defined by the placement of areas

− Route summarization is allowed only at Area Border Routers (ABR)

− The topology is automatically aggregated

In general, the placement and type of an OSPF area should directly match the location and policies at the EIGRP

summarization points

EIGRP summarization points


Transition Strategies

Flash transition / overlay1. Configure OSPF on the network with a high administrative distance2. Verify the OSPF routing information

• The routes may not match if the EIGRP design used multiple summarization points

3. Lower the OSPF administrative distance• The routing table should now contain only OSPF routes

4. Remove EIGRP from the network

EIGRP EIGRPEIGRPOSPF OSPFOSPF


Transition Strategies (2)

Coexistence (redistribution)1. Configure mutual redistribution at the border between OSPF and EIGRP

network regions• Coexistence may be temporary while different regions are transitioned

OSPF

EIGRP EIGRP EIGRP

OSPF OSPFRedistribution Redistribution


Implementation Considerations

That was easy!! Are there other details to consider?


Information Hiding

Route summarization and topology aggregation are two common mechanisms that result in the reduction of information propagated throughout the network• EIGRP doesn’t carry topology information • The topology knowledge at any router is limited to its directly connected

neighbors• Route summarization can be configured at any point in the network• OSPF Area Border Routers (ABR) aggregate the topology and (can)

summarize the routing information• Every router knows the full topology of the local area• Route summarization can only occur at an ABR or ASBR


OSPF as a Distance Vector Protocol

Routing information is propagated between areas only when it is being usedOnly intra-area OSPF information in the routing table is converted to inter-area summary LSAs and sent to the backbone (Area 0)

Effect1. Before the transition, only Intra-area information will be present in the OSPF

database2. During the transition, redistribution may be needed – especially when

converting one area at a time


Intra-area Routing Considerations

EIGRP doesn’t have the concept of areas, which result in no limitations on the traffic flow patterns across the network

OSPF always prefers intra-area routes, so the placement of area boundaries may affect the existing traffic flow

100G

100G

100G100G

1G


EIGRP Traffic Flow

Metric = BW + delay

100G

100G

100G100G

1G


OSPF Traffic Flow

100G Link in Area 1

100G

100G

100G100G

1G

Area 1

Area 0


OSPF Traffic Flow (2)

100G Link in Area 0

100G

100G

100G100G

1G

Area 1

Area 0


OSPF Area Placement

Potential solutions1. Use a virtual link: place the 100G link in both areas2. Add more parallel 100G links, so that at least one is in each area3. Implement OSPF in a single-area configuration


OSPF for IPv6

OSPFv2 = IPv4OSPFv3 = IPv6


OSPF Evolution

Origin

al OSPF

spec

ifica

tion p

ublished

1989

OSPFv2

was

firs

t

published

1991

OSPF fo

r IPv

6 (aka

OSPF

v3)

was fi

rst p

ublished

1999

RFC 5

340

(OSP

F fo

r IPv

6)

2008

RFC 5

838 (Addre

ss

Fam

ilies i

n OSPF

v3)

2010

RFC 2

328 (OSPF

v2)

1998


OSPFv3 and v2 Similarities

• The same 5 packet types but some fields have been changed

• Mechanisms for neighbor discovery and adjacency formation

• Interface types• P2P, P2MP, Broadcast, NBMA, Virtual

• LSA flooding and aging• DR, BDR election, area support, SPF• Nearly identical LSA types

Packet type12345

Link state updateLink state acknowledgment

DescriptionHelloDatabase descriptionLink state request


OSPFv3 and OSPFv2 Differences

• Changes made to OSPFv2 to accommodate increased address size of IPv6• OSPF now runs on per-link, not per-subnet• Removal of addressing semantics from OSPF packets and LSAs making it network

protocol independent• New LSAs created to carry IPv6 addresses and prefixes • Addition of flooding scope (similar to RFC2370)• Explicit support for multiple instances per link• Use of IPv6 link-local addresses for protocol processing and providing next hop

information during packet forwarding• Authentication method changes• Packet format & LSA’s header format changes • Handling of unknown LSA types


OSPFv2 had two flooding scopes• AS wide• Area wide

OSPFv3 has three flooding scopes:• AS scope - LSA is flooded throughout the AS• Area scope - LSA is flooded only within an area• Link-local scope - LSA is flooded only on the local link

OSPFv3 Flooding Scope

LS age U S2 S1 LSA Function Code

LS age Options LS type


OSPFv3 Flooding ScopeU (unrecognized) bit is used to indicate to a router how to handle an LSA if it is unrecognized

S2 / S1 bit indicates the three flooding scopes

S2 S10 00 11 01 1

Flooding scopeLink-local flooding scopeArea flooding scopeAS flooding scopeReserved

U-bit01

Treat this LSA as if it has link-local ScopeStore and flood this LSA as if type understood

LSA handling


OSPFv3 LSA Types

List of LSAs in OSPFv3

LSA name LS type code Flooding scope LSA function codeRouter LSA 0x2001 Area scope 1Network LSA 0x2002 Area scope 2Inter-Area-Prefix-LSA 0x2003 Area scope 3Inter-Area-Router-LSA 0x2004 Area scope 4AS-External-LSA 0x4005 AS scope 5Group-membership-LSA 0x2006 Area scope 6Type-7-LSA 0x2007 Area scope 7Link-LSA 0x0008 Link-local scope 8Intra-Area-Prefix-LSA 0x2009 Area scope 9


Dual-stack OSPF Deployment

Multi-instanceMultiple instances of OSPF on a given linkEnhances the ability to isolate the resources associated with both router and networkInstance specific prioritization for PDUs and routing calculations

Convergence considerationsIGPs will compete over processor cycles based on their relative tuning• If you configure the IPv4 and IPv6 IGPs the same way (aggressively tuned for fast

convergence), naturally expect a doubling of their stand-alone operation convergence time

• If the IPv6 IGP is operating under default settings, the convergence time for the optimally tuned IPv4 IGP is not significantly affected


Conclusions / Summary

By insisting on open standards in your network your business can realize multiple benefits

It is important to understand the differences in routing protocol operation and the implications on the current network before starting a transition• Location of summarization points• Network hierarchy• Metrics, load sharing and traffic flow• Information propagation: topology and reachability information• Transition mechanisms (and which one is best for your network)• Protocol evolution

Always the best protocol is the one which is right for your network


Tools to Help Our Clients • Read about the FlexNetwork Architecture

• Learn about Virtual Application Networks

• Discover Intelligent Management Center

• View the HPN Portfolio Matrix Guide

• Learn about networking services from HP Technical Services

• Learn about networking career certifications from HP ExpertONE

http://h20195.www2.hp.com/v2/GetPDF.aspx/4AA3-6037ENW.pdf


http://h17007.www1.hp.com/docs/interop/HP_Networking_Intelligent_Management_Center_Standard_Software_Platform_Datasheet_4AA3-0694ENW.pdf


http://www8.hp.com/us/en/services/services-detail.html?compURI=tcm:245-846146

http://www.hp.com/certification/expert_one-networking.html


After the eventVisit these demos

Find out more

Attend these sessions

• TB2375, Simplify large scale secure WAN deployments, Wednesday @ 4pm

• TB3244, IPv6 Deployment: Understanding internal IPV6 protocols, Tuesday @ 4pm

• HP Flex Network Architecture

• A holistic approach to IPV6

• Dynamic Virtual Private Network (DVPN)

• Contact your sales rep

• Visit the HP Networking website at: http://www.hp.com/networking

Your feedback is important to us. Please take a few minutes to complete the session survey.

http://www.hp.com/networking

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Q&A


Thank you

Tb2380 retana transitioning from eigrp to ospf_final

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Transcript of Tb2380 retana transitioning from eigrp to ospf_final