Developing an optimum Design for Layer 3

Kapitel 3 fra CCDP ARCH bogen.

This article is under development....

At designe avancerede IP adresserings løsninger

NAT

Content Load-Balancing Device

En enhed der fordeler belastningen mellem flere Servere. For eksempel en enhed der fordeler forespørgsler fra WEB-brugere mellem ti identiske WEB-servere. Det kan være baseret på forskellige faktorer

• Antallet af forbindelser til hver server
• CPU belastning på Serverne
• En kombination af flere faktorer der beskriver servernes belastning

For eksempel Cisco CSS 11500 Series Content Services Switch

Designing avanceret Routning

Inappropriate Transit Traffic

Dont do the job of your ISP

Defensive filtering

Trust no one

Route redistribution

Prefix-list, Route-maps or Tagging of routes

Migrating Between Routing Protocols

Two companies have been merged. Company A are running EIGRP and Company B are running OSPF.
Step 1: Redistribute between A & B
Step 2: Enable OSPF in comapny A, and make sure it has the highest Administrativ Distance
Step 3: When OSPF is running and is fully converged, Remove EIGRP

Designing Scalable OSPF Design

OSPF Scalability best practise

• Any one Router should have no more than 60 adjacent neighbors
• An area should have no more than 50 Routers
• Any one Router should not be in mothe than three areas
• Already heavily loaded Routers should not be DR and BDR

Designing Areas

Network topology and addressing should be designed initially with division of areas in mind.

General advice about OSPF design is:

• Minimize the routing information advertised into and out of the area.
• Experience shows that you should be conservative about adding routers to the backbone area.
• Make it simple
• Make nonbackbone areas stub or totally stubby areas
• Make it summarized

OSPF Areas & Area Summarization

Yada yada OMG OSPF

If hello timers are set to 1/3 second for 300 interfaces, each with 10 neighbors, the router would have to generate 900 hellos per second.
When the 3000 neighbors send 3 hellos per second back to the router, it has to process a total of 9900 hellos per second.

Det er jo ikke realistisk, Cisco tag dig sammen

Incremental SPF

iSPF calculate only the part of the path tree that has changed.
The iSPF feature has been available since Cisco IOS Software Release 12.0(24)S, 12.3(2)T, 12.2(18)S, and 12.2(27)SBC. It is enabled with the iSPF router command under an OSPF process.

SPF & iSPF comparison

Designing Scalable BGP Designs

Vis BGP slide...

Scaling iBGP with Route Reflectors

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Scaling BGP with Confederations

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