Chapter 8 SingleArea OSPF Routing Switching PresentationID 2008

Chapter 8: Single-Area OSPF Routing & Switching Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 1

Open Shortest Path First Single-area and Multiarea OSPF Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 2

Open Shortest Path First Single-area and Multiarea OSPF (cont. ) Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 3

OSPF Operation Process ID § Process ID ��� routing protocol OSPF �� ������ router ������������� OSPF process id ��������� enable OSPF ������ process OSPF process id ��������������� router ��� Command : R 1(config)#router ospf [Number] Example : R 1(config)#router ospf [100] Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 4

Configure Single-area OSPFv 2 The network Command: R 1(config)# router ospf process-id R 1(config-router)# network ip-address wildcard-mask area-id Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 5

OSPF Router ID OSPF Network Topology Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 6

OSPF Router IDs 1) highest IP address of a logical interface ( Loopback Interface ) 2) highest IP address of an active interface Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 7

OSPF Operation OSPF DR and BDR Designated Router (DR) : ����������� ������� Router ��������� Centralize ������� Packet LSA ���������� Router ������� Backup Designated Router (BDR) : ���� Router ������ DR ���� BDR ������� Packet �������� DR ����� BDR �������� DR ��� Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 8

OSPF Operation OSPF DR and BDR ���� Router ����� DR ��� BDR DR = Router Priority + Router ID ������ BDR = Router Priority + Router ID ����� 2 Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 9

OSPF Operation OSPF DR and BDR Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 10

Configure Single-area OSPFv 2 Configuring Passive Interfaces Use the passive-interface router configuration mode command to prevent the transmission of routing messages through a router interface, but still allow that network to be advertised to other routers. Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 11

OSPF Cost OSPF Metric = Cost = reference bandwidth / interface bandwidth (default reference bandwidth is 10^8) Cost = 100, 000 bps / interface bandwidth in bps Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 12

OSPF Cost OSPF Accumulates Cost of an OSPF route is the accumulated value from one router to the destination network. Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 13

OSPF Cost Default Interface Bandwidths On Cisco routers, the default bandwidth on most serial interfaces is set to 1. 544 Mb/s. Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 14

OSPF Cost Adjusting the Interface Bandwidths Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 15

OSPF Cost Manually Setting the OSPF Cost Both the bandwidth interface command the ip ospf cost interface command achieve the same result, which is to provide an accurate value for use by OSPF in determining the best route. Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 16

Verify OSPF Neighbors Verify that the router has formed an adjacency with its neighboring routers. Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 17

Verify OSPF Protocol Settings Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 18

Verify OSPF Process Information Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 19

Verify OSPF Interface Settings Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 20

Presentation_ID © 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 21