Configuring The OSPF Router-ID

Real World Application & Core Knowledge

In lab 9-1, the process of the Router-ID determination was discussed and through out Section 9 labs when you’ve used the show ip ospf neighbor command and I’m sure you’ve noticed the neighbor id and that it was the IP Address of the neighbors loopback0 interface. As discussed in Lab 9-1, there is a reason for this. The Router-ID uniquely identifies a router in an autonomous system, no two routers in an OSPF autonomous system can have the same router-id.

If a router-id is not configured manually in the OSPF routing process the router will automatically configure a router-id determined from the highest IP address of a logical interface (loopback interface) or the highest IP address of an active interface. When referring to a higher IP address, step back and look at the IP address as a whole number. For example, 1.1.1.1 translates to 1,111 and 2.2.2.2 translates to 2,222; in which case 2,222 is a higher number than 1,111.

The router id is used in several OSPF related commands such as the specifying a specific neighbor when clearing a neighbor relationship or when viewing neighbor parameters by using the show ip ospf neighbor rid.

When configuring a router-id, the neighbors will not be updated automatically until that router has failed or the OSPF process has been cleared and the neighbor relationship has been re-established.

In this lab you will statically configure the Router-ID’s on all routers in the topology using the router number as the router-id. i.e; R1′s router-id would be 1.1.1.1

Familiarize yourself with the following new command(s);

router-id x.x.x.x – This command is executed in OSPF router configuration mode to statically configure a router id on a specific neighbor.

show ip ospf proc-id – This command is executed in privileged mode to view OSPF process parameters such s the local router-id and OSPF area information related to that router.

The following logical topology shown below is used in labs found through out Section 9 – Configuring OSPF;

Lab Prerequisites

• If you completed lab 9-5 you can start where you’ve left off or you can load the Free CCNA Workbook GNS3 topology; start and establish a console session with R1, R2, R3, R4, R5 and SW1 then load their initial configurations included below by copying the config from the textbox and pasting it into the routers console.

Initial Configurations

!################################################## !#  Free CCNA Workbook Lab 9-6 R1 Initial Config  # !################################################## ! enable configure terminal ! hostname R1 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.10.1 255.255.255.0 ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.1 255.255.255.248  encapsulation frame-relay  serial restart-delay 0  frame-relay map ip 10.1.245.5 125 broadcast  frame-relay map ip 10.1.245.4 124 broadcast  frame-relay map ip 10.1.245.2 122 broadcast  no frame-relay inverse-arp  no shut  exit ! router ospf 1  log-adjacency-changes  network 10.1.245.1 0.0.0.0 area 0  network 10.55.10.1 0.0.0.0 area 1  neighbor 10.1.245.2  neighbor 10.1.245.4  neighbor 10.1.245.5 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-6 R2 Initial Config  # !################################################## ! enable configure terminal ! hostname R2 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.20.1 255.255.255.0 ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.2 255.255.255.248  encapsulation frame-relay  ip ospf priority 0  serial restart-delay 0  no frame-relay inverse-arp  frame map ip 10.1.245.1 221 broadcast  frame map ip 10.1.245.4 221  frame map ip 10.1.245.5 221  no shut ! interface Serial1/2  ### POINT-TO-POINT LINK TO R3 ###  ip address 10.1.23.1 255.255.255.252  encapsulation ppp  serial restart-delay 0  no shut  exit ! router ospf 1  log-adjacency-changes  network 10.1.23.1 0.0.0.0 area 3  network 10.1.245.2 0.0.0.0 area 0  network 10.55.20.1 0.0.0.0 area 2 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-6 R3 Initial Config  # !################################################## ! enable configure terminal ! hostname R3 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.30.1 255.255.255.0 ! interface Serial1/1  description ### POINT-TO-POINT LINK TO R2 ###  ip address 10.1.23.2 255.255.255.252  encapsulation ppp  no shut  exit ! router ospf 1  log-adjacency-changes  network 10.1.23.2 0.0.0.0 area 3  network 10.55.30.1 0.0.0.0 area 3 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-6 R4 Initial Config  # !################################################## ! enable configure terminal ! hostname R4 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.40.1 255.255.255.0 ! interface FastEthernet0/0  description ### REAL NETWORK ###  ip address 10.45.1.1 255.255.255.0  no shut ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.4 255.255.255.248  encapsulation frame-relay  ip ospf priority 0  serial restart-delay 0  no frame-relay inverse-arp  frame map ip 10.1.245.1 421 broadcast  frame map ip 10.1.245.2 421  frame map ip 10.1.245.5 421  no shut ! interface Serial1/1  description ### POINT-TO-POINT LINK TO R5 ###  ip address 10.1.45.1 255.255.255.252  encapsulation ppp  serial restart-delay 0  no shut  exit ! router ospf 1  log-adjacency-changes  network 10.1.45.1 0.0.0.0 area 45  network 10.1.245.4 0.0.0.0 area 0  network 10.45.1.1 0.0.0.0 area 45  network 10.55.40.1 0.0.0.0 area 4 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-6 R5 Initial Config  # !################################################## ! enable configure terminal ! hostname R5 no ip domain-lookup ! interface Loopback0  description ### SIMULATED NETWORK ###  ip address 10.55.50.1 255.255.255.0 ! interface FastEthernet0/0  description ### REAL NETWORK ###  ip address 10.45.1.2 255.255.255.0  no shut ! interface Serial1/0  description ### PHYSICAL FRAME RELAY INTERFACE ###  ip address 10.1.245.5 255.255.255.248  encapsulation frame-relay  ip ospf priority 0  serial restart-delay 0  no frame-relay inverse-arp  frame map ip 10.1.245.1 521 broadcast  frame map ip 10.1.245.2 521  frame map ip 10.1.245.4 521  no shut ! interface Serial1/1  description ### POINT-TO-POINT LINK TO R4 ###  ip address 10.1.45.2 255.255.255.252  encapsulation ppp  serial restart-delay 0  no shut  exit ! router ospf 1  log-adjacency-changes  network 10.1.45.2 0.0.0.0 area 45  network 10.1.245.5 0.0.0.0 area 0  network 10.45.1.2 0.0.0.0 area 45  network 10.55.50.1 0.0.0.0 area 5 ! line con 0  logging sync  no exec-timeout ! end

!################################################## !#  Free CCNA Workbook Lab 9-5 SW1 Initial Config # !################################################## ! enable configure terminal ! hostname SW1 no ip domain-lookup ! line con 0  logging sync  no exec-timeout ! end

Lab Objectives

• Configure each router with a router-id that reflects the router number. i.e; R1′s Router-id would be 1.1.1.1
• Clear the OSPF process on each router and verify on R1 that the new router ID’s are be used by viewing R1′s OSPF neighbors.

Lab Instruction

Objective 1. – Configure each router with a router-id that reflects the router number. i.e; R1′s Router-id would be 1.1.1.1

R1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R1(config)#router ospf 1 R1(config-router)#router-id 1.1.1.1 Reload or use "clear ip ospf process" command, for this to take effect R1(config-router)#end R1#

R2#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R2(config)#router ospf 1 R2(config-router)#router-id 2.2.2.2 Reload or use "clear ip ospf process" command, for this to take effect R2(config-router)#end R2#

R3#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R3(config)#router ospf 1 R3(config-router)#router-id 3.3.3.3 Reload or use "clear ip ospf process" command, for this to take effect R3(config-router)#end R3#

R4#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R4(config)#router ospf 1 R4(config-router)#router-id 4.4.4.4 Reload or use "clear ip ospf process" command, for this to take effect R4(config-router)#end R4#

R5#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R5(config)#router ospf 1 R5(config-router)#router-id 5.5.5.5 Reload or use "clear ip ospf process" command, for this to take effect R5(config-router)#end R5#

Objective 2. – Clear the OSPF process on each router and verify on R1 that the new router ID’s are be used by viewing R1′s OSPF neighbors.

R1#clear ip ospf 1 proc Reset OSPF process? [no]: y R1#

R2#clear ip ospf 1 proc Reset OSPF process? [no]: y R2#

R3#clear ip ospf 1 proc Reset OSPF process? [no]: y R3#

R4#clear ip ospf 1 proc Reset OSPF process? [no]: y R4#

R5#clear ip ospf 1 proc Reset OSPF process? [no]: y R5#

Once you’ve cleared the OSPF process as shown above on R1 through R5 the neighbor relationships will drop and reform, once all neighbor relationships have been re-established you can then view the ospf neighbor table on R1 to verify that the router-id’s have indeed been changed;

R1#show ip ospf database Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 0 FULL/DROTHER 00:01:39 10.1.245.2 Serial1/0 4.4.4.4 0 FULL/DROTHER 00:01:35 10.1.245.4 Serial1/0 5.5.5.5 0 FULL/DROTHER 00:01:59 10.1.245.5 Serial1/0 R1#

To verify that R3′s router ID has been changed you can view the neighbor relationships on R2 as shown below;

R2#show ip ospf database

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/DR         00:01:50    10.1.245.1      Serial1/0
3.3.3.3           0   FULL/  -        00:00:36    10.1.23.2       Serial1/2
R2#