Example for Configuring DR Election of OSPF

CloudEngine 12800 and 12800E V200R005C10 Configuration Guide - IP Unicast Routing

This document describes the configurations of IP Unicast Routing, including IP Routing, Static Route, RIP, RIPng, OSPF, OSPFv3, IPv4 IS-IS, IPv6 IS-IS, BGP, Routing Policy, and PBR.

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Example for Configuring DR Election of OSPF

Networking Requirements

As shown in Figure 5-34, SwitchA has the highest priority of 100 on the network and is elected as the DR; SwitchC has the second highest priority of 2 and is elected as the BDR; SwitchB has a priority of 0 and therefore cannot be elected as the DR or BDR; SwitchD is not configured with a priority and therefore uses the default priority of 1.

Figure 5-34 Networking diagram for configuring DR election of an OSPF process

Configuration Roadmap

The configuration roadmap is as follows:

Configure the ID of the VLAN to which each interface belongs.
Configure a VLANIF interface for each VLAN and assign an IP address to each VLANIF interface.
Configure a router ID, enable OSPF, and specify network segments on each Switch.
Check the DR/BDR status of each Switch using its default DR priority.
Set the DR priority of the interface on each Switch and check the DR/BDR status on each Switch.

Procedure

Configure a VLAN for each interface.

<HUAWEI> system-view
[~HUAWEI] sysname SwitchA
[*HUAWEI] commit
[~SwitchA] vlan 10
[*SwitchA-vlan10] quit
[*SwitchA] interface 10ge 1/0/1
[*SwitchA-10GE1/0/1] port link-type trunk
[*SwitchA-10GE1/0/1] port trunk allow-pass vlan 10
[*SwitchA-10GE1/0/1] quit
[*SwitchA] commit

The configurations of Switch B, Switch C, and Switch D are similar to the configuration of Switch A, and are not provided here.

Configure a VLANIF interface for each VLAN and assign an IP address to each VLANIF interface.
```
[~SwitchA] interface vlanif 10
[*SwitchA-Vlanif10] ip address 192.168.1.1 24
[*SwitchA-Vlanif10] commit
[~SwitchA-Vlanif10] quit
```
The configurations of SwitchB, SwitchC, and SwitchD are similar to the configuration of SwitchA, and are not provided here.

Configure basic OSPF functions.

# Configure SwitchA.

[~SwitchA] router id 10.1.1.1
[*SwitchA] ospf
[*SwitchA-ospf-1] area 0
[*SwitchA-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255
[*SwitchA-ospf-1-area-0.0.0.0] quit
[*SwitchA-ospf-1] quit
[*SwitchA] commit

# Configure Switch B.

[~SwitchB] router id 10.2.2.2
[*SwitchB] ospf
[*SwitchB-ospf-1] area 0
[*SwitchB-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255 
[*SwitchB-ospf-1-area-0.0.0.0] quit
[*SwitchB-ospf-1] quit
[*SwitchB] commit

# Configure SwitchC.

[~SwitchC] router id 10.3.3.3
[*SwitchC] ospf
[*SwitchC-ospf-1] area 0
[*SwitchC-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255 
[*SwitchC-ospf-1-area-0.0.0.0] quit
[*SwitchC-ospf-1] quit
[*SwitchC] commit

# Configure SwitchD.

[~SwitchD] router id 10.4.4.4
[*SwitchD] ospf
[*SwitchD-ospf-1] area 0
[*SwitchD-ospf-1-area-0.0.0.0] network 192.168.1.0 0.0.0.255 
[*SwitchD-ospf-1-area-0.0.0.0] quit
[*SwitchD-ospf-1] quit
[*SwitchD] commit

# Display the neighbor information on SwitchA to check the DR and BDR status.

[~SwitchA] display ospf peer
 
OSPF Process 1 with Router ID 10.1.1.1
 Area 0.0.0.0 interface 192.168.1.1(Vlanif10)'s neighbors
   Router ID: 10.2.2.2      Address: 192.168.1.2      GR State: Normal
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 32  sec
   Neighbor is up for 00:00:00
   Authentication Sequence: [~ 0 ]
 
   Router ID: 10.3.3.3      Address: 192.168.1.3      GR State: Normal
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 37  sec
   Neighbor is up for 00:04:06
   Authentication Sequence: [~ 0 ]
 
   Router ID: 10.4.4.4      Address: 192.168.1.4      GR State: Normal
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 37  sec
   Neighbor is up for 00:03:53
   Authentication Sequence: [~ 0 ]

As shown in the neighbor information on SwitchA, the DR priority of SwitchA is the default value of 1 and its neighbor status indicates that SwitchD functions as the DR and SwitchC functions as the BDR.

When switches have the same DR priority, the switch with a higher router ID is elected as the DR. After DR/BDR election is complete, a new switch cannot become the DR even if it has the highest DR priority.

Set the DR priority on each VLANIF interface.

# Configure SwitchA.

[~SwitchA] interface Vlanif 10
[~SwitchA-Vlanif10] ospf dr-priority 100
[*SwitchA-Vlanif10] quit
[*SwitchA] commit

Configure Switch B.

[~SwitchB] interface Vlanif 10
[~SwitchB-Vlanif10] ospf dr-priority 0
[*SwitchB-Vlanif10] quit
[*SwitchB] commit

# Configure SwitchC.

[~SwitchC] interface Vlanif 10
[~SwitchC-Vlanif10] ospf dr-priority 2
[*SwitchC-Vlanif10] quit
[*SwitchC] commit

# Check the DR/BDR status.

[~SwitchD] display ospf peer
 
OSPF Process 1 with Router ID 10.4.4.4
 Area 0.0.0.0 interface 192.168.1.4(Vlanif10)'s neighbors
   Router ID: 10.1.1.1      Address: 192.168.1.1      GR State: Normal
   State: Full  Mode:Nbr is  Slave  Priority: 100
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 31  sec
   Neighbor is up for 00:11:17
   Authentication Sequence: [~ 0 ]

   Router ID: 10.2.2.2      Address: 192.168.1.2      GR State: Normal
   State: Full  Mode:Nbr is  Slave  Priority: 0
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 35  sec
   Neighbor is up for 00:11:19
   Authentication Sequence: [~ 0 ]

   Router ID: 10.3.3.3      Address: 192.168.1.3      GR State: Normal
   State: Full  Mode:Nbr is  Slave  Priority: 2
   DR: 192.168.1.4  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 33  sec
   Neighbor is up for 00:11:15
   Authentication Sequence: [~ 0 ]

The DR priorities configured on interfaces do not take effect immediately.

Restart the OSPF processes.
In the user view of each Switch, run the reset ospf 1 process command simultaneously to restart the OSPF processes.

Verify the configuration.

# Check the OSPF neighbor status.

[~SwitchD] display ospf peer
 
OSPF Process 1 with Router ID 10.4.4.4
 Area 0.0.0.0 interface 192.168.1.4(Vlanif10)'s neighbors
   Router ID: 10.1.1.1      Address: 192.168.1.1      GR State: Normal
   State: Full  Mode:Nbr is  Slave  Priority: 100
   DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 35  sec
   Neighbor is up for 00:07:19
   Authentication Sequence: [~ 0 ]
 
   Router ID: 10.2.2.2      Address: 192.168.1.2      GR State: Normal
   State: Full  Mode:Nbr is  Master  Priority: 0
   DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 35  sec
   Neighbor is up for 00:00:00
   Authentication Sequence: [~ 0 ]
 
   Router ID: 10.3.3.3      Address: 192.168.1.3      GR State: Normal
   State: Full  Mode:Nbr is  Slave  Priority: 2
   DR: 192.168.1.1  BDR: 192.168.1.3  MTU: 0
   Dead timer due in 37  sec
   Neighbor is up for 00:07:17
   Authentication Sequence: [~ 0 ]

# Check the OSPF interface status.

[~SwitchA] display ospf interface
 
OSPF Process 1 with Router ID 10.1.1.1
 
 Area: 0.0.0.0          (MPLS TE not enabled)

 Interface           IP Address      Type         State    Cost    Pri  
 Vlanif10            192.168.1.1     Broadcast    DR      1       1    
 [~SwitchB] display ospf interface
 
OSPF Process 1 with Router ID 10.2.2.2
 
 Area: 0.0.0.0          (MPLS TE not enabled)

 Interface           IP Address      Type         State    Cost    Pri  
 Vlanif10            192.168.1.2     Broadcast    DROther  1       0

If all neighbors are in Full state, the local device establishes adjacencies with all its neighbors. If a neighbor stays in 2-way state, neither the local device nor the neighbor is the DR or BDR, and therefore they do not need to exchange LSAs.

If the OSPF interface of a device is in DROther state, the device is neither the DR nor the BDR.

Configuration Files

Configuration file of SwitchA

#
 sysname SwitchA
#
 vlan batch 10
#
 router id 10.1.1.1
#
interface Vlanif10
 ip address 192.168.1.1 255.255.255.0
 ospf dr-priority 100
#
interface 10GE1/0/1
 port link-type trunk
 port trunk allow-pass vlan 10 
#
ospf 1
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

Configuration file of SwitchB

#
 sysname SwitchB
#
 vlan batch 10
#
 router id 10.2.2.2
#
interface Vlanif10
 ip address 192.168.1.2 255.255.255.0
 ospf dr-priority 0
#
interface 10GE1/0/1
 port link-type trunk
 port trunk allow-pass vlan 10 
#
ospf 1
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

Configuration file of SwitchC

#
 sysname SwitchC
#
 vlan batch 10
#
 router id 10.3.3.3
#
interface Vlanif10
 ip address 192.168.1.3 255.255.255.0
 ospf dr-priority 2
#
interface 10GE1/0/1
 port link-type trunk
 port trunk allow-pass vlan 10 
#
ospf 1
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

Configuration file of SwitchD

#
 sysname SwitchD
#
 vlan batch 10
#
 router id 10.4.4.4
#
interface Vlanif10
 ip address 192.168.1.4 255.255.255.0
#
interface 10GE1/0/1
 port link-type trunk
 port trunk allow-pass vlan 10
#
ospf 1
 area 0.0.0.0
  network 192.168.1.0 0.0.0.255
#
return

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Updated: 2021-09-17

Document ID: EDOC1100075354

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