Example for Configuring Static Routes for Link Backup

Static Route Overview

Static routes use less bandwidth than dynamic routes and do not use CPU resources for route calculation and update analysis. They are manually configured by administrators. If a network fault occurs or the topology changes, static routes must be manually reconfigured as they cannot be automatically updated. Static routes have five parameters: destination IP address, mask, outbound interface, next hop, and priority.

Static routes are generally suitable for simple networks. However, they can be used on complex networks to improve network performance and ensure bandwidth for important applications.

Configuration Notes

Communication between two devices is bidirectional, so reachable routes must be available in both directions. To enable two devices to communicate through static routes, configure a static route on the local device and then configure a return route on the peer device.
If an enterprise network has two egresses, two equal-cost static routes can be configured for load balancing. In this case, two non-equal-cost static routes can be configured for active/standby backup. When the active link is faulty, traffic is switched from the active link to the standby link.
This example applies to all versions of all S series switches.

Networking Requirements

On the network shown in Figure 1, PC1 and PC2 are connected through four switches. Data traffic of PC1 can reach PC2 through two links: PC1->SwitchA->SwitchB->SwitchC->PC2 and PC1->SwitchA->SwitchD->SwitchC->PC2. To improve reliability, users want to implement backup between the two links. That is, traffic from PC1 to PC2 is first transmitted through the link that passes through SwitchB. When faults occur on this link, traffic is automatically switched to the link that passes through SwitchD.

In this scenario, ensure that all connected interfaces have STP disabled. If STP is enabled and VLANIF interfaces of switches are used to construct a Layer 3 ring network, an interface on the network will be blocked. As a result, Layer 3 services on the network cannot run normally.

Figure 1 Configuring static routes for link backup
click to enlarge

Configuration Roadmap

The configuration roadmap is as follows:

Create VLANs, add interfaces to the VLANs, and assign IP addresses to VLANIF interfaces.
Configure static routes in two directions of data traffic.
Configure IP address and default gateways for hosts.

Procedure

Specify the VLANs to which interfaces belong.

# Configure SwitchA. The configurations of SwitchB, SwitchC, and SwitchD are similar.

<HUAWEI> system-view
[HUAWEI] sysname SwitchA
[SwitchA] vlan batch 10 100 400
[SwitchA] interface gigabitethernet 0/0/1
[SwitchA-GigabitEthernet0/0/1] port link-type access
[SwitchA-GigabitEthernet0/0/1] port default vlan 10
[SwitchA-GigabitEthernet0/0/1] quit
[SwitchA] interface gigabitethernet 0/0/2
[SwitchA-GigabitEthernet0/0/2] port link-type trunk
[SwitchA-GigabitEthernet0/0/2] port trunk allow-pass vlan 100
[SwitchA-GigabitEthernet0/0/2] quit
[SwitchA] interface gigabitethernet 0/0/3
[SwitchA-GigabitEthernet0/0/3] port link-type trunk
[SwitchA-GigabitEthernet0/0/3] port trunk allow-pass vlan 400
[SwitchA-GigabitEthernet0/0/3] quit

Configure an IP address for each VLANIF interface.

# Configure SwitchA. The configurations of SwitchB, SwitchC, and SwitchD are similar.

[SwitchA] interface vlanif 10
[SwitchA-Vlanif10] ip address 10.1.1.1 24
[SwitchA-Vlanif10] quit
[SwitchA] interface vlanif 100
[SwitchA-Vlanif100] ip address 192.168.12.1 24
[SwitchA-Vlanif100] quit
[SwitchA] interface vlanif 400
[SwitchA-Vlanif400] ip address 192.168.14.1 24
[SwitchA-Vlanif400] quit

Configure static routes from PC1 to PC2.
# On SwitchA, configure two static routes with different priorities. The next hop of one route points to SwitchB, and that of the other route points to SwitchD. Subsequently, data traffic is first forwarded to SwitchB. When faults occur on the link that passes through SwitchB, the traffic is automatically switched to SwitchD.
```
[SwitchA] ip route-static 10.1.2.0 24 192.168.12.2
[SwitchA] ip route-static 10.1.2.0 24 192.168.14.2 preference 70
```
# Configure SwitchB.
```
[SwitchB] ip route-static 10.1.2.0 24 192.168.23.2
```
# Configure SwitchD.
```
[SwitchD] ip route-static 10.1.2.0 24 192.168.34.1
```
Configure static routes from PC2 to PC1 and ensure that the active and standby links in two directions are the same.
# On SwitchC, configure two static routes with different priorities. The next hop of one route points to SwitchB, and that of the other route points to SwitchD. Subsequently, data traffic is first forwarded to SwitchB. When faults occur on the link that passes through SwitchB, traffic is automatically switched to SwitchD.
```
[SwitchC] ip route-static 10.1.1.0 24 192.168.23.1
[SwitchC] ip route-static 10.1.1.0 24 192.168.34.2 preference 70
```
# Configure SwitchB.
```
[SwitchB] ip route-static 10.1.1.0 24 192.168.12.1
```
# Configure SwitchD.
```
[SwitchD] ip route-static 10.1.1.0 24 192.168.14.1
```
Configure hosts.
Assign IP address 10.1.1.2/24 and default gateway IP address 10.1.1.1 to PC1; assign IP address 10.1.2.2/24 and default gateway IP address 10.1.2.1 to PC2.

Verify the configuration.

# Check the IP routing table on SwitchA.

[SwitchA] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 9        Routes : 9        

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

       10.1.1.0/24  Direct  0    0           D   10.1.1.1        Vlanif10
       10.1.1.1/32  Direct  0    0           D   127.0.0.1       Vlanif10
       10.1.2.0/24  Static  60   0          RD   192.168.12.2    Vlanif100
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0
   192.168.12.0/24  Direct  0    0           D   192.168.12.1    Vlanif100
   192.168.12.1/32  Direct  0    0           D   127.0.0.1       Vlanif100
   192.168.14.0/24  Direct  0    0           D   192.168.14.1    Vlanif400
   192.168.14.1/32  Direct  0    0           D   127.0.0.1       Vlanif400

# Check detailed information about the IP routing table on SwitchA.

[SwitchA] display ip routing-table 10.1.2.0 24 verbose
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 2

Destination: 10.1.2.0/24
     Protocol: Static          Process ID: 0
   Preference: 60                    Cost: 0
      NextHop: 192.168.12.2     Neighbour: 0.0.0.0
        State: Active Adv Relied      Age: 00h13m13s
          Tag: 0                 Priority: medium
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x80000001       
 RelayNextHop: 0.0.0.0          Interface: Vlanif100
     TunnelID: 0x0                  Flags: RD

Destination: 10.1.2.0/24
     Protocol: Static          Process ID: 0
   Preference: 70                    Cost: 0
      NextHop: 192.168.14.2     Neighbour: 0.0.0.0
        State: Inactive Adv Relied    Age: 00h00m45s
          Tag: 0                 Priority: medium
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x80000002       
 RelayNextHop: 0.0.0.0          Interface: Vlanif400
     TunnelID: 0x0                  Flags: R

The IP routing table on SwitchA contains only one active route to network segment 10.1.2.0/24. Normally, data traffic from PC1 to PC2 is transmitted through the link that passes through SwitchB. Detailed information about the IP routing table on SwitchA shows two routes to network segment 10.1.2.0/24: one Active route that passes through SwitchB and the other Inactive route that passes through SwitchD. When faults occur on the active link, the Inactive route will become active to take over the traffic. This implements link backup.

Configuration Files

SwitchA configuration file

#
sysname SwitchA
#
vlan batch 10 100 400
#
interface Vlanif10
 ip address 10.1.1.1 255.255.255.0
#
interface Vlanif100
 ip address 192.168.12.1 255.255.255.0
#
interface Vlanif400
 ip address 192.168.14.1 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type access
 port default vlan 10
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 100
#
interface GigabitEthernet0/0/3
 port link-type trunk
 port trunk allow-pass vlan 400
#
ip route-static 10.1.2.0 255.255.255.0 192.168.12.2
ip route-static 10.1.2.0 255.255.255.0 192.168.14.2 preference 70
#
return

SwitchB configuration file

#
sysname SwitchB
#
vlan batch 100 200
#
interface Vlanif100
 ip address 192.168.12.2 255.255.255.0
#
interface Vlanif200
 ip address 192.168.23.1 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 100
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 200
#
ip route-static 10.1.1.0 255.255.255.0 192.168.12.1
ip route-static 10.1.2.0 255.255.255.0 192.168.23.2
#
return

SwitchC configuration file

#
sysname SwitchC
#
vlan batch 20 200 300
#
interface Vlanif20
 ip address 10.1.2.1 255.255.255.0
#
interface Vlanif200
 ip address 192.168.23.2 255.255.255.0
#
interface Vlanif300
 ip address 192.168.34.1 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type access
 port default vlan 20
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 200
#
interface GigabitEthernet0/0/3
 port link-type trunk
 port trunk allow-pass vlan 300
#
ip route-static 10.1.1.0 255.255.255.0 192.168.23.1
ip route-static 10.1.1.0 255.255.255.0 192.168.34.2 preference 70
#
return

SwitchD configuration file

#
sysname SwitchD
#
vlan batch 300 400
#
interface Vlanif300
 ip address 192.168.34.2 255.255.255.0
#
interface Vlanif400
 ip address 192.168.14.2 255.255.255.0
#
interface GigabitEthernet0/0/1
 port link-type trunk
 port trunk allow-pass vlan 400
#
interface GigabitEthernet0/0/2
 port link-type trunk
 port trunk allow-pass vlan 300
#
ip route-static 10.1.1.0 255.255.255.0 192.168.14.1
ip route-static 10.1.2.0 255.255.255.0 192.168.34.1
#
return

Relevant Information

Video

How to Configure a Static Route

How to Configure a Default Route

How to Configure a Floating Static Route