In Load Balancing Mode, a Backup Interface Frequently Alternates Between Up
and Down States
Fault Symptom
, interface backup is configured on RouterB, and the load balancing
mode is used for interface backup. When RouterA sends traffic to RouterD, a backup interface
frequently alternates between Up and Down states.
Figure 11-3
Networking diagram showing that a backup interface frequently alternates between
Up and Down
GE1/0/0
192.168.1.1/24
GE2/0/0
192.168.2.1/24
GE1/0/0
192.168.1.2/24
GE2/0/0
192.168.2.2/24
RouterB
RouterC
RouterA
RouterD
Fault Analysis
1.
Check the physical connection and configurations of the primary and backup interfaces on
RouterB. The two interfaces are correctly connected and configured. The two interfaces
work properly when interface backup is not configured.
2.
Check the interface backup configuration on RouterB. Run the
display this
command on
the primary interface of RouterB. If the following command output is displayed, the load
balancing threshold and maximum bandwidth are configured for the primary interface. This
indicates that the load balancing mode is used for interface backup.
#
interface GigabitEthernet1/0/0
ip address 192.168.1.1 255.255.255.0
standby interface GigabitEthernet 2/0/0 30
bandwidth 10000
standby threshold 80 20
#
3.
Run the
display ip routing-table
command on RouterB. Equal-cost routes have been
generated.
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 7 Routes : 7
Destination/Mask Proto Pre Cost Flags NextHop Interface
2.2.2.0/24 Static 60 0 RD 192.168.1.2
GigabitEthernet1/0/0
Static 60 0 RD 192.168.2.2
GigabitEthernet2/0/0
4.
As shown in the command output, only traffic from RouterA to RouterD is sent through
the primary interface on RouterB. When no traffic needs to be transmitted, the primary
interface GE1/0/0 is in Up state, and the backup interface GE2/0/0 is in Standby state. When
the volume of traffic to be transmitted exceeds the upper threshold, the backup interface
GE2/0/0 is used. Because there is only one data flow and the backup interface is selected
based on the hash algorithm, all packets are sent from the backup interface, and no traffic
is sent from the primary interface GE1/0/0. When the traffic volume of the primary interface
falls below the lower threshold, the backup interface is disabled. Consequently, the backup
interface frequently alternates between Up and Down states.
Huawei AR2200-S Series Enterprise Routers
Troubleshooting
11 Reliability
Issue 01 (2012-01-06)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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