Null route issue

Publication Date:  2014-11-24 Views:  434 Downloads:  0
Issue Description
Current S5700 is connected to NE40E, with a dedicated line connected to other site private network. One day, customer finds that the bandwidth usage between the interface of S5700 and NE40E increases to over 1 GB. Below is current configuration:

S5700:
Int vlan 2
Ip address 10.0.0.1 255.255.255.252 – vlan connected with NE40E

Int vlan 3
Ip address 10.1.1.1 255.255.255.252 – vlan connected with dediated line

Int gi 0/0/1
Port link-type access
Port type default vlan 2

Int gi 0/0/2
Port link-type access
Port type default vlan 3

Ip route-static 0.0.0.0 0.0.0.0 10.0.0.2 – connected with NE40E
Ip route-static 192.168.1.0 255.255.255.0 10.1.1.2 – connected with dedicated line

NE40E:
Int gi 8/0/1
Ip address 10.0.0.2 255.255.255.252

Ip route-static 192.168.1.0 255.255.255.0 10.0.0.1 – connected with S5700

Handling Process
Through troubleshooting the issue, we find that the dedicated line is disconnected with S5700 due to other technical maintenance. Tracroute result shows that if if 10.0.0.0/24 wants to access to 192.168.1.0/24, the traffic will then go to NE40E. But the next hop of 192.168.1.0/24 in NE40E is S5700, so there is loop causing high traffic between the equipment.
Solution
As the disconnection time is about 3hours and we can’t plug in the dedicated line cable back to S5700, Null0 route is temporarily created to solve the problem.

S5700:
Undo Ip route-static 192.168.1.0 255.255.255.0 10.1.1.2
Ip route-static 192.168.1.0 255.255.255.0 Null0

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