2 local routers 1 ISP failover

[Cisco eng]

Hi,

I've been given the task to configure 2 Cisco 1921 routers in LAN/WAN failover mode, and if it is possible even do load-balancing.

I used HSRP for this and when I turn off the primary router, the secondary router takes over nicely. When the primary router comes back up, it takes over again. But when both routers are online (primary router active/ secondary router standby) the WAN link becomes unstable with alot of ping-timeouts. When I administratively shut down the WAN port of the secondary router, the WAN link becomes stable again.

Below the configuration I use, what can be done to prevent the unstable connection? Or is there a better way to configure this?

Primary router:

interface GigabitEthernet0/0
 description Connection-To-Internet
 ip address *.*.*.28 255.255.255.128
 ip access-group FIREWALL in
 ip nat outside
 ip virtual-reassembly in
 standby 1 ip *.*.*.30
 standby 1 priority 200
 standby 1 preempt
 duplex full
 speed 100

!

interface Vlan1
 description Connection-To-LAN
 ip address 192.168.0.248 255.255.255.0
 ip pim sparse-mode
 ip nat inside
 ip virtual-reassembly in
 ip tcp adjust-mss 1452
 standby 2 ip 192.168.0.247
 standby 2 priority 200
 standby 2 preempt
 standby 2 track 1 decrement 10

!

ip route 0.0.0.0 0.0.0.0.0 *.*.*.1

Secondary router:

interface GigabitEthernet0/0
 description Connection-To-Internet
 ip address *.*.*.29 255.255.255.128
 ip access-group FIREWALL in
 ip nat outside
 ip virtual-reassembly in
 standby 1 ip *.*.*.30
 standby 1 preempt
 duplex full
 speed 100

!

interface Vlan1
 description Connection-To-LAN
 ip address 192.168.0.249 255.255.255.0
 ip pim sparse-mode
 ip nat inside
 ip virtual-reassembly in
 ip tcp adjust-mss 1452
 standby 2 ip 192.168.0.247
 standby 2 preempt
 standby 2 track 1 decrement 10

!

ip route 0.0.0.0 0.0.0.0.0 *.*.*.1

Thanks,

Tom

[Mohit Sahai · Accepted solution]

Hello Tom,

Fir this issue I think combination of IPSLA and EEM script would help you out.

Below steps can be followed,

Step1: Configure IPSLA to ping the WAN IP.

Step 2: If the packet drops are detected, the IPSLA state changes and that should trigger the WAN interface to get shut down.

Below discussion refers to the shutting the BGP if there is packet drops on the issue is observed.

Similarly we could configure the EEM to shut the link down when the packet drops are observed.

More preciously you can find the EEM to shut the link 

https://supportforums.cisco.com/discussion/10794236/shut-interface-if-no-ping-response-using-ip-sla-eem

Hope this helps you to achieve the requirement.

Let me know if further clarification is needed.

Thanks,

Mohit 

[Cisco eng]

Hi Mohit,

Thank you for this information, this could be what i'm looking for. There's no way for me to test this right now, my boss changed the planning to have this done early next year.

I will mark your answer as correct. If it does not work I will open this forum discussion again and will report my findings.

Thanks!

Tom