How to achieve Link Failover by using Dual routers.

[Ruheal Maqsood]

Dear Experts,

I want to achieve link failover. There are two routers in my setup Router A and Router B. ISP-A ONT wired link is terminated on Router-A and ISP-B Microwave Link is terminated on Router-B.

I want to make ISP-B as a PRIMARY wan and ISP-A as BACKUP wan so that users inside the LAN can access webserver z.z.z.z   24/7. In this case how to configure/achieve link failover ?

Sample design is attached with the query

[Philip D'Ath]

You need provider indepenent addres space to do this, or for one ISP to give you a block of /24 address space and allow another ISP to route it (both cases unlikely).

That being the case, you can't achieve this alone.  You can use Smart DNS servers like Amazon Route53 which can test two different IP addresses and give out whichever one is working - or much easier - put the service into Amazon AWS.

[Philip D'Ath]

Assuming you can not get provider independent address space, this is much easier to do using Cisco Meraki kit.

Here is some info for you to read:
https://documentation.meraki.com/MX-Z/Firewall_and_Traffic_Shaping/MX_Load_Balancing_and_Flow_Preferences

If you have less than 50 users you could consider using the MX65. Here is a sizing guide:
https://meraki.cisco.com/products/appliances#models

[Ruheal Maqsood]

Currently I am restricted with current devices. Can't move with further demand.

[Georg Pauwen]

Hello,

sorry if I might have missed that, but are you actually using BGP with your ISPs ?

[Ruheal Maqsood]

No. Static default routing

[Georg Pauwen · Accepted solution]

Hello,

here is what I have in mind:

Set up HSRP between your LAN interfaces, then create an IP SLA on both routers tracking the WAN interface of the respective other routers. An EEM script on each router tracks the SLA and executes commands that enable and disable the WAN interface on the other router and installs the default route.

The easiest would be for you to post the configs of both routers, so the necessary bits and pieces can be filled in....

[Ruheal Maqsood]

Yes that is what I have done and achieved. Anyways thanks for the accurate post.

[Georg Pauwen]

Do you need the configs ? In the HSRP part, make sure that the primary router LAN interface has a higher priority and has 'standby preempt' configured as well...

[Ruheal Maqsood]

Thankyou for asking. I know the config part.