How to switch traffic from one ISP to other ISP automatically.

[nilesh.dubey]

Hi Guys,

I got two routers on different location connected through p2p link. There are two ISP providing P2P connectivity. I am running EIGRP both side over p2p line.

Problem-  When an ISP goes down I need manually shut that ISP port to switch complete traffic on other ISP. Is there a way to do it automatically. Whenever any ISP goes down traffic automatically get switched to other ISP.

Thanks,

Nilesh

[Mark Malone]

I would use a loopback as the source not the tunnel interface and leave it as the default tmers 1000 time/3 freq / 2 thres

Have you configured the route-map to work with ip sla it redirect the traffic to the next-hop , when it fails

[nilesh.dubey]

Hi Mark,

Its an old setup and loopback is not defined so I can not use that. I can try physical interface address. Router is not accepting the default timers. Even its not accepting 2000 time/250 tres/ freq 3. Its only accepting above than 6000 time.

I did not configure any route-map. I think it should work without rout-map.

Thanks,

Nilesh

[Mark Malone]

Hi

How would it work though the route-map is the part that redirects the traffic to the next-hop so the ip sla knows where to send traffic otherwise your just pinging a remote ip address ip sla has no routing ability , to change ip sla settings it need to be deleted first you cant change them once there set

The reason I was saying not to use the tunnel is because that's whats going to go down and your taking your ip sla source from it , I would use something that's not part of it , just create local loopback doesn't even need to be advertised just up/up or use a physical

[nilesh.dubey]

Mark,

We use rout-map in IP SLA when we need to got to internet. Its not an internet line. Its a p2p connection for internal traffic only.

Thanks,

Nilesh

[Mark Malone]

The route-map does not care what type of line it is internet /mpls /dsl etc its just redirecting the traffic based on the subnet it matches and its next-hop , this will not work without a route-map ip sla cannot redirect traffic by itself. You still need to redirect your subnet when the ip sla fails and that's where the route-map comes in with the next-hop

[nilesh.dubey]

In route-map which IP should I allow and should I create two different IP SLA for both link or one is enough. Please suggest.

Thanks,

Nilesh

[Mark Malone]

The main objective is when the primary ISP fails you want LAN traffic to redirect out the secondary backup ISP I have that correct yes

1 Create the ip sla and ping something upstream only ISP 1 will know about make sure its working

2 Tie the ip sla into tracking with a route-map.

3 On the route map make sure that any of your subnets you want to switch over when the ip sla fails are included in the matching acl

4 apply the route-map to the interface on router lan  

5 Test the failover between the 2 circuits by dropping the primary link to make sure all LAN traffic switches over and every user is still working

[saashaa747]

Hi Mark,

:

We have 2 ISPs and a Cisco router 2911  , 

I would like to know how to configure the router that a ISP is primary and another ISP is backup 

while the primary ISP work the secondary must not work (standby), so when the primary ISP link is disconnected

the secondary ISP must connect automatically , 

How to configure the router for above scenario ???

[Mark Malone]

If its just 1 router containing both links try this 2 default routes to each ISP , one of them weighted tracking ISP default route 1 which uses ip sla to confirm link is still valid , when it fails to reach 8.8.8.8 it will be removed from rib and then 2nd backup weighted default will go in

ip route 0.0.0.0 0.0.0.0 x.x.x.x track 1

ip route 0.0.0.0 0.0.0.0 x.x.x.x 225 ----This would be the backup ISP as its weighted

track 1 ip sla 1 reachability

Then track a route upstream like below ip sla

ip sla 1
 path-echo 8.8.8.8 source-ip 1.1.1.1
 frequency 5
ip sla schedule 1 life forever start-time now

[paul driver]

Hello

So you are saying presently that your two location are using just the one ISP link. Thus either site A or B routes between the IGP to gain access to the WAN?

or

Do both locations use their respective ISP and route between the IGP for local access?

res
Paul

[nilesh.dubey]

Hello Paul,

Let me explain it again for you.

There are two location connected through p2p link. Like location A an location B and there are two p2p link between A and B. Both p2p link from different ISP. When one link goes down traffic do not automatically switch to other link until I shut the port of down ISP.

Thanks,

Nilesh

[Andrew.Ghorev]

Why just use weight/cost over both links to get one as primary and second as backup? It's more easy than IP SLA... 

    I have more than 20 offices with two links on every. All worked well. I use IS-IS with cost on every link.