Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Dynamic Route Failover

Hello,

I am trying to get our network traffic to dynamically pick the best route out/in in case of a link failure. I have attached a diagram showing our current router links. The majority of the links are connected to the end-point routers using wireless backhaul bridges. We have two connections forming a ring back to our central noc. (DS3, and PTP fiber connections). Can any one help with this?

  • LAN Switching and Routing
60 REPLIES
New Member

Re: Dynamic Route Failover

Can you be specific where u want to acheive this.

My suggetion would be you can use HSRP with interface tracking...

New Member

Re: Dynamic Route Failover

Hello,

Any of the router links that go dead, is where I need fail over to take place and re-route customer traffic. Example, router E has three Fe100 interfaces. 1 is directly attached to backhaul bridge, 2 is connected to another backhaul bridge going opposite direction, and 3 would be connected a switch, which feeds various access points which are serving customers for internet access. If INT 1 goes down, I need traffic to route out of INT 2, etc.. Same for all the other connected routers and layer 3 3550.

I do not think all my routers support HSRP, and I am not in a position to upgrade IOS at this time. We have a mixture of static routes, and EIGRP as our routing protocol. All connections eventually terminate at our core 7507 (one is a FE100 interface, the other a serial DS3 connection). We are trying to build a ring to ensure as close to 99% uptime as possible. Also, this got thrown in my lap, so I am a little lost on what to do.

Thanks again for the replies...

New Member

Re: Dynamic Route Failover

Can anyone assist in the HSRP configuration? My routers all support this, but I am not sure the best why to setup the virtual routers, or more importantly on which ones.

In some examle I have read, the Active and Standby virtual routers are residing on the same physical subnet. Do I have to set the routers in this way?

Any help would be appriciated.

Thanks

New Member

Re: Dynamic Route Failover

Hello?

Any sample configurations would be helpful.

Thanks

Re: Dynamic Route Failover

Hi Jesse,

Here's a sample configuration of an HSRP pair:

Both Fa0/1 interfaces are in subnet 192.168.1.0/24 (the LAN of hosts), through which hosts reach remote subnets.

Router 1 and Router 2 are the default gateways for these hosts in a redundant pair.

Router 1:

conf t

interface Fa0/1

ip address 192.168.1.1 255.255.255.0

no shutdown

standby 1 ip 192.168.1.10

standby 1 priority 200

standby 1 preempt

standby 1 track serial0/1 50

Router 2:

conf t

interface Fa0/1

ip address 192.168.1.2 255.255.255.0

no shutdown

standby 1 ip 192.168.1.10

standby 1 priority 180

standby 1 preempt

standby 1 track serial0/1 50

This is probably one of the simplest configurations for interface tracking, that track the state of interfaces serial0/1. You can track multiple interfaces the same way.

Note that ip addresses, interface numbers and standby group number are just examples. You should use your own values.

This will provide you a redundant configuration, but only one HSRP router will be active at a time. So one router will always be idle.

However, you can configure load balancing as well with a symmetrical configuration for standby group 2.

The configuration I provided you makes Router 1 as active and Router 2 as standby.

This is done by setting the priority of Router 1 to 200, which is higher than the priority value of Router 2 of 180.

When interface s0/1 goes down on the active router, interface tracking will lower the priority of the router by 50 (the configured value in the standby track command), so its priority will be 150.

At this time, the priority of the standby router becomes higher (180 configured) and will take over the active role from router 1. This is configured by the standby preempt command.

If interface s0/1 comes up again, router 1 will take over the active role again.

Here's the load balancing symmetrical config:

Router 1:

conf t

interface Fa0/1

standby 2 ip 192.168.1.20

standby 2 priority 180

standby 2 preempt

standby 2 track serial0/1 50

Router 2:

conf t

interface Fa0/1

standby 2 ip 192.168.1.20

standby 2 priority 200

standby 2 preempt

standby 2 track serial0/1 50

In this config router 2 will be active and router 1 will be standby. The takever mechanism is the same: router 1 will take ober from router 2 if interface s0/1 goes down, and take over back if it goes up again.

You need to configure one half of the host PCs with default gateway address 192.168.1.10, the other half with default gateway address 192.168.1.20.

Cheers:

Istvan

New Member

Re: Dynamic Route Failover

Hello Istvan,

I thought I might need to clarify my needs, so I have attached a simpler network diagram. On the attached drawing, I basically need a setup that will allow my network nodes to still route traffic back to our core 7507 router and onto the internet in the event that any of the interface links on routers A, B, or C happen to go down or fail in any way. I am in the process of completing the configuration of EIGRP as our primary routing protocol for route distribution. Behind each router(A,B,or C), I have multiple secondary IP subnets setup serving hundreds of customers.

So if s0/0 fails on Router A, I would need inbound/outbound traffic to route out the interface f0/1 to the next attached router B and so on..

I am not really concerned with load balancing at this time. But redundancy in the event of a link failure is key.

Thanks for any help.

j

Re: Dynamic Route Failover

Hi Jesse,

Sorry for the late response. Today I could free an hour to sit behind the NetPro forum.

The config you provided will give you that failover redundancy you need without HSRP.

If s0/1 goes down on router A EIGRP will automatically use the alternate route through fa0/1 if it is available. And every other router will do the same.

HSRP is needed primarily for default gateway redundancy, though it has a failover feature through interface tracking.

For HSRP you need at least 2 routers for the LAN segment or the VLAN where you want to provide gateway redundancy.

This means you would need 2xRouterA, 2xRouteB, 2xRouterC, just to be simple.

Cheers:

Istvan

New Member

Re: Dynamic Route Failover

Hello,

Would it be possible to get some config assistance for using OSPF on this network diagram. I believe this is what we are moving over to, and I got no experience with this routing protocol. Plus, we are going to be integrating other "non-cisco" devices.

What is confusing me is the multiple areas and stub networks. Or do I even need multiple areas?

anything would be great.

Re: Dynamic Route Failover

Hi Jesse,

Moving to OSPF is a good idea in case you integrate non-cisco devices.

The topology you provided in the Redundant_Project_Simple file, is not so big to be worth bothering with multiple areas at the moment.

Configure all interfaces of all routers for area 0.

Later, if the network grows, then you can use this area 0 as your backbone and expand your network in the locations where your 2950 switches are located now.

Or the number of locations may grow as well, then you can revise the configuration depending on the topology changes.

What is exciting: what is in the NET cloud and how will the OSPF connect to this cloud?

Could you provide info on this?

If you need help in the specific OSPF configurations, please tell me and I will try to post some configs here.

Cheers:

Istvan

458
Views
4
Helpful
60
Replies