How do I configure Hot Standby Router Protocol (HSRP) to fail over if my WAN interface goes down?

[admin_2]

I have two Cisco routers running Cisco IOS Software 12.0 and 12.1. I have a diverse T, meaning I have separate ISPs for each router. If one ISP goes down, the other ISP is used. This is done with a Border Gateway Protocol (BGP) configuration that the ISP provides for connections.

What I need to accomplish is a fail over on the internal LAN. I need HSRP to fail over if the active router loses its connection to the ISP.

[#2]

The following is the sample configuration for your case:

Assuming RouterA will be the primary gateway for your internal LAN traffic, if it's ethernet card goes down, RouterB will take over to be the gateway of internal LAN. On RouterA, it also monitors the wan link serial interface 1, if it goes down, then the priority gets decemented by 20, so RouterB will take over to be falut tolerant. There is currently no method for HSRP to monitor IP routes, HSRP will only track link failure.

hostname RouterA

!

interface ethernet 0

ip address 1.0.0.1 255.0.0.0

standby 1 ip 1.0.0.3

standby 1 preempt

standby 1 priority 110

standby 1 track serial 1 20

interface serial 1

ip address 20.20.20.1 255.255.255.0

!

The following is the configuration for Router B:

hostname RouterB

!

interface ethernet 0

ip address 1.0.0.2 255.0.0.0

standby 1 ip 1.0.0.3

standby 1 preempt

[layhlaing]

Hi,

Could anyone advise me what should be the gateway for LAN in the above case? Let's say I have a host in the LAN with the ip address of 1.0.0.101/255.0.0.0. Should its gateway be the virtual router ip 1.0.0.3 or the primary router ip 1.0.0.2? I am getting Active on both RouterA and RouterB when show standby is issued.

RouterA#sh standby bri
                   P indicates configured to preempt.
                   |
Interface Grp  Pri P State   Active          Standby         Virtual IP
Vl1       2    100 P Active  local           unknown         1.0.0.3

RouterB#sh standby bri
                    P indicates configured to preempt.
                    |
Interface Grp  Pri P State   Active          Standby         Virtual IP
Vl1       2    110 P Active  local           unknown         1.0.0.3

Thanks to everybody in advance for your sharing.

Regards,

Lay

[Timothy Stewart]

The default gateway for your end devices should be the virtual ip address (1.0.0.3).  If both routers are showing active then that means they do not see each other.  Are the HSRP interfaces on each router connected to the same physical segment (they should be)?

Tim

[layhlaing]

Hi Tim,

Thanks for your input. Both routers can ping each other. HSRP is configured on VLAN interface which is associated with Fastethernet interfaces on each router respectively. The default gateway on my end device is set to be the virtual ip address (1.0.0.3) and it can go out to the internet via that virtual gateway but the issue is that both routers are showing active and HSRP does not work in failing over upon disabling Fastether interface on the primary router.

Regards,

Lay

[Timothy Stewart]

Lay,

Are the fastethernets on both routers physically connected to each other or are they to a switch switch?  They need to be on the same physical segment for the routers to see each other.  Since they are both active, they are not seeing the HSRP hello's.  Please see the following document for more information:

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094afd.shtml

Tim

[layhlaing]

Hi Tim,

It works after putting both on the same physical segment. Thanks for your sharing.

Regards,

Lay

[William Douglass]

If I have two routers with WAN links outbound which are separated by 3 switches, will HSRP work if I setup a VLAN between them?

-how about an OSPF relationship between them? Can HSRP monitor that?

Thanks,

Will