HSRP or ?

[johnelliot6]

Hi,

Have a client that is wanting to implement dual 1841's as the CE's, and use hsrp.

They have 2 upstream connections (1 Wireless(eth) and the other EOC)), both terminate on the same PE in single vrf - Our usual solution for these types of services, is to run ospf on both WANs to our PE, with primary WAN on CE advertising there LAN subnet to us with lower cost than backup WAN, and we only advertise default gw to both...if primary wan goes down, there lan sub is then preferred over backup wan, and there ce receives default route via backup - This is done with single CE(There is no nat happening on CE)

Having very little experience with hsrp, would we somehow be able to implement our "usual" solution, but have the EOC service on the "primary" 1841, and the Wireless WAN service on the "backup" 1841?

I've read you can use object tracking(icmp) in hsrp to check for ip connectivity on wan, so we can failover to the backup 1841, should the primary wan go down, but what happens if the lan interface on the primary goes down? hsrp would kick-in and activate the backup 1841(So LAN traffics default gw would be backup 1841), but the 2 WAN links would still be active, and the primary 1841's ospf would still be telling our PE that it is the prefferred route for there LAN subnet?

In hsrp is the "backup" router still active(i.e. Would ospf still run on wan), or is it in a standby mode?

Is there a better solution to hsrp in this instance?

Thanks in advance.

[Giuseppe Larosa]

Hello John,

>> and the primary 1841's ospf would still be telling our PE that it is the prefferred route for there LAN subnet?

in case the primary router LAN interface fails, the primary CE will stop to advertise the LAN IP subnet in OSPF, by sending out a new router LSA with link state down for the IP subnet associated to the interface.

>> In hsrp is the "backup" router still active(i.e. Would ospf still run on wan), or is it in a standby mode?

HSRP is not a routing protocol it is a first hop redundancy protocol, so OSPF will be up and running on secondary CE and will advertise its router LSA with its increased cost to the internal subnet regardless of HSRP state.

>> I've read you can use object tracking(icmp) in hsrp to check for ip connectivity on wan,

you need to combine object tracking with preemption to be effective and yes it is recommended in your scenario.

you need to enable preemption because it is disabled by default.

You can also consider using standards based VRRP instead of HSRP.

if you want to use the wireless link only when the primary WAN link fails, you shouldn't  use GLBP.

see

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_fhrp_rm_ps6441_TSD_Products_Configuration_Guide_Chapter.html

It will work as it is a quite common scenario.

Hope to help

Giuseppe