[c-nsp] HSRP and removing connected route

Jay Nakamura zeusdadog at gmail.com
Thu Dec 8 18:12:17 EST 2011

On Thu, Dec 8, 2011 at 4:44 PM, Jay Hennigan <jay at west.net> wrote:
> On 12/8/11 12:23 PM, Jay Nakamura wrote:
>> So, the situation is this.
>> Let's say I have a topology where there are two routers, each router
>> connected to separate switches, and the two switches are connected to
>> a gigabit ethernet WAN.
> Just to each other or to other resources on the WAN?

So, router A <-> switch C <-- WAN --> switch D <-> router B

Router A & switch C is in city X
Router B & switch D is in city Y

Router A and Router B has upstream connection out the internet.

>> One router and switch is in one city, other router and switch is in
>> another city.
>> There is a VLAN that spans the two routers, two switches and servers
>> hosted in one city.
> Somewhat confused here, as previously you indicated that there was one
> router/switch pair in each city.  Or is it router/switch A along with
> servers in city A and router/switch B in city B that wants to reach the
> servers in city A?

Did the above explanation help with this question?

>> I have the VLAN on HSRP between the two routers.
>> The problem is this.  When the gigabit WAN goes down, the one end of
>> the router without the host will still try to route that traffic out
>> it's VLAN.  Is there a way to prevent that by using IP SLA or track
>> command or some other trick?  Perhaps shutdown the subinterface auto
>> magically?  (Although, if it shuts it down, I am not sure how it will
>> detect that the service is back up)
> Is there a backup route via another path for the orphaned remote city to
> reach the servers?

There is through upstream connectivity to the internet.  But the route
it would have will be the default route so the more specific connected
route would be followed in City Y.

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