[nsp] HSRP and VLANs

[jlewis at lewis.org]

On Tue, 16 Dec 2003, Marco Matarazzo wrote:

> > As I understand it, you need at least 3 IPs to do HSRP for one subnet
> > or VLAN.  One IP for each physical interface on the router and one
> > virtual IP which becomes the host's default gateway.  By the sounds of
> > it, you may need to expand the subnets for each of those 50 VLANs (if
> > you have promised each customer in the vlan 6 or 14 usable IP
> > addresses, depending) for each  .  I don't know if you can do
> > unnumbered HSRP.

I haven't tried this, but what if you put the real IPs in a different 
subnet (maybe even RFC1918 IPs) and the standby IP in the customer's 
subnet?

> Good point Jason! But I wonder how one can deliver a point to point
> connection (I also have a couple of BGP downstreams) with a  /30, and have
> redundancy... there should been something we missed! At least I hope so! :)

If you mean a PTP T1 or other similar connection, PTP implies there are 
only 2 devices connected.  If you mean a vlan where you used a /30 to give 
yourself (gateway) 1 IP, and the customer 1 IP, then maybe the above idea 
would work.

Is there a limit (other than the number of VLANs a router can support) on 
the number of standby IPs that can be configured?
 
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 Jon Lewis *jlewis at lewis.org*|  I route
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