[nsp] HSRP and VLANs

[Steffen Voigt]

Hi,

jlewis at lewis.org wrote:

>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?
>  
>
We sucessfully tested the use of hsrp with rfc 1918 space during an ip 
address outage in one subnet
(err... a so called design error ;-) It's working.... as long as you 
have working peer ip's (L3) and they
can see each other...

>  
>
>>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?
> 
>----------------------------------------------------------------------
> Jon Lewis *jlewis at lewis.org*|  I route
> Senior Network Engineer     |  therefore you are
> Atlantic Net                |  
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