[f-nsp] CAM and ip net-aggregate or ip supernet aggregate - does it help to free the cam up ? WAS:AW: cam strangeness

[Stephen J. Wilcox]

On Mon, 6 Mar 2006, Gerald Krause wrote:

> On Monday 06 March 2006 16:48, Gunther Stammwitz wrote:
> > What do the others say: does aggregation help and does the cam
> > usually fill up in an isp enviorment?
> 
>    I do not use aggregation yet but this might be also interesting: I 
> see a lot of /32 CAM entries for destinations that are reachable 
> through a supernet which the router learned via OSPF from two neighbors 
> via two Ethernet links (= 4 equal paths):
> 
> 
> (System: NI4GMR/B2P08000)
> 
> #sh ip route 212.79.18.100
> Total number of IP routes: 180834
>         Destination     NetMask         Gateway         Port Cost Type
>         212.79.0.0      255.255.192.0   212.79.49.135   1/4  20   O
>         212.79.0.0      255.255.192.0  *212.79.49.131   1/4  20   O
>         212.79.0.0      255.255.192.0   212.79.48.3     1/3  20   O
>         212.79.0.0      255.255.192.0   212.79.48.5     1/3  20   O
> #sh cam ip 1/1 | inc 212.79.0.0
> (nothing)
> 
>    but:
> 
> #sh cam ip 1/1 | inc 212.79.18
>   1   8374    212.79.18.198/32  00e0.1e7e.4101    37       1   ether 1/4
>   1   8642     212.79.18.53/32  0050.0b3b.5400   120       1   ether 1/4
>   1   9142     212.79.18.94/32  00e0.1e7e.4101    30       1   ether 1/4
>   1  10131     212.79.18.44/32  0050.0b3b.5470    52       1   ether 1/3
>   1  10601     212.79.18.68/32  00e0.1e7e.4101     7       1   ether 1/4
>   1  11572    212.79.18.100/32  00e0.1e7e.4102   125       1   ether 1/3
> 

i dont see this behaviour on both routers with and without aggregation enabled, 
i checked against routes learned in ospf with 2 or 3 next hops of the same cost

however i do observe /32s being added where the route is to discard (by having a
static 0.0.0.0/0 to null0) - this may explain why my CAM is getting so full

>    Reading the 'Changing CAM Partitions' document on the Foundry website 
> does not really enlighten me - especially "Example 2" looks weird for 
> me. In my opinion the /32's would make sense for directly connected 
> systems or host routes only.... or have I missed something?

yeah i have no idea why they would need to use /32s when simply adding the /30 
and not applying aggregation would be better

Steve