Hi Gunther, the problem wasnt just the cam filling, once it was full instead of ageing out an entry and installing a new entry for the requested route it is matching anything else in the CAM.
eg i sent a packet to 10.10.10.10 i have a route 10.10.10.0/24 to go out of port 1 - this is not in the CAM i have a route 10.10.0.0/16 to go out of port 2 - this is in the CAM we expect to incur a cache miss and install the /24, instead the cache matches the /16 and the packet is sent the wrong way in Kristian's case, he was seeing matches to 0.0.0.0/0 to null0 matching where no CAM entry was found and the packet was dropped when there was a valid route in the routing table Steve On Mon, 6 Mar 2006, Gunther Stammwitz wrote: > Hello Kristian, > > That sounds horrible! Didn't you open a case with TAC/technical-support? > Which management module exactly are you using? Is it ironcore or jetcore and > what are your settings regarding the cam-partition, the supernet-aggregation > and the ip net-aggregate? > > > I have seen some strange behaviour too on our jetcore-module: > When enabling the ip supernet aggregate-command which the cpuload jumped > from 10 to 20 or even 25% so we disabled it again. The interestint thing was > that the cam was freed up to ~50% or something like that. > > The next try was to enable ip net-aggregate and the load jumped from 10% to > 99 which was rather bad and caused a lot of packet loss and so on > (Trouble!). The solutions was to use ip net-aggregate X where X is a number > of let's say 10 or 30 so that the aggregation-process won't try to compres > the cam every one second which is the default behaviour but rather every 10 > or maybe even 30 seconds. > This reduced the load to 5% and we can't even notice the aggregation-process > that should run from time to time. No packetloss no nothing > > Our current cam-usage is looking like this: > #show cam ip 1/1 stat > CAM IP statistics: free entries total entries > level1: 8670 28672 > level2: 1147 2048 > level3: 1960 2047 > I'm not really sure that it was before but I think to remember that without > any aggregation at all there were about 20000 entries (layer1) free but I'm > not sure. We're using bgp with 3 full views. > > On another router that I'm managing there's a ironcore mgmt-card, 2 full > bgp-views and some peers and most of the traffic is following the default > route and the usage is looking like this: > show cam ip 1/1 stat > CAM IP statistics: free entries total entries > level1: 4072 8192 > level2: 1726 2048 > level3: 2020 2047 > > > What do the others say: does aggregation help and does the cam usually fill > up in an isp enviorment? > What about situation with gameserver-providers or voip which causes a lot of > connections? > > Gunther > >
