Patrick Colbeck wrote: > > It really doesnt matter that there is a whole class B address space as > you should only get arped when someone om the same class B needs to > know your mac address. Once the arping device has your mac address it > should cache it so it doesn't have to arp for it again for a long > time. All the other people on the calls B shouldn't be trying to find > your MAC address as they theoretically should only be talking to your > service providers DSLAM.
Actually it does matter. When Joe user turns off their box it nolonger can answer requests for it's ethernet adderess. This means a bunch of requests for it's arp address. So when someone scans the network you get bombarded by arp requests, and the caches naturally gets trashed durring this. If you know a provider does this you can realy hose up their network by bombarding them with random addresses in their network space. To keep from having this trash a network the router really needs to have enough cache entries to store all hosts on the network. Many routers just can't handle that for a class B network. They really should break their network up into class Cs. > It sounds like somebody has screwed up at the service provider > configuring their routers they have probably:- > > i) Configured a really small arp cache timeout value so the service > provider router is permanatly having to re arp for the mac > addresses of all the DSL modems or > > ii) Configured a static route via a broadcast interface (eg etherent) > on the cental router. This is a really bad thing as instead of just > arping for the next hop address the router will arp every time it > needs to send a packet to any address on the network the route is for > to try and determine the gateway to that address. This is a really > good way to crucify network performance , static routes pointing at > interfaces rather than next hop addresses should only be used on point > t point networks (leased line etc). -- | Bryan Andersen | [EMAIL PROTECTED] | http://www.nerdvest.com | | Buzzwords are like annoying little flies that deserve to be swatted. | | -Bryan Andersen |
