On Mar 26, 2008, at 3:08 PM, Timothy Selivanow wrote: > The only way to "shotgun" (an ISP had to specifically support modem > shotgunning in the olden days, BTW), i.e. do aggregate routing, is if > you had a separate routed sub-net and ran BGP on the router > connected to > the two lines (The rest of the internet has to know that you have two > lines and both are available to use, concurrently). Needless to say, > this can be complicated, and is not considered a "consumer" setup > (most > providers will require it to be some sort of business type connection > like, T and OC connections, which can be on the order of thousands a > month, hundreds for a "fractional" T connection). If you are connecting to the same ISP with your lines, there's no need for BGP. (Yes, I know about the cases when the ISP could use BGP for various good reasons, but those are far outside the scope of "shotgun" type connections.) The "shotgun" schemes and ISDN bonding are usually implemented with proprietary or standards based multilink PPP setups. There are also devices like inverse muxes that will allow you to bond T1s or E1s together for higher speeds on serial or Ethernet interfaces. Most modern routers also support ECMP (Equal Cost Multi Path) which will spread your traffic over two or more links between the same pair of routers. The paths can be T or E carriers, Sonet, Ethernet, etc. BGP comes into play when you need to make the rest of the Internet aware that you are connected (multihomed) to two or more transit carriers. Running BGP requires that you have reasonably serious routing hardware and reasonably large amounts of IP address space, and lots of clue. This is way off topic at this point, and should probably be dropped. --Chris