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
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