I need to move a AS to another ISP, although this involves moving several class-C's.
Presently we advertise 3 C classes with a specific carrier. We will be moving all 3 of them to a new carrier, but before this can be accomplished, I need to setup a new router with this new carrier.
The issue I'm having is understanding the impact this will have on the current traffic.
I need to make this as seemless as possible. We have a window of about 1 hour to move production traffic from the current provider to a new provider.
Out of theses 16 c'classes, we will be using 1 of them for the LAN side ou a new 3845. The WAN side will be the peering adress (/30) with the new carrier which we already have.
I need to know what do I have to look for and program in advance (making sure this does not affect current traffic on the current provider) in order to make this seemless as possible.
Thanks for the input.
It will in most cases propagate within minutes.
You could to a point advertise it to your new provider with a very large AS-path prepend. This is how its is done when you run redundant and want to prefer one path over the other.
The risk you take is that you get most the traffic but not all to follow the other path. No matter how hard I have tried I always seem to get some traffic on the so called backup path.
If you work with your new ISP they could tell you how long the AS-path needed to be. You want your new ISP to send all traffic to your old ISP rather than directly to you.
If you get it working this way then you could just turn off the old connection and the new one would take over in less than a minute or in seconds if you get lucky. You could then go back and remove the AS-PATH prepend when you have time to make it more clean.
You have a similar issue on your lan side but since you control all that it is not too hard to adjust the metric to prefer the old path.