In message <199608162135.QAA07812@ns1.computek.net>, "Chris MacFarland" writes:
Tim Crowell (GTE.NET) wrote-
GTE has a customer who is a content provider that we have allocated a class C out of our CIDR block.
They have subsequently also ordered a second transit service from ISP XYZ.
I would make them renumber with a new class c that was not in your CIDR block. Maybe they could get a class C from the swamp?
Are you suggesting that all dual homed networks should be renumbered such that they can't be aggregated and can't be reached from a good part of the Internet. I don't think that is a good idea. Are suggesting punishing a customer for picking up a second provider by giving them an unroutable prefix? I hope not.
Our assumptions are: 1. Customer will obtain an AS number to do BGP with both GTE and XYZ. 2. BGP will be established with both ISPs 3. GTE will announce the class 'C' as both a part of our aggregate CIDR block and as a specific /24
No you would just advertise the aggregate CIDR block, they should advertise the more specific route so when you peer with them their route is propagated with their AS number.
I think it is assumed that GTE would be passing on the route heard from the customer. The difference is they would not be passing on the more specific routes they learned from single homed customers in the same blocks, or customer multihomed to them.
4. XYZ will announce the class 'C' as a /24 only.
XYZ should peer with them just as you have done.
Same comment. Announce does not mean "configure a static route".
5. Both GTE and XYZ will supply a default route.
If the client is carrying the full routing table should be default free, if they chose not to then they will have to decide on which provider should be the default route.
There is no harm having a backup. They should not try to load split across the two default routes unless they want extremely poor TCP performance.
It just seems that if there were a large number of these multi-homed Class 'C's that the internet routing table would be flooded. (Maybe thats a part of the problem.
Now you understand why everyone is using Cisco 7500 series routers with 64 to 128 megs of RAM.
I think the percentage of dual homed /24s is small compared to the number of prefixes that have not been aggregated with no good reason at all. Curtis