In smaller service provider networks, or those who do not cater to many
large BGP customers, an oft-used practice is to configure eBGP-multihop
between your customer and the nearest BGP router in your (SP) network.
Obviously, the problem is that packets must be routed through the non-BGP
edge device. This can be achieved in several ways but the simplest in many
SP environments is to use defaults from your non-BGP edge box to your
(presumably) BGP core, through which packets can be routed to the BGP exit
point (peer/other BGP customer/transit.) The tricky bit is the reverse
path, which can most simply be done again with statics redistributed into
IGP on the edge aggregation device pointing to the customer (for the bgp
routes the customer advertises to you.) In the event that the customer is
large enough to advertise a lot of prefixes to you then the amount of
bandwidth they should push, just upgrade your kit :)
Damon
Carrier1
> -----Original Message-----
> From: Elijah Kagan [mailto:elijah@netvision.net.il]
> Sent: 03 October 2001 15:26
> To: cisco-nsp@puck.nether.net
> Subject: Supplying full BGP table to customers
>
>
> Hi Everybody,
>
> I have a question about ways of supplying full Internet
> routing table to
> customers.
>
> Lately, each and every customer of ours wants us to supply
> them the full
> Internet routing table via BGP, even those customers that
> have 0.005 bps
> of bandwidth. The problem is that not all of our poor 7200 acting as
> customer aggregation routers can handle that kind of routing
> table without
> major memory upgrade.
>
> I was wondering whether people use route servers for the task
> of suppling
> full routing table to customers?
>
> I'll expand on that. A customers connects to an aggregation router as
> usual and establishes a BGP session with it. This session is
> used only to
> advertise customer's and our prefixes. Another BGP session is
> established, this time between a customer and a route server. Customer
> then receives full routing table and route server takes care
> not to learn
> anything from that customer. This installation reduces the amount of
> memory needed by an aggregation router to the minimum.
>
> I'd like to hear some comments regarding the above configuration. Are
> there any common techniques of supplying full routing table except the
> obvious?
>
> Thanks,
>
> Elijah
>
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