To run BGP you are required to have the following:
- An AS Number
- Multi-homed to the Internet
- BGP4 Capable Router
- Sufficient Router Memory
- Fully Functional IGP
- Qualified Internet Engineer
Tutorial: AS Numbers
Originally, an AS number was only available through ARIN. An administrative agreement was worked out so that regional registrars can assign ranges of AS numbers. An AS number can ONLY be purchased from one of the Regional Internet Registries (RIR's). Only certain kinds of organizations qualify to obtain an ASN, such as goverments, global corporations, Internet service providers, telecommunications companies and so forth. An ASN (AS Number) can be requested from one of the registries by filling out an ASN request form (sometimes called the ASN request template) and submitting it to the Which registry you obtain your AS number from is based upon where in the world your network resides physically and will be connecting. This list has expanded to the following registrars:
- AMERICAS - American Registry for Internet Numbers (ARIN)
- AFRICA - African Network Information Center (AFRINIC) - ASN Request Form
- EUROPE - Reseaux IP Europeens (RIPE) - ASN Template
- LATIN AMERICA - Latin American Network Information Center (LACNIC) - ASN Template
- ASIA - Asian Pacific Network Information Center (APNIC)
To receive an AS number from ARIN, RIPE, or APNIC, you must be able to prove your network is connected to more than one Internet Provider running BGP by providing the contact phone number. This is called being 'multi-homed'.
USE A BRAND OF ROUTER YOUR PROVIDER SUPPORTS. This reduces the chances of incompatibility issues and allows your provider to give you better support, as they will have experience with the equipment already.
Cisco routers must be running version 10.3 of the IOS or later to support BGP version 4.
Your router will need sufficient memory to process the BGP routes your providers will be sending you. The table below gives a GENERAL outline of how much RAM will be required. Most providers support most of the following ranges of routes.
| RECEIVING | # | TOTAL RAM REQ'D |
| FULL ROUTES (entire Internet routing table) | ~ 135 K | 128 MB |
| PARTIAL ROUTES | 45 K+ | 64 MB - 128 MB |
| BACKBONE ONLY | 10 - 2K | 32 MB - 64 MB |
| NO ROUTES* | 0 or 1 | -- |
* If you are receiving NO ROUTES from your provider, you will either need a static default route, or ask your provider to send you the default route via BGP. If your ISP uses a Cisco router, your ISP can install the 'neighbor x.x.x.x default-originate' command in their neighbor statements for your BGP session.
Your Interior Gateway Protocol (Static routes, RIP, OSPF, EIGRP) should be completely configured and functionong correctly. ALL internal networks should be completely installed, powered on, and routing correctly internally, as well as having the correct default routes pointing to your soon-to-be-installed Internet BGP4 gateway. Unless these are complete, BGP will NEVER advertise your route unless you take extreme measures, and even then your connectivity to the Internet will likely STILL not work. By default, BGP DOES NOT advertise networks it cannot reach. Thus, an interior IP address range must be fully synchronized with the IP route table before BGP will advertise it to the Internet. You can of course set a Cisco router to use the 'no-synchronization' command, but all that will happen is that traffic will be sent to your Internet router, but your traffic will die right there on the spot unless your Internet router is also the ONLY router on your network and it is directly connected to ALL your networks.
If your company's engineer cannot answer the following questions, have someone who CAN answer these questions configure your BGP:
- What is your AS number?
- What is your router's PUBLIC and ROUTABLE IP address?
- Who are your neighbors and what are their IP addresses?
- What CIDR prefixes will you advertise?
- Will you be aggregating?
- What is your routing policy?
- Will you be accepting full, partial or no routes from your provider?
My advice? Don't let degrees and certificications get in the way of finding qualified personnel. -- InetDaemon