SprintLink BGP FAQ
What is BGP?
A. BGP stands for Border Gateway Protocol. Border Gateway Protocol (BGP) is a routing protocol most commonly used between autonomous systems. BGP is a dynamic routing protocol that exchanges routes between BGP neighbors (sometimes called "peers").
How does BGP work?
A. This is a little beyond the scope of this document, however in simplest terms, BGP learns routes from your internal routing protocol (static routes, RIP, OSPF etc.) and announces them to a BGP-speaking neighbor or peer (the Sprint router in this case).
This means that if you are running BGP, you are responsible for your own routing and announcements. Sprint routers learn about your network from your router. Unless you announce the route to us, we cannot send you traffic for that CIDR block. A route announcement is sometimes referred to as a 'prefix'. A prefix announced in BGP consists of the IPV4 or IPV6 address block being announced and also a path of AS numbers, indicating which ASNs the traffic must pass through to reach the announced address block. A BGP prefix would look something like (IPV4): 701 1239 42 The /24 part is referred to as a CIDR mask. The /24 indicates that the first 24 bits in the address block is the ?network? part of the address block.
Do I need BGP?
A. Not unless you are connected to more than one Internet Provider. Static routing is acceptable for most applications, including load balancing.
What do I need to set up BGP?
A. To set up BGP, you need a router capable of running BGP, an official Autonomous System Number assigned through an RIR (Regional Internet Registry, for example ARIN, RIPE or APNIC). Login to Compass and fill out the BGP change request form.
What is an Autonomous System?
A. An autonomous system is one network or series of networks that are all under one administrative control.
What is an Autonomous System Number?
A. An autonomous system number uniquely identifies an autonomous system. These numbers are controlled by IANA, and cannot be randomly selected or configured. You must apply for and receive an AS number from an official RIR (Regional Internet Registry) such as ARIN, RIPE or APNIC before you can start running BGP.
What does "multi-homed" mean?
A. You are "multi-homed" if your network is directly connected to two or more ISP's.
Can I control the preference of my routes within Sprint?
A. Yes. Sprint provides a mechanism for changing the local preference of your routes within the Sprint network. Simply export a community string of 1239:nnn where nnn is the local preference you wish to set for that route. Please see the BGP Policy to view acceptable values.
Can I make Sprint prepend my route(s) to certain Autonomous Systems?
A. Yes. Sprint provides a mechanism for prepending your routes with 1239 to select eBGP peers. Simply send community 6500#:AS, where # is the number of times 1239 will appear in the AS-PATH and AS is the AS to prepend to. Currently, the following ASes are supported: 1668, 209, 2914, 3300, 3356, 3549, 3561, 4635, 6447, 701, 7018, and 702.
Example: AS 123 is a customer of Sprint. They are currently announcing to Sprint. The current AS-Path is "1239 123". AS 123 then tags this advertisement with the following communities: 65000:124, 65002:456, 65003:789, and 65004:1011. This will have the following effects: Sprint will not announce this route ( learned from AS 123 to AS124. Sprint will announce this route ( learned from AS 123 to AS456 with the AS-PATH "1239 1239 123". Sprint will announce this route ( learned from AS 123 to AS789 with the AS-PATH "1239 1239 1239 123". Sprint will announce this route ( learned from AS 123 to AS1011 with the AS-PATH "1239 1239 1239 1239 123".
Can you show me a sample configuration?
A. While the same configuration may not work for all customers, we can provide a list of configuration statements for you to try. For a list of configuration tasks see Cisco's Configuring BGP page.
Cisco router configuration commands for BGP:

	ip subnet-zero

	router bgp [ your AS number ]
	no synchronization
	neighbor [ Sprint router IPV4 IP ] remote-as 1239
	neighbor [ Sprint router IPV4 IP ] version 4
	neighbor [ Sprint router IPV6 IP ] remote-as 1239
	neighbor [ Sprint router IPV6 IP ] version 4
	address-family ipv4 unicast
	network [ Your IPV4 block  ]
	neighbor [ Sprint router IPV4 IP] activate
	neighbor [ Sprint router IPV4 IP ] distribute-list xx out
	address-family ipv6 unicast
	network [ Your IPV6 block  ]
	neighbor [ Sprint router IPV6 IP] activate
	neighbor [ Sprint router IPV6 IP ] prefix-list my_v6_routes out
	no auto-summary

	ip classless

(distribute list configuration statements)
	access-list xx permit [ your IP block ] [ inverse mask ] 
	access-list xx permit (remaining statements)

(prefix-list configuration statements)
	Ipv6 prefix-list my_v6_routes seq 10 permit [Your V6 block]/[prefix length]

It is beyond the scope of this document to discuss configuration specifics. Please see our online BGP policy document for additional information.