Web OS 10.0 Application Guide36 n Chapter 1: Basic IP Routing 212777-A, February 2002Border Gateway Protocol (BGP)Border Gateway Protocol (BGP) is an Internet protocol that enables routers on a network toshare and advertise routing information with each other about the segments of the IP addressspace they can access within their network and with routers on external networks. BGP allowsyou to decide what is the “best” route for a packet to take from your network to a destinationon another network rather than simply setting a default route from your border router(s) to yourupstream provider(s). BGP is defined in RFC 1771.Alteon Web switches can advertise their IP interfaces and virtual server IP addresses usingBGP and take BGP feeds from as many as four BGP router peers. This allows more resilienceand flexibility in balancing traffic from the Internet.Internal Routing Versus External RoutingTo ensure effective processing of network traffic, every router on your network needs to knowhow to send a packet (directly or indirectly) to any other location/destination in your network.This is referred to as internal routing and can be done with static routes or using active, inter-nal routing protocols, such as RIP, RIPv2, and OSPF.It is also useful to tell routers outside your network (upstream providers or peers) about theroutes you can access in your network. External networks (those outside your own) that areunder the same administrative control are referred to as autonomous systems (AS). Sharing ofrouting information between autonomous systems is known as external routing.External BGP (eBGP) is used to exchange routes between different autonomous systemswhereas internal BGP (iBGP) is used to exchange routes within the same autonomous system.An iBGP is a type of internal routing protocol you can use to do active routing inside your net-work. It also carries AS path information, which is important when you are an ISP or doingBGP transit.N OTE – The iBGP peers must be part of a fully meshed network, as shown in Figure 1-3.
