Radware Alteon, Инструкция по применению

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Document ID: RDWR-ALOS-V2900_AG1302
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Chapter 10 – Border Gateway Protocol
The Border Gateway Protocol (BGP) enables routers on a network to share and advertise routing
information with each other about the segments of the IP address space they can access within their
network, and with routers on external networks. BGP allows you to decide what is the "best" route
for a packet to take from your network to a destination on another network, rather than simply
setting a default route from your border routers to your upstream providers. BGP is defined in RFC
1771.
Alteon can advertise its IP interfaces and virtual server IP addresses using BGP and take BGP feeds
from as many as 16 BGP router peers. This allows more resilience and flexibility in balancing traffic
from the Internet.
The following topics are addressed in this chapter:
• Internal Routing Versus External Routing, page 125
• Forming BGP Peer Routers, page 126
• Route Maps, page 126
• Aggregating Routes, page 129
• Redistributing Routes, page 130
• BGP Attributes, page 130
• Selecting Route Paths in BGP, page 131
• BGP Failover Configuration, page 131
• Default Redistribution and Route Aggregation Example, page 134
BGP-based Global Server Load Balancing (GSLB) uses the Internet's routing protocols to localize
content delivery to the most efficient and consistent site. For more information on BGP-based GSLB,
see
Using Border Gateway Protocol for GSLB, page 758 .
Internal Routing Versus External Routing
To ensure effective processing of network traffic, every router on your network needs to be
configured to correctly send a packet (directly or indirectly) to any other location or destination in
your network. This is referred to as internal routing, and can be done with static routes or using
active internal dynamic routing protocols, such as the Routing Information Protocol (RIP), RIPv2,
and the Open Shortest Path First (OSPF) protocol.
Static routes should have a higher degree of precedence than dynamic routing protocols. If the
destination route is not in the route cache, then the packets are forwarded to the default gateway,
which may be incorrect if a dynamic routing protocol is enabled.
It is also useful to expose the routes you can access in your network to routers outside your network
(upstream providers, or peers). External networks (those outside your own) that are under the
same administrative control, are referred to as autonomous systems (AS). Sharing of routing
information between autonomous systems is known as external routing.
External BGP (eBGP) is used to exchange routes between different autonomous systems, while
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 perform active routing inside your network. It also
carries AS path information, which is important when you are an ISP or performing BGP transit.
The iBGP peers must be part of a fully meshed network, as shown in
Figure 13 - Example Topology
using the Border Gateway Protocol (BGP), page 126 :