Overview Of Bgp4 - Dell PowerConnect B-RX Configuration Manual

Configuring BGP4 (IPv4 and IPv6)

Overview of BGP4

BGP4 is the standard Exterior Gateway Protocol (EGP) used on the Internet to route traffic between
Autonomous Systems (AS) and to maintain loop-free routing. An autonomous system is a collection
of networks that share the same routing and administration characteristics. For example, a
corporate Intranet consisting of several networks under common administrative control might be
considered an AS. The networks in an AS can but do not need to run the same routing protocol to
be in the same AS, nor do they need to be geographically close.
Routers within an AS can use different Interior Gateway Protocols (IGPs) such as RIP and OSPF to
communicate with one another. However, for routers in different ASs to communicate, they need to
use an EGP. BGP4 is the standard EGP used by Internet routers and therefore is the EGP
implemented on the device.
Figure 111
routers. All of the BGP4 routers within an AS communicate using IBGP. BGP4 routers communicate
with other ASs using EBGP. Notice that each of the routers also is running an Interior Gateway
Protocol (IGP). The routers in AS1 are running OSPF and the routers in AS2 are running RIP. The
device can be configured to redistribute routes among BGP4, ISIS, RIP, and OSPF. They also can
redistribute static routes.
FIGURE 111
AS 1
BigIron RX Series Configuration Guide
53-1002253-01
on page 739 shows a simple example of two BGP4 ASs. Each AS contains three BGP4
Example BGP4 ASs
OSPF
IBGP
IBGP
IBGP
OSPF
AS 2
EBGP
RIP
OSPF
RIP
IBGP
IBGP
IBGP
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RIP
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