Enterprise BGP Core Network Design - BGP Design and Implementation - page 159

Table 5-1 Router ID Assignment Conventions

Router Name Router ID Router Name Router ID

R1 172.16.1.1 R7 172.16.7.1

R2 172.16.2.1 R8 172.16.8.1

R3 172.16.3.1 R9 172.16.9.1

R4 172.16.4.1 R10 172.16.10.1

R5 172.16.5.1 R11 172.16.11.1

R6 172.16.6.1 R12 172.16.12.1

Internal BGP Core Architecture
The internal BGP core architecture, shown in Figure 5-1, makes use entirely of iBGP
sessions, with no eBGP. The primary benefit of this design is to limit the number of prefixes
carried in the regional IGP domains. However, this design scenario does not provide a clear
delineation between the core resources and the regional resources.

Figure 5-1 Core Architecture Using iBGP

EIGRP 102

R5 R7

R6

R4

EIGRP 103

EIGRP 100
BGP 65100

R8

R1

EIGRP 101

R3

R10

R9

R2

R11

EIGRP 104

R12

The edge of the regional networks and the core network share the same routers. This results
in the core routers running all three routing processes in each region: the regional IGP
process, the core IGP process, and the core BGP process. The region number corresponds