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Figure 7-8: Example BGP Network
7.5.1.1.
External BGP Peering
EBGP peering occurs between two or more BGP routers in different AS's. Peer routers in these different AS's
use BGP to maintain a consistent view of the inter-network topology. External BGP peers exchange NLRIs,
which contain reachable network destinations along with BGP specific attributes such as AS path
information and various metrics. These BGP attributes along with local policy configuration, which is used to
filter and/or modify the BGP NLRIs, are used by BGP to determine optimal routes to these network
destinations within the Internet. An illustration of the above scenario can be observed in the figure 31
between routers R2 and R4.
7.5.1.2.
Internal BGP Peering
IBGP peering occurs between two or more BGP routers located within the same AS. Internal BGP peers are
mainly responsible for distributing BGP NLRIs, which have been acquired via External BGP peers, to all other
Internal BGP peers within the AS. The BGP protocol requires that all IBGP peers within an AS are logically
connected as a “full mesh.” Thus, all BGP routers within the AS can have a consistent view of the inter-
network destinations. An illustration of the above scenario can be observed in the figure 31 between
routers R1 and R2.
7.5.1.3.
Advertising Network Layer Reachability Information
In addition to NLRIs exchanged between BGP peers, a BGP router may originate NLRIs for advertisement to
its peers due to local configuration of “locally-originated” routes or “redistribution” policy. In this scenario,
the configuration of locally-originated routes or redistribution policy maps to routes installed in the local
router's forwarding table by IGP routing protocols on the local router. These routes typically define
reachability to network destinations within the local AS. In this manner, BGP is used to advertise NLRIs that
define reachability to network destinations within its own AS to BGP peers outside of the local AS.
Summary of Contents for QuantaMesh QNOS5
Page 1: ...QuantaMesh Ethernet Switch Configuration Guide QNOS5 NOS Platform ...
Page 209: ...209 Table 7 8 IPv6 Neighbor Discovery Settings ...
Page 226: ...226 Table 8 2 L3 Multicast Defaults ...
Page 254: ...254 Appendix A Term and Acronyms Table 9 5 Terms and Acronyms ...