
36
BGP C
ONFIGURATION
BGP Overview
Introduction to BGP
Border gateway protocol (BGP) is a dynamic routing protocol designed to be used
between autonomous systems (AS). An AS is a group of routers that adopt the
same routing policy and belong to the same technical management department.
Four versions of BGP exist: BGP-1 (described in RFC1105), BGP-2 (described in
RFC1163), BGP-3 (described in RFC1267), and BGP-4 (described in RFC1771). As
the actual internet exterior routing protocol standard, BGP-4 is widely employed
between internet service providers (ISP).
n
Unless otherwise noted, BGP in the following sections refers to BGP-4.
BGP is featured by the following.
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Unlike interior gateway protocols (IGP) such as OSPF (open shortest path first),
RIP (routing information field), and so on, BGP is an exterior gateway protocol
(EGP). It does not focus on discovering and computing routes but controlling
the route propagation and choosing the optimal route.
■
BGP uses TCP as the transport layer protocol (with the port number being 179)
to ensure reliability.
■
BGP supports classless inter-domain routing (CIDR).
■
With BGP employed, only the changed routes are propagated. This saves
network bandwidth remarkably and makes it feasible to propagate large
amount of route information across the Internet.
■
The AS path information used in BGP eliminates routing loops thoroughly.
■
In BGP, multiple routing policies are available for filtering and choosing routes
in a flexible way.
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BGP is extendible to allow for new types of networks.
In BGP, the routers that send BGP messages are known as BGP speakers. A BGP
speaker receives and generates new routing information and advertises the
information to other BGP speakers. When a BGP speaker receives a route from
other AS, if the route is better than the existing routes or the route is new to the
BGP speaker, the BGP speaker advertises the route to all other BGP speakers in the
AS it belongs to.
A BGP speaker is known as the peer of another BGP speaker if it exchanges
messages with the latter. A group of correlated peers can form a peer group.
BGP can operate on a router in one of the following forms.
Summary of Contents for Switch 7754
Page 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Page 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Page 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Page 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Page 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Page 126: ...126 CHAPTER 14 SUPER VLAN ...
Page 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Page 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Page 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Page 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Page 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Page 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Page 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Page 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Page 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Page 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Page 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Page 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Page 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Page 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Page 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Page 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Page 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Page 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Page 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Page 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Page 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Page 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Page 718: ...718 CHAPTER 63 CLUSTER ...
Page 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Page 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Page 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Page 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Page 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Page 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Page 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Page 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Page 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Page 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...