BGP Overview
351
■
Version: BGP version. As for BGP-4, the value is 4.
■
My Autonomous System: Local AS number. By comparing this filed of both
sides, a router can determine whether the connection between itself and the
BGP peer is of EBGP or IBGP.
■
Hold time: Hold time is to be determined when two BGP speakers negotiate for
the connection between them. The Hold times of two BGP peers are the same.
A BGP speaker considers the connection between itself and its BGP peer to be
terminated if it receives no Keepalive or Update message from its BGP peer
during the hold time.
■
BGP Identifier: The IP address of a BGP router.
■
Opt Parm Len: The length of the optional parameters. A value of 0 indicates no
optional parameter is used.
■
Optional Parameters: Optional parameters used for BGP authentication or
multi-protocol extensions.
Update
Update message is used to exchange routing information among BGP peers. It can
propagate a reachable route or withdraw multiple pieces of unreachable routes.
Figure 82 shows the format of an Update message.
Figure 82
BGP Update message format
An Update message can advertise a group of reachable routes with the same path
attribute. These routes are set in the NLRI field. The Path Attributes field carries the
attributes of these routes, according to which BGP chooses routes. An Update
message can also carry multiple unreachable routes. The withdrawn routes are set
in the Withdrawn Routes field.
The fields of an Update message are described as follows.
■
Unfeasible Routes Length: Length (in bytes) of the unreachable routes field. A
value of 0 indicates that there is no Withdrawn Routes filed in the message.
■
Withdrawn Routes: Unreachable route list.
■
Total Path Attribute Length: Length (in bytes) of the Path Attributes field. A
value of 0 indicates that there is no Path Attributes filed in the message.
■
Path Attributes: Attributes list of all the paths related to NLRI. Each path
attribute is a TLV (Type-Length-Value) triplet. In BGP, loop avoidance, routing,
and protocol extensions are implemented through these attribute values.
■
NLRI (Network Layer Reachability Information): Contains the information such
reachable route suffix and the corresponding suffix length.
0
15
31
Total Path Attribute Length
Withdrawn Routes(Variable)
Path Attributes(Variable)
NLRI(Variable)
Unfeasible Routes Length
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 ...