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Cisco Confidential
8
互联神州思科专业技术培训
技术论坛：
一品阳光
TCP—Source/Destination Addresses
10
互联神州思科专业技术培训
技术论坛：
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TCP—Active vs. Passive Session
R1 Opens TCP Session to R2
R1
R2
• Active Session—If the TCP session initiated by R1 is the one used between R1 and R2 then R1 “actively” established the session • Passive Session—For the same scenario R2 “passively” established the session • R1 Actively opened the session • R2 Passively accepted the session • Can be configured
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Cisco Confidential
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互联神州思科专业技术培训
BGP: 2.2.2.2 passive open to 10.1.1.1 BGP: 2.2.2.2 passive open failed - 10.1.1.1 is not update-source Loopback0's address (1.1.1.1)
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Cisco Confidential
7
互联神州思科专业技术培训
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TCP—Source/Destination Addresses
1.1.1.1
R1
2.2.2.2 10.1.1.1 10.1.1.2
成都互联神州思科专业技术培训学校培训网站：
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Cisco Confidential
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互联神州思科专业技术培训
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The Basics
• BGP uses TCP port 179 • Relies on TCP to successfully deliver all BGP messages • Peers exchange OPEN messages which contain basic info such as:
互联神州思科专业技术培训
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边界网关协议 (BGP) 的故障分析
SESSION RST-3254
成都互联神州思科专业技术培训学校培训网站：
Session Number Presentation_ID © 2005 Cisco Systems, Inc. All rights reserved.
Fast Keepalives and Holdtimers
• BGP memory analysis
Why does BGP consume so much memory?
• BGP processes
Explanation of what each process does
• BGP table version
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Cisco Confidential
2
互联神州思科专业技术培训
一品阳光
TCP—Source/Destination Addresses
1.1.1.1
R1
2.2.2.2 10.1.1.1 10.1.1.2
R2
• R1 to R2 connection
neighbor 2.2.2.2 remote-as 100 neighbor 2.2.2.2 update-source loopback 0
Router ID AS # Capabiliate Machine) is used to negotiate Established state • Keepalive/holdtime mechanism ensures peering validity • BGP attempts to open a TCP session to every peer

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互联神州思科专业技术培训
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What Can You Expect?
• BGP peering in excruciating detail ☺
TCP details BGP TCP interaction
• R2 to R1 connection
neighbor 10.1.1.1 remote-as 100 neighbor 10.1.1.1 update-source loopback 0
• R1 and R2 do not agree on what addresses to use
BGP will tear down the TCP session due to the conflict Points out configuration security and adds some 成都互联神州思科专业技术培训学校培训网站： QQ:505836736
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What Do I Expect from You?
• BGP operational experience
Basic configuration Show commands
• Understand the attributes
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TCP—Source/Destination Parameters
• IP Addresses
Destination IP is specified via “neighbor x.x.x.x” Source IP is outbound interface by default Source IP may be specified via “neighbor x.x.x.x updatesource interface”
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BGP/TCP Agenda
• EBGP Multihop Peering • Peering State Machine • Common Mistakes • Troubleshooting commands • Faster Peer Establishment • Flapping Peers • Keepalives and Holdtimers
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• R2 attempts to open a session to R1
BGP: 10.1.1.1 open active, local address 2.2.2.2
• R1 denies the session because of the address mismatch • “debug ip bgp” on R1 shows
• R2 to R1 connection
neighbor 1.1.1.1 remote-as 100 neighbor 1.1.1.1 update-source loopback 0
• Routers agree on source/destination address
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互联神州思科专业技术培训
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neighbor x.x.x.x transport connection-mode [active|passive] 成都互联神州思科专业技术培训学校培训网站： QQ:505836736
Session Number Presentation_ID © 2005 Cisco Systems, Inc. All rights reserved.
• TCP port numbers
Destination will be port 179 Source port is random for added security