程序代写 AS 65000 will advertise its 198.133.219.0/24 network to ISP-1 at AS 65001. – cscodehelp代写
Lecture 01: eBGP
HKUSPACE CCIT ENA
Syllabus inspired by Cisco Networking Academy CCNA v7.0 (ENSA)
Module Objectives
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Once you complete this class, you should be able to
•Describe the importance of eBGP protocols •Differentiate iBGP and eBGP protocol. •Configure eBGP protocol on gateway routers.
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IGPs are used to exchange routing information within a company network or an autonomous system (AS).
RIP, EIGRP and OSPF.
Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP)
Used to route between networks administered by two different organizations.
In BGP, every AS is assigned a unique 16-bit or 32-bit AS number which uniquely identifies it on the Internet.
BGP updates are encapsulated over TCP on port 179, inheriting the connection-oriented properties of TCP.
BGP Overview
IGP and EGP Routing Protocols
BGP Overview
eBGP and iBGP
There are two types of BGP:
• External BGP (eBGP) – External BGP is the routing protocol used between routers in different autonomous systems.
• Internal BGP (iBGP) – Internal BGP is the routing protocol used between routers in the same AS.
This course focuses on eBGP.
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BGP Overview
When to use BGP
• The use of BGP is most appropriate when an AS has connections to multiple autonomous systems.
• This is known as multi- homed.
• Before running BGP it is important too have a good understanding of BGP.
BGP Overview BGP Options
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Default route only
ISPs advertise a default route to Company-A. Sub-optimal routing may occur.
This is the simplest method .
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BGP Overview BGP Options
Default route and ISP Routes
ISPs advertises a default route and the ISP networks.
Allows Company-A to forward traffic to the appropriate ISP for networks advertised by that ISP. Sub-optimal routing may occur for networks beyond connected ISPs.
BGP Overview
BGP Options
All Internet routes
ISPs advertises all Internet routes to Company-A.
Allows company to make best routing decisions for all networks. Requires a large number of resources on Company-A routers.
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BGP Overview
Steps to Configure eBGP
To implement eBGP for this course, you will need to complete the following tasks:
Step 1: Enable BGP routing.
Step 2: Configure BGP neighbor(s) (peering).
Step 3: Advertise network(s) originating from this AS
BGP Overview
BGP Sample Configuration
• Using eBGP, Company-A in AS 65000 will advertise its 198.133.219.0/24 network to ISP-1 at AS 65001.
• ISP-1 will advertise a default route in its eBGP updates to Company-A.
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BGP Overview Verify eBGP
• Three commands can be used to verify eBGP.
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BGP Overview Verify eBGP
• show ip ip route shows the output for Company-A’s IPv4 routing table.
• Origin code B identifies that the route was learned using BGP.
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BGP Overview Verify eBGP
• show ip bpg shows the output of Company-A’s BGP table.
• First entry 0.0.0.0 is the default route advertised by ISP-1.
• The second entry 198.133.219.0/24 is the network advertised by the Company-A router to ISP-1.
BGP Overview Verify eBGP
• show ip bgp summary displays the status of BGP connection.
• First line displays the local IPv4 address used to peer with BGP neighbor.
• Last line is the address and AS number of the remote BGP neighbor.
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