BGP is one of the networking protocol .BGP means Border gateway protocol

1. Border Gateway
Protocol (BGP)
KAREN Technical Workshop
François Prowse
fprowse@juniper.net
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2. BGP Basics
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3. What is BGP?
 BGP is the routing protocol used to advertise routes between
institutions and the KAREN network
 More than just a routing protocol, BGP routes contain many additional
attributes
 Controlled by flexible “Policy” rules that limit what routes we will learn
and what we will advertise
 BGP policy is traditionally used as an interpretation of commercial
arrangements between carriers, ISP’s etc
 BGP can be as simple or as complex as you wish
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4. What RFC’s define BGP?
 RFC 1771 - A Border Gateway Protocol 4 (BGP-4)
 RFC 1772 - Application of the Border Gateway Protocol in the Internet
 RFC 1997 - BGP Communities Attribute
 RFC 1965 - Autonomous System Confederations for BGP
 RFC 1966 - BGP Route Reflection. An alternative to full mesh IBGP
 RFC 2270 - Using a Dedicated AS for Sites Homed to a Single Provider
 RFC 2283 - Multiprotocol Extensions for BGP-4
 RFC 2385 - Protection of BGP Sessions via the TCP MD5 Signature Option
 RFC 2439 - BGP Route Flap Damping
 RFC 2545 - Multiprotocol Extensions for IPv6 Inter-Domain Routing
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5. Routing Protocols
 IGP – Interior Gateway protocol
• Figures optimal path from one node to another node in a network
• Examples include RIP, OSPF, ISIS etc…
• Runs under a single technical/administrative control (AS)
• Can support either IPv4 and/or IPv6
 EGP – Exterior Gateway protocols
• Allows different AS’s to exchange routing information to allow traffic
across two different areas of control
• Only one EGP used in the KAREN network -> BGP
• Policy allows Peers to control routes leant between sites based on
established agreements
• Best practice is to only advertise the routes you wish people to actually
reach.
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6. IGP – Interior Gateway protocol
 Each AS maintains their own IGP
 There is no interaction of IGP’s between any peers in the KAREN
network
 IGP’s are required to allow routing inside a domain
 Examples include
• Static routes
• RIP
• RIPng IPv6 capable
• OSPF
• OSPFv3 IPv6 capable
• ISIS IPv6 capable
• Other proprietary protocols 
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7. EGP – Exterior Gateway protocol
 BGP Can be used in two scenarios
• Internally, inside an Autonomous System
• Known as IBGP (Internal BGP)
• Peers share the same AS number
• Typically implemented as a full mesh
• Typically peer between loopback addresses
• Externally, between peers
• Known as EBGP (External BGP)
• Peers have different AS numbers
• Single point-to-point peering
• Typically peer between interface addresses
 All connections to the KAREN network use EBGP
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8. IBGP – Full mesh, on top of IGP
KAREN Internet
AS 12345
IBGP Peering
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9. EBGP, Peering to the Internet and KAREN
KAREN Internet
AS 12345
EBGP Peering
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10. IBGP and EBGP in operation
KAREN Internet
AS 12345
IBGP Peering
EBGP Peering
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11. BGP Protocol Overview
 BGP Runs over TCP
 Any two routers that have formed a TCP connection to exchange BGP
information are called “Peers” or ‘Neighbors”
 Once connection is made, Peers exchange their full BGP routing tables.
 Updates are then sent as the table changes or new routes are added to the
network.
 BGP peers in the KAREN network should be capable of exhanging both IPv4
and IPv6 routes
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12. BGP Routes
 BGP routes contain more that just the advertised prefix
• Origin
• AS Path
• Next Hop
• Local Preference
• Multiple Exit Discriminator
• Community
 BGP Policy looks at the prefix as well as route attributes for decision making
 BGP attributes can often be changed to influence downstream policy
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13. Autonomous System
 Autonomous System (AS)
• Group of routers belonging to a single administrative domain
• Viewed externally as a single, coherent interior routing domain
• Each AS runs their own chosen IGP
 AS Numbers
• Public and private AS numbers are available for use
• Public numbers assigned locally by APNIC to each institution
• Larger tertiary institutions potentially already have one assigned
 You will need a Publicly Assigned AS number to connect to KAREN!
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14. BGP Policy
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15. BGP Policy
 BGP Policy controls what BGP routes are installed in the routers routing table
and what routes are advertised to your peers
 Use BGP policy when
• You don’t want to import all learned routes into the routing table
• You don’t want to advertise all known routes to neighboring routers
• You want BGP to receive routes from another protocol (Redistribution)
• You want to modify information (BGP Attributes) associated with routes
 BGP Policy configuration varies with each router vendor and platform
 BGP Policy can be as simple or as complex as you wish
 Ensure your routers policy implementation is as flexible as possible
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16. Default Policy
 BGP when left to its own devices will fall back to default policy for the import
and export of routes.
 Can vary with vendor implementation
 Import
• All routes learned from BGP neighbors are installed in the routing table
 Export
• Transmit all routes learned from BGP neighbors to all BGP neighbors
• Advertise only active route
 If you aren’t running IBGP in your network then you will need policy to
redistribute IGP routes to KAREN
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17. Import and Export Policy
 Control the flow of routes between your network and KAREN by creating
specific policy rules!
 Import Policy
• Apply an import routing policy to control the routes that the routing protocol
process uses to determine active routes
• Affects routes that BGP receives from a neighbor
• Modify BGP attributes
 Export Policy
• Apply an export routing policy to control the routes that a BGP router advertises to
its neighbor
• Modify BGP attributes
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18. Why do we need policy
200.0.0.0/24
192.168.0.0/24
KAREN Internet
AS 12345
200.0.0.0/24 200.0.0.0/24
192.168.0.0/24 192.168.0.0/24
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19. Policy enforcement
Export Export
Import Import
KAREN Internet
AS38022
AS 12345
Eg.
Eg.
Filter all RFC 1918 routes
Import all AS38022 routes No export AS38022 routes
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20. Platform requirements
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21. Router requirements
 BGP peers in the KAREN network will be expected to perform the following
• BGP peering of both IPv4 and IPv6, large number of routes
• While the Internet is currently 160K+ routes, KAREN “should” be smaller
• Forwarding of Ethernet Jumbo Frames
• Interdomain Multicast forwarding
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22. Router requirements
 Not all routers capable of the demands required
• Does my platform of choice support all the relevant RFC’s?
• Pay attention to maximum number of routes in Routing table and Forwarding Table
for both IPv4 and IPv6
• Is the router forwarding in Software or Hardware?
• Do Jumbo Frames limit my forwarding performance, while mixed with smaller
packets?
• Is there a flexible “Policy” implementation to control routes installed in route
table
• What are the default Policies of BGP
• Is there any additional Security I should be concerned about?
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23. More Information and
Help?
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24. More Information…
 Books
Practical BGP BGP Illustrated JunOS Cookbook
ISBN 0321127005 ISBN 0596002548 ISBN 0596100140
 RFC’s
• Specifically RFC 1771, 1772 and 1997
 Online
• http://www.bgp4.as
• http://www.juniper.net/techpubs/software/junos/junos80/swconfig80-routing/frameset.htm
 Vendors, Consultants and your existing ISP
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25. Q & A?
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26. Thank You