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Advertising Multiple NextHop Routes in BGP Joel Halpern Manav Bhatia Paul Jakma 65 th IETF – Dallas, TX.

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Presentation on theme: "Advertising Multiple NextHop Routes in BGP Joel Halpern Manav Bhatia Paul Jakma 65 th IETF – Dallas, TX."— Presentation transcript:

1 Advertising Multiple NextHop Routes in BGP Joel Halpern Manav Bhatia Paul Jakma 65 th IETF – Dallas, TX

2 Applications Persistent route-oscillation conditions in BGP eBGP mesh scaling at IXes Suboptimal Routing in Route Reflector clients Interaction between ECMP capable BGP speakers

3 Multiple Hop Capability | Field | Meaning | Size of field | | | | (octets) | | AFI | Address Family Identifier | 2 | | SAFI | Subsequent Address Family | 1 | | Flags | Multiple-Hop flags | 1 | | Bit: | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | | flag: | R | R | R | R | R | R | R | AE |

4 MULTIPLE_HOP | Address Family Identifier (2 octets) | | Subsequent Address Family Identifier (1 octet) | | Number of Next Hops (1 octet) | | Length of the First Next Hop (1 octet) | | Network Address of First Next Hop (variable) | | Length of the Second Next Hop (1 octet) | | Network Address of Second Next Hop (variable) | |... | | Length of the Nth Next Hop (1 octet) | | Network Address of Nth Next Hop (variable) |

5 How does this work? R1 R2 RR R /8 AS_PATH: X Y NEXT_HOP: N /8 AS_PATH: A B C NEXT_HOP: N /8 AS_PATH: X Y NEXT_HOP: N /8 AS_PATH: A B C MULTIPLE_HOP: N2 *> /8 N2 > /8 N1

6 Removing one of the Routes R1 R2 RR R /8 AS_PATH: X Y NEXT_HOP: N /8 AS_PATH: A B C NEXT_HOP: N2 *> /8 N2 > /8 N1 AS_PATH: A B C MULTIPLE_HOP: N2 WITHDRAWN: /8 *> /8 N1

7 Routes with same Next Hops R1 R2 RR R /8 AS_PATH: X Y NEXT_HOP: N1 LOCAL_PREF: /8 AS_PATH: A B C NEXT_HOP: N1 LOCAL_PREF: /8 AS_PATH: X Y NEXT_HOP: N1 LOCAL_PREF: /8 AS_PATH: A B C MULTIPLE_HOP: N1 LOCAL_PREF: 100 Network Next Hop Metric LocPref Path *>i /8 N1 100 X Y ? * i /8 N1 100 A B C ?

8 Removing one of the routes R1 R2 RR R /8 AS_PATH: X Y NEXT_HOP: N1 LOCAL_PREF: /8 AS_PATH: A B C NEXT_HOP: N1 LOCAL_PREF: 100 AS_PATH: X Y NEXT_HOP: N1 LOCAL_PREF: 100 WITHDRAWN: /8 Network Next Hop Metric LocPref Path *>i /8 N1 100 X Y ? * i /8 N1 100 A B C ? Network Next Hop Metric LocPref Path *> i /8 N1 100 A B C ?


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