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IP-Multicast operational experience

IP-Multicast operational experience. André Chapuis, IP-Plus. Network design. Standard internet protocols PIM-SM MSDP MBGP Redundant RP with anycast-RP Recommended filters for MSDP/PIM ftp://ftpeng.cisco.com/ipmulticast/config-notes/msdp-sa-filter.txt Customer’s RP filtered

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IP-Multicast operational experience

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  1. IP-Multicast operational experience André Chapuis, IP-Plus

  2. Network design • Standard internet protocols • PIM-SM • MSDP • MBGP • Redundant RP with anycast-RP • Recommended filters for MSDP/PIM • ftp://ftpeng.cisco.com/ipmulticast/config-notes/msdp-sa-filter.txt • Customer’s RP filtered • Accept only SA-messages originated by specific RP’s • Congruent IMBGP/IBGP topologies • MBGP only where necessary

  3. Network layout: MBGP

  4. Network layout: MSDP

  5. Observations/problems • MBGP: RPF checks: • IOS 12.0(7)T: MBGP used to leak into the unicast RIB ! • First trial abruptly stopped… • Distance-preferred lookups, not longest-match ! • Problems with aggregates (network statements) • Where to inject prefixes into MBGP if RPF checks are done with network statements rather than IGP route ! • Confed-external IMBGP were set a distance of 20 (bug) • Occurred in IOS 12.0(10)S1 only • Caused routing loops • MBGP/BGP distance needs manual adaptation

  6. Observations/problems • MSDP: peer-RPF checks: • How it works: • When SA-message received, MSDP originator-id is RPF checked with MBGP source AS (to avoid loops when re-transmitting SA-messages) • Issue: • if ISP1 uses parallel MSDP/MBGP peerings and ISP2 only MSDP from its RP: RPF fails • Seen with ‘debug ip msdp’ (use with care !) • Use I-MSDP sessions or mesh-groups to bypass RPF checks

  7. Observations/problems • MDS (Multicast Distributed Switching) bug(?) on IOS 12.0(16.6)S2, Cisco7513, VIP4-80, PA-H, Frame-relay p2p sub-interfaces: • MDS stops forwarding packets after some time (~1min) • Turn off MDS • Could only be seen with sh ip mroute 233.21.90.1 count because all the routing tables and forwarding tables were looking fine ! • Always check packet-forwarding (once the multicast RT is OK)

  8. Observations/problems i64beb-eng#sh ip mrou 159.134.237.179 233.21.90.1 count IP Multicast Statistics 207 routes using 72786 bytes of memory 28 groups, 6.39 average sources per group Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc) Group: 233.21.90.1, Source count: 51, Group pkt count: 234997 Source: 159.134.237.179/32, Forwarding: 226320/44/663/247, Other: 226320/0/0

  9. Debugging • mtrace <group> : uses RPF neighbors up to the source • mtrace <source> <dest> <group>: follows SPT for the group • mstat <source> <dest> <group>: gives packet-loss along the SPT • show ip mroute <group> count: gives actually forwarded packets • http://www.on-the-i.com/mt/index.html: tests from your host !

  10. Mtrace example • i64beb-eng#mtrace 159.134.237.179 195.65.89.1 233.20.90.1 • Type escape sequence to abort. • Mtrace from 159.134.237.179 to 195.65.89.1 via group 233.20.90.1 • From source (dipsy.av.eircom.net) to destination (i64beb-eng-FastEthernet0-0.ip-plus.net) • Querying full reverse path... • 0 i64beb-eng-FastEthernet0-0.ip-plus.net (195.65.89.1) • -1 i64beb-eng-FastEthernet0-0.ip-plus.net (195.65.89.1) PIM [default] • -2 i64beb-021-atm4-0.ip-plus.net (164.128.156.249) PIM/MBGP [159.134.0.0/16] • -3 i62beb-031-fas-2-0.ip-plus.net (164.128.129.230) PIM [159.134.0.0/16] • -4 i64bei-000-Hssi1-0-5.ip-plus.net (164.128.49.13) PIM/MBGP [159.134.0.0/16] • -5 ges-005-Serial3-1.ip-plus.net (164.128.33.129) PIM/MBGP [159.134.0.0/16] • -6 lon-000-Serial2-0.ip-plus.net (164.128.34.14) PIM/MBGP [159.134.0.0/16] • -7 lon-005-POS2-0.ip-plus.net (164.128.33.14) PIM/MBGP [159.134.0.0/16] • -8 fa0.mcast1.thn.london.eircom.net (195.66.230.20) PIM [159.134.237.176/29] • -9 fa5-0-0.core1.thn.london.eircom.net (159.134.191.49) PIM [159.134.237.176/29] • -10 pos1-0-0.core1.cra.dublin.eircom.net (159.134.191.97) PIM [159.134.237.176/29] • -11 e0.mbone.cra.dublin.eircom.net (159.134.192.55) PIM [159.134.237.176/29] • -12 dipsy.av.eircom.net (159.134.237.179) • i64beb-eng#

  11. Facts • Global MBGP table contains 3751 entries • IP-Plus currently has 15 multicast peerings • Some popular Websites offer multicast contents: • www.on-the-i.com • www.broadcast.com (Yahoo, through AS3356 (Level3) • From last week on, Mbone session: • UO internal channel 2 sends CNN live

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