Swinog-3, 19 September 2001 IP-Multicast operational experience André Chapuis, IP-Plus

Swinog-3, Multicast operational experience 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

Swinog-3, Multicast operational experience Network layout: MBGP

Swinog-3, Multicast operational experience Network layout: MSDP

Swinog-3, Multicast operational experience 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

Swinog-3, Multicast operational experience 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

Swinog-3, Multicast operational experience 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 count because all the routing tables and forwarding tables were looking fine !  Always check packet-forwarding (once the multicast RT is OK)

Swinog-3, Multicast operational experience Observations/problems i64beb-eng#sh ip mrou count IP Multicast Statistics 207 routes using 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: , Source count: 51, Group pkt count: Source: /32, Forwarding: /44/663/247, Other: /0/0

Swinog-3, Multicast operational experience Debugging  mtrace : uses RPF neighbors up to the source  mtrace : follows SPT for the group  mstat : gives packet-loss along the SPT  show ip mroute count: gives actually forwarded packets  tests from your host !

Swinog-3, Multicast operational experience Mtrace example  i64beb-eng#mtrace  Type escape sequence to abort.  Mtrace from to via group  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 ( )  -1 i64beb-eng-FastEthernet0-0.ip-plus.net ( ) PIM [default]  -2 i64beb-021-atm4-0.ip-plus.net ( ) PIM/MBGP [ /16]  -3 i62beb-031-fas-2-0.ip-plus.net ( ) PIM [ /16]  -4 i64bei-000-Hssi1-0-5.ip-plus.net ( ) PIM/MBGP [ /16]  -5 ges-005-Serial3-1.ip-plus.net ( ) PIM/MBGP [ /16]  -6 lon-000-Serial2-0.ip-plus.net ( ) PIM/MBGP [ /16]  -7 lon-005-POS2-0.ip-plus.net ( ) PIM/MBGP [ /16]  -8 fa0.mcast1.thn.london.eircom.net ( ) PIM [ /29]  -9 fa5-0-0.core1.thn.london.eircom.net ( ) PIM [ /29]  -10 pos1-0-0.core1.cra.dublin.eircom.net ( ) PIM [ /29]  -11 e0.mbone.cra.dublin.eircom.net ( ) PIM [ /29]  -12 dipsy.av.eircom.net ( )  i64beb-eng#

Swinog-3, Multicast operational experience Facts  Global MBGP table contains 3751 entries  IP-Plus currently has 15 multicast peerings  Some popular Websites offer multicast contents: – – (Yahoo, through AS3356 (Level3) –From last week on, Mbone session: –UO internal channel 2 sends CNN live