Download MRIB Multicast Routing Information Base

MRIB
Multicast Routing
Information Base
Site
NREN
PIM-SMv2
MLD snooping,
CGMP…
eMBGP & iMBGP
MLD / IGMP
multicast
applications
Multicast network
topology
ISP’
ISP
Native multicast
All network on the path are multicast enable Æ no problem
Multicast network topology
ISP
Network not supporting multicast
Æ Tunnels required
Multicast tunnels



Logical interface, abstracting underlying infrastructure
Tunnel = logical point to point interface
Multicast packets are encapsulated in unicast packets
IPv4 multicast in IPv4 unicast
 IPv4 multicast dans GRE dans IPv4 unicast
…


A tunnel can be configured almost like any other physical
interface
 Metrics
 Adresses
…
Multicast tunnels
IP multicast packet
IPv4 unicast header
IPv4 multicast
header
Payload
Payload of the unicast packet
Æ Transparent for non multicast routers
Topologies Multicast
• Native
•
•
•
•
•
Much simpler to manage!
No tunnels
Routing is simpler
Troubleshooting is much easier
…
• Not native
• Encapsulation of multicast packets in unicast packets
• Mind the routing protocols (precedence...)
• MTU is smaller
MRIB: Multicast Routing
Information Base
Site A
B
ISP unicast
B
Tunnel
A
A
Routing Information Base (RIB)
Multicast routing Information Base (MRIB)
Site B
MRIB: Multicast Routing
Information Base
• 2 instances of the routing table
• One for unicast routing (RIB)
• One for multicast routing (MRIB)
• Better precedence for MRIB
• Each table must respect the related topology
• Multicast table
• Static routes
• MP-BGP
• Multiprotocol extension for BGP4
• Address family (ipv4, ipv6, ipv4 multicast, ipv6
multicast, mpls …)
Peupler la MRIB
• Static routes
ip mroute prefix mask @dest
• MBGP (Multi-protocol BGP)
router bgp 65051
neighbor 194.254.101.1 remote-as 1717
address family ipv4 multicast
neighbor 194.254.101.1 activate
exit-address-family
• Multi-Topology IGP’s (coming soon !)
• ...
MRIB
• Why ?
• RPF check
• PIM
• MSDP
• When unicast and multicast topologies are
the same, you can forget the MRIB!
• Maybe more appropriate for sites...
PIM & MRIB
• PIM must know where to send (*,G) and
(S,G) joins/prunes
• RPF on * et S to learn interfaces for
sending the messages
• PIM relies completely on the MRIB
MSDP & MRIB
• Can be very comlpex… linked with MBGP !
• Details to come later…
DP
MS
MSDP
PIM MBGP
PIM
GP
B
M
RPF check in reality
•
CISCO :
•
Pas de MRIB per se (arrive bientôt!)
sh ipv6 mrib
•
1.
2.
3.
4.
ne montre pas la MRIB !!!
IPv6 RPF check:
Removes BGP table by default. Can be enabled by ipv6 rpf use-bgp
Longest match over all routing protocols tables (as unicast lookup)
Look also in multicast BGP table and static multicast routes
Break ties using administrative distances
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show ipv6 rpf ipv6-addr
Differences to IPv4 RPF check:
Unicast BGP routes disabled by default
Longest match over all protocols is done. No option to configure it
Recursive lookup is allowed in unicast routing table AND MP-BGP table
Le RPF check en pratique
•
JUNIPER :
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sh multicast rpf inet6 ipv6-addr
MRIB really implemented
Table inet.2 populated with
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MP-BGP
Static routes
For IPv4, RPF is made using inet.2 then inet.0
RPF check et IGP
Routeur B
Loopback = @B
Non-multicast
router
Routeur A
Loopback = @A
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•
Peering iMBGP
A sends prefix P to router B using iMBGP
RPF check for P on router B
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iMBGP says neighbor = @A
Recursive lookup on @A avec IGP...