Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
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Tip
In a design where the receiver is SMLT connected to two egress BEBs, the IGMP receiver
table is automatically synchronized between the BEBs over the IST (or vIST). If a multicast
tree is set up, both egress BEBs will set up a tree, each over one of the available BVLANs.
This ensures that SPB IP Multicast traffic can utilize SPB’s equal cost shortest paths and
multicast stream recovery is sub-second in the event of SMLT BEB or link failure at either
end. (Source SMLT BEBs as well as Receiver SMLT BEBs.)
Multicast Services
The SPB IP Multicast functionality described above can be activated on any of the available VSN service
types already covered:
• IP Multicast over GRT IP Shortcuts: Both Sources and Receivers can exist in the default Global
Routing domain. SPB Multicast is enabled at the IP interface level and need only be activated on the
IP interfaces where sources or receivers exist. Also, if L2 VSN segments are part of the IP Shortcuts
routing domain and IP interfaces (clearly in the same subnet) exist on their BEB end-points, IP
Multicast will automatically be snooped within the L2 VSN as well.
• IP Multicast over L3 VSN: Both Sources and Receivers can exist in VRFs connected to the same L3
VSN. It is not required for the L3 VSN to advertise any IP routes, if the L3 VSN is to be used
exclusively for IP Multicast. SPB Multicast is enabled at the IP interface level and need only be
activated on the IP interfaces where sources or receivers exist. Also, if L2 VSN segments are part of
the L3 VSN routing domain and IP interfaces (clearly in the same subnet) exist on the L2 VSN BEB
end-points, IP Multicast will automatically be snooped within the L2 VSN as well.
• IP Multicast over L2 VSN: Sources and Receivers can only exist within the same L2 segment (and will
thus have IP interfaces in the same subnet). In this case the SPB fabric is only providing an L2 snoop
type functionality. The VLAN used to terminate the L2 VSN service is simply enabled for IGMP
snooping. There need not be any IP address configured on any of the BEBs, though it is advisable to
configure an IGMP query source IP in case non-SPB L2 IGMP-snooping switches are aggregated into
the BEB (otherwise the BEBs will use a 0.0.0.0 source IP in the IGMP Query messages they
transmit).
Where L2 VSNs are IP routed into an L3 domain (L3 VSN or IP Shortcuts), as depicted in Figure 46, there
are clearly two possible ways to activate SPB IP Multicast on them. On the one hand, the L2 VSN BEBs can
simply be IGMP snoop enabled. This will allow IP multicast to be efficiently snooped by SPB within the L2
VSN segment but will result in any IP multicast traffic within that L2 VSN segment being restricted to the L2
VSN alone. In other words, if the L2 VSN is IP routed as part of an L3 domain, no IP multicast traffic will ever
be able to enter or leave the L2 VSN segment. This can be useful in some scenarios but typically is not the
most useful.