VLAN%20Mapping%20and%20TRILL

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VLAN Mapping and TRILL

• Radia Perlman
• Radia.Perlman_at_sun.com

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Issue

• Bridges currently do VLAN mapping

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Issue

• Bridges currently do VLAN mapping
• Intentionally, even

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Why?

• Merge two clouds
• VLAN A in one cloud means something different
  from VLAN A in another cloud
• VLAN A in one cloud should be the same as VLAN
  B in the other cloud
• Separate a community
• (perhaps) make VLAN A into two communities
  (topology has to be cooperative)

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What we want

• We want only RBridges connecting the two clouds
  to have any notion this is going on

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RB1
RB2
west
east
RB3
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Configure ports
RB1
RB2
west
east
RB3
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RB1, RB2, and RB3 know (East, VLAN A) (West,
VLAN B)
RB1
RB2
west
east
RB3
When forwarding data between East and West,
change the (inner) VLAN tag
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Other nits

• ESADI about VLAN A endnodes tagged by using
  (inner) VLAN tagA
• So VLAN A ESADI turns into VLAN B ESADI as it is
  forwarded from East to West
• To detect misconfiguration cut set RBridge MAY
  announce its mappings in its LSP

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Other nits, contd

• If RB1 is configured to map (East, VLAN A) to
  (West, VLAN B), then RB1 MUST announce (in RB1s
  LSP) that RB1 is attached to both VLAN A and VLAN
  B (regardless of whether RB1 is appointed
  forwarder for anything)
• The reason for this is so that, e.g., multicast
  for VLAN A originating in West will get to RB1

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Multicast groups

• RB1 MUST do one of the following
• Enumerate all (East, VLAN A) groups as being VLAN
  B groups attached to RB1 (in RB1s LSP)
• Announce that RB1 has an IPv4 and IPv6 multicast
  router in VLAN B attached to RB1 (in RB1s LSP)