Design Reference
Table Of Contents
- Contents
- Chapter 1: Introduction
- Chapter 2: New in this release
- Chapter 3: Network design fundamentals
- Chapter 4: Hardware fundamentals and guidelines
- Chapter 5: Optical routing design
- Chapter 6: Platform redundancy
- Chapter 7: Link redundancy
- Chapter 8: Layer 2 loop prevention
- Chapter 9: Spanning tree
- Chapter 10: Layer 3 network design
- Chapter 11: SPBM design guidelines
- Chapter 12: IP multicast network design
- Multicast and VRF-lite
- Multicast and MultiLink Trunking considerations
- Multicast scalability design rules
- IP multicast address range restrictions
- Multicast MAC address mapping considerations
- Dynamic multicast configuration changes
- IGMPv3 backward compatibility
- IGMP Layer 2 Querier
- TTL in IP multicast packets
- Multicast MAC filtering
- Guidelines for multicast access policies
- Multicast for multimedia
- Chapter 13: System and network stability and security
- Chapter 14: QoS design guidelines
- Chapter 15: Layer 1, 2, and 3 design examples
- Chapter 16: Software scaling capabilities
- Chapter 17: Supported standards, RFCs, and MIBs
- Glossary
Figure 33: SPBM implementation options
A—IP shortcut
IP shortcuts forward standard IP packets over IS-IS. This option enables you to forward IP over
the SPBM core, which is a simpler method than traditional IP routing or MPLS. SPBM nodes
propagate Layer 3 reachability as leaf information in the IS-IS link state packets (LSP) using
Extended IP reachability TLV 135, which contains routing information such as neighbors and
locally configured subnets. SPBM nodes that receive the reachability information use this
information to populate the routes to the announcing nodes. All TLVs announced in the IS-IS
LSPs are grafted onto the shortest path tree (SPT) as leaf nodes.
An IP route lookup is only required once where the source BEB uses the routing table to identify
the BEB closest to the destination subnet. All other nodes perform standard Ethernet switching
based on the existing SPT. This scenario allows for end to end IP-over-Ethernet forwarding
without the need for Address Resolution Protocol (ARP), flooding, or reverse learning. Because
BCB SPBM nodes only forward on the MAC addresses that comprise the B-MAC header, and
because unknown TLVs in IS-IS are relayed to the next hop but ignored locally, SPBM BCB
nodes need not be aware of IP subnets to forward IP traffic. Only BEBs generate and receive
Extended IP reachability TLV to build the routing table; BCBs just relay the TLV to the next
hop based on the SPT. In fact, the Extended IP reachabilty TLV is ignored on BCBs.
With IP shortcuts there are only two IP routing hops (ingress BEB and egress BEB) as the
SPBM backbone acts as a virtualized switching backplane.
IP shortcuts do not require I-SID configuration. However, you must enable IP on IS-IS, and
configure the IS-IS source address to match a circuitless or loopback IP address.
Implementation options
Network Design Reference for Avaya VSP 4000 February 2014 79