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: Layer 2 switch clustering and SMLT
- Chapter 10: Layer 3 switch clustering and RSMLT
- Chapter 11: Layer 3 switch clustering and multicast SMLT
- Chapter 12: Spanning tree
- Chapter 13: Layer 3 network design
- Chapter 14: SPBM design guidelines
- Chapter 15: 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
- Split-subnet and multicast
- Protocol Independent Multicast-Sparse Mode guidelines
- Protocol Independent Multicast-Source Specific Multicast guidelines
- Multicast for multimedia
- Chapter 16: System and network stability and security
- Chapter 17: QoS design guidelines
- Chapter 18: Layer 1, 2, and 3 design examples
- Glossary
Figure 45: SPBM implementation options
The following sections describe the options that are illustrated in the preceding figure.
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 type-length-value (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 do not require
information about 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.
SPBM design guidelines
98 Network Design Reference for Avaya VSP 4000 Series June 2015
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