Smlt And Ip Routing - Avaya 8600 Configuration Manual

Link aggregation fundamentals

SMLT and IP routing

This section describes SMLT and IP routing interactions.
Navigation
• SMLT and the Virtual Router Redundancy Protocol
• SMLT and VRRP BackupMaster
SMLT and the Virtual Router Redundancy Protocol
Using Virtual Router Redundancy Protocol (VRRP) you can have one active primary router for
each IP subnet, with all other network VRRP interfaces operating in backup mode.
The VRRP has only one active routing interface enabled. Users that access switches
aggregated into two SMLT switches send their shared traffic load (based on source and
destination MAC or IP addresses) on all uplinks towards the SMLT aggregation switches.
The VRRP is less efficient if you use it with SMLT. All other interfaces are in backup (standby)
mode. In this case, all traffic is forwarded over the IST link towards the primary VRRP switch.
All traffic that arrives at the VRRP backup interface is forwarded, so there is not enough
bandwidth on the IST link to carry all the aggregated riser traffic. However, an enhancement
to VRRP overcomes this issue by ensuring that the IST trunk is not used in such a case for
primary data forwarding.
SMLT and VRRP BackupMaster
The VRRP BackupMaster acts as an IP router for packets destined for the logical VRRP IP
address. All traffic is directly routed to the destined subnetwork and not through Layer 2
switches to the VRRP master. This avoids potential limitation in the available interswitch trunk
bandwidth.
To avoid potential frame duplication problems, you can only use the VRRP BackupMaster
feature for SMLT on interfaces that are defined for SMLT. You cannot use VRRP BackupMaster
with hubs to avoid frame duplication or on brouter or VLAN interfaces.
When using an SMLT with routing on SMLT aggregation switches, Avaya recommends that
you use VRRP for default gateway redundancy. In a VRRP environment, one switch is active
and the other is backup. In an SMLT environment, you can enable the VRRP BackupMaster
and use an active–active concept. The VRRP BackupMaster router routes traffic that is
received on the SMLT VLAN and avoid traffic flow across the interswitch trunk. This provides
true load-sharing abilities.
38 Configuration — Link Aggregation, MLT, and SMLT
on page 38
Comments? infodev@avaya.com
on page 38
January 2012