Restrictions And Limitations - Avaya 8800 Planning And Engineering, Network Design

to select the VLAN used for the routed next hop. Migrating the two VLANs one after the
other will reduce the duration for which there is a loss of IGP adjacency.
- Once all the VLANs identified for migration have been assigned an I-SID, the configuration
part of the migration is completed. At this point all the traffic flows should be back to normal.
Related links
SPBM design guidelines

Restrictions and limitations

This section describes the restrictions and limitations associated with SPBM on the Avaya Ethernet
Routing Switch 8800/8600.
STP/RSTP/MSTP
• There is no SPBM support in RSTP mode.
• A C-VLAN-level loop across SPBM NNI ports cannot be detected and needs to be resolved at
the provisional level.
• SPBM NNI ports are not part of the L2 VSN C-VLAN, and BPDUs are not transmitted over the
SPBM tunnel. SPBM can only guarantee loop-free topologies consisting of the NNI ports.
Avaya recommends that you always use SLPP in any SMLT environment.
Note:
Avaya recommends deploying SLPP on C-VLANs to detect loops created by customers in
their access networks. However, SLPP is not required on B-VLANs, and it is not supported.
The B-VLAN active topology is controlled by IS-IS that has loop mitigation and prevention
capabilities built into the protocol.
• SPBM uses STG 63 (with Avaya STP enabled) or MSTI 62 (with MSTP enabled) for internal
use. So STG 63 or MSTI 62 cannot be used by other VLAN/MSTI.
SPBM IS-IS
• SPBM supports IP over IS-IS using IP Shortcuts. However, it does not support RFC 1195.
• SPBM only uses Level 1 IS-IS; it does not support Level 2 IS-IS.
• The IS-IS standard defines wide (32bit ) metrics and narrow (8 bits) metrics. SPBM supports
the wide metric only.
• SPBM supports full High Availability (HA). The SPBM and IS-IS configuration and dynamic
information (such as adjacencies and LSPs) are all HA synced to the standby CPU to ensure
seamless switchover. Since the Ethernet Routing Switch 8800/8600 HA framework cannot
guarantee seamless switchover, there is a 6 to 7 seconds gap between the active CPU going
down and the standby CPU coming up. To avoid IS-IS adjacencies bouncing during the
switchover, the recommended hello interval is 9 seconds and the hello multiple is 3.
Important:
If the switch has a large number of MACs in the VLAN FDB entry table and the primary
SF/CPU fails, it can take longer than 27 seconds for the secondary SF/CPU to become the
June 2016
on page 138
Planning and Engineering — Network Design
Comments on this document? infodev@avaya.com
Restrictions and limitations
169