Hardware Forwarding Limitations

Summit family switches, BlackDiamond 8000 series modules, and BlackDiamond X8 series modules can use hardware forwarding when the route mask is 64 bits or less. If the route mask is greater that 64 bits, limitations apply based on the hardware platform.

BlackDiamond 8000 e-series modules, BlackDiamond 8800 c-series modules, and Summit X440, and X460 switches support hardware forwarding for up to 256 routes with masks greater than 64 bits.

This support was added in ExtremeXOS Release 12.4 by using some of the slices previously used for ACL support to create a Greater Than 64 Bit (GT64B) table. The GT64B table stores only those routes with a mask greater than 64 bits. When IPv6 forwarding is enabled, the switch behavior is as follows:

Fewer slices are available for ACLs. The GT64B table consumes 1 slice on BlackDiamond 8800 c-series modules and Summit X440, and 2 slices on BlackDiamond 8000 a- and e-series modules and Summit X460 switches.

To use the GT64B table on X440, one ACL slice must be free. Use show access-list usage acl-slice to check if any slice is unused. If no slice is available, consider disabling a feature that is consuming ACL slices if that feature is not required. Features that are enabled by default such as IGMP Snooping or MLD Snooping can be disabled to free up ACL resources if not required.
Table-full messages appear when there is no more space in the GT64B table.
If an eligible route cannot be added to the GT64B table (because the table is full), there is no guarantee that traffic for that route will be properly routed.
If enabled, route compression for IPv6 can make room for additional routes by reducing the number of entries in the GT64B table.
When an IPv6 address with a mask greater that 64 bits is configured on a VLAN or tunnel, that address is automatically added to the GT64B table.
BlackDiamond 8800 c-series modules do not support hardware forwarding for routes with masks greater than 64 bits on user virtual routers.

BlackDiamond 8900 xl-series modules, and Summit X480 switches support hardware forwarding for up to 245,760 routes with masks greater than 64 bits, depending on the configured setting for external-tables.

BlackDiamond 8900 c- and xm-series modules, and Summit X480, X670, X670-G2, and X770 switches support hardware forwarding for up to 256 routes with masks greater than 64 bits.

This support was added in ExtremeXOS Release 12.4 by using a hardware table designed for this purpose. When IPv6 forwarding is enabled, the switch behavior is as follows:

If no space is available in the hardware table, there is no guarantee that traffic for that route will be properly routed.
If enabled, route compression for IPv6 can make room for additional routes by reducing the number of entries in the hardware table.
When an IPv6 address with a mask greater that 64 bits is configured on a VLAN or tunnel, that address is automatically added to the hardware table.

Published March 2020prev | next

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