# Configuring the Switch Fabric Bandwidth

By default, the switch fabric for the Juniper Networks ERX1440, ERX310, E120, and E320 routers uses a bandwidth weighting ratio of 15:2 for multicast-to-unicast weighted round robin (WRR). In the absence of strict-priority traffic, and when both unicast and multicast traffic compete for switch fabric bandwidth, the switch fabric allocates 15/17ths of the available bandwidth to multicast traffic and 2/17ths of the available bandwidth to unicast traffic.

The fabric weights command enables you to specify a ratio for multicast-to-unicast traffic on the router switch fabric. The no version of the command reverts the weighting ratio back to its default.

fabric weights

- Use to define the multicast-to-unicast traffic ratio for the switch fabric for the ERX1440, ERX310, E120, and E320 routers
- Example
  host1(config-traffic-class)# fabric weights multicast 2 unicast 1
- Use the no version to return the switch fabric to its default multicast-to-unicast ratio (15:2).
- See fabric weights.