The routing and forwarding table sizes are not part of the public data sheet information.
You will need to contact your reseller or sales engineer for these on an NDA basis but they are readily available via the channel.
With the MX chassis series these vary based on the RE model and memory available primarily. The SCB model and number affect the bandwidth and redundancy of the chassis.
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Steve Puluka BSEET - Juniper Ambassador
IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
http://puluka.com/home
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