If I understand you correctly, you are inquiring if the C10GX GXB TX or RX pins support on-chip termination of 100Ohm. If yes, your understanding is correct.
The C10GX support the following on-chip termination options:
1. TX - 85 Ohm, 100 Ohm
2. RX - tristate, 85 Ohm, 100 Ohm
You may refer to the transceiver PHY user guide and look for "XCVR_C10_TX_TERM_SEL" and "XCVR_C10_RX_TERM_SEL".
Please let me know if there is any concern. Thank you.