10G ETHERNET MAC IP -10GBase-R Design example

Hello,

In 10G E MAC example design which is available in Altera/IP/Ethernet/altera_eth_10g_design_example/altera_eth_10g_mac_base_r.

In this example design 10G E MAC and 10G BASE-R Phy are used and if you observe in this document "https://www.altera.com/content/dam/altera-www/global/en_US/pdfs/literature/ug/10gbps_mac.pdf" page number 24, there are two PHY's.

1. 10G BASE-R PHY/ XAUI PHY

2.External PHY

I'M confused with this External PHY. In the design example already there is 10GBASE -R PHY with 10G-EMAC, but why this External PHY is used.

Please let me know the application of this external PHY.

regards

Vinod