Try setting promiscuous mode
Xircom PCMCIA Ethernet Adapter Issues
Can anyone advise a newbie on getting RBEN56G working ? (Gordon Licence)
Newbie advise for Xircom RBEM56G (Alberto Gonzalez Palomo)
Same problem (Vincent Nijs)
Date: 2000, Jun 12
From: David Hinds <email@example.com>
ifconfig eth0 promisc
and see if things start working after that. Whether the card is
recognized as CBEM or RBEM should be irrelevant.
to: "Try setting promiscuous mode"