ERLITE-3 network problems

I have an ERLITE-3 running NetBSD (NetBSD 9.99.71 (OCTEON) #0: Wed Aug 19 15:36:41 UTC 2020), however I cannot get the network to work.

At the U-Boot prompt I can set the IP address and successfully ping another machine, so the cabling and rest of the network seems ok.

However, even though I can configure an interface in NetBSD I cannot get any packets in or out.  Here is output from a couple of relevant commands:

octeon# ifconfig -a
cnmac0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=0x15500<IP4CSUM_Rx,TCP4CSUM_Rx,UDP4CSUM_Rx,TCP6CSUM_Rx>
        capabilities=0x15500<UDP6CSUM_Rx>
        enabled=0
        ec_capabilities=0x1<VLAN_MTU>
        ec_enabled=0
        address: 18:e8:29:b5:7a:7b
        media: Ethernet autoselect (100baseTX full-duplex,flowcontrol,rxpause,txpause)
        status: active
        inet 10.11.0.130/24 broadcast 10.11.0.255 flags 0
        inet6 fe80::1ae8:29ff:feb5:7a7b%cnmac0/64 flags 0 scopeid 0x1
cnmac1: flags=0x8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500
        capabilities=0x15500<IP4CSUM_Rx,TCP4CSUM_Rx,UDP4CSUM_Rx,TCP6CSUM_Rx>
        capabilities=0x15500<UDP6CSUM_Rx>
        enabled=0
        ec_capabilities=0x1<VLAN_MTU>
        ec_enabled=0
        address: 18:e8:29:b5:7a:7c
        media: Ethernet autoselect (none)
        status: no carrier
cnmac2: flags=0x8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500
        capabilities=0x15500<IP4CSUM_Rx,TCP4CSUM_Rx,UDP4CSUM_Rx,TCP6CSUM_Rx>
        capabilities=0x15500<UDP6CSUM_Rx>
        enabled=0
        ec_capabilities=0x1<VLAN_MTU>
        ec_enabled=0
        address: 18:e8:29:b5:7a:7d
        media: Ethernet autoselect (none)
        status: no carrier
lo0: flags=0x8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33624
        inet 127.0.0.1/8 flags 0
        inet6 ::1/128 flags 0x20<NODAD>
        inet6 fe80::1%lo0/64 flags 0 scopeid 0x4
octeon# netstat -rn -f inet
Routing tables

Internet:
Destination        Gateway            Flags    Refs      Use    Mtu Interface
default            10.11.0.1          UGS         -        -      -  cnmac0
10.11.0/24         link#1             UC          -        -      -  cnmac0
10.11.0.130        link#1             UHl         -        -      -  lo0
127/8              127.0.0.1          UGRS        -        -  33624  lo0
127.0.0.1          lo0                UHl         -        -  33624  lo0
octeon# arp -a
octeon# ping 10.11.0.128
PING 10.11.0.128 (10.11.0.128): 56 data bytes
ping: sendto: Host is down

To my eyes, the configuration all looks normal and is analogous to other NetBSD hosts on the same network.  Are there any known issues with the cnmac driver?  Am I missing something obvious with the configuration?  Debugging suggestions welcome.

Thanks for your help.

Cheers,
Brook