Installing a vm on alterway02.ovirt.org

I'm trying to install a VM on alterway02.ovirt.org, but the network seems very unreliable. I gave it 31.15.26.5 and I'm not sure if it's our host, but I often see 89.31.150.107 reply:

From 89.31.150.107: icmp_seq=6 Destination Host Unreachable

This results into some packet loss / errors: 23 packets transmitted, 15 received, +8 errors, 34% packet loss, time 22026ms I thought we could use 31.15.26.1 to 31.15.26.10 so I didn't think I'd steal an IP from another machine. I also tried another IP (31.15.26.6), but that gives the same result. Is there anything I'm doing wrong?