[vserver] multiple IP addresses on one interface

My configuration via kernel 2.6.22.18-vs2.3.0.32.1 on a Centos 5 machine :
 
# ip address show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen
1000
    link/ether 00:15:17:48:fe:ca brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen
100
    link/ether 00:15:17:48:fe:cb brd ff:ff:ff:ff:ff:ff
    inet 77.73.96.155/27 brd 77.73.96.159 scope global eth1
    inet 77.73.96.154/27 brd 77.73.96.159 scope global secondary eth1:1
    inet 77.73.96.156/27 brd 77.73.96.159 scope global secondary eth1:2
    inet6 fe80::215:17ff:fe48:fecb/64 scope link
       valid_lft forever preferred_lft forever
4: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue
    link/ether 5e:0b:75:b9:2e:71 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::5c0b:75ff:feb9:2e71/64 scope link
       valid_lft forever preferred_lft forever
5: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
    link/ether 00:15:17:48:fe:ca brd ff:ff:ff:ff:ff:ff
    inet 192.168.5.1/24 brd 192.168.5.255 scope global br0
    inet 192.168.5.101/24 brd 192.168.5.255 scope global secondary br0:1
    inet6 fe80::215:17ff:fe48:feca/64 scope link
       valid_lft forever preferred_lft forever
 
When I ping to the internet from the host, the source IP used is the default
: 77.73.96.155
 
# tcpdump -i eth1 -n icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
22:26:36.341010 IP 77.73.96.155 > 217.66.0.59: ICMP echo request, id 3339,
seq 1, length 64
22:26:36.356377 IP 217.66.0.59 > 77.73.96.155: ICMP echo reply, id 3339, seq
1, length 64
22:26:37.341338 IP 77.73.96.155 > 217.66.0.59: ICMP echo request, id 3339,
seq 2, length 64
22:26:37.352330 IP 217.66.0.59 > 77.73.96.155: ICMP echo reply, id 3339, seq
2, length 64
 
When I ping to the internet from within the guest, the source IP used is NOT
the default : 77.73.96.154
 
]# tcpdump -i eth1 -n icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
22:29:44.800981 IP 77.73.96.154 > 217.66.0.59: ICMP echo request, id 18955,
seq 1, length 64
22:29:44.813302 IP 217.66.0.59 > 77.73.96.154: ICMP echo reply, id 18955,
seq 1, length 64
22:29:45.801681 IP 77.73.96.154 > 217.66.0.59: ICMP echo request, id 18955,
seq 2, length 64
22:29:45.812003 IP 217.66.0.59 > 77.73.96.154: ICMP echo reply, id 18955,
seq 2, length 64
 
Question : Why is this and secondly, how can I force a guest to either use
77.73.96.154, 77.73.96.155 or 77.73.96.156 ?
 

Thanks in advance !

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