claro sip trunk routing table

10.0.0.254 (sip trunk gateway)
10.0.0.253 (internet gateway)
172.31.21.1 SIP trunk IP ( this provide signaling)
172.31.21.254 SIP trunk Media Server (This provide audio)

nano /etc/rc.local


/sbin/route add -host 172.31.21.1 gw 10.0.0.254 dev eth0
/sbin/route add -host 172.31.21.254 gw 10.0.0.254 dev eth0
/sbin/route del default gw 10.0.0.254
/sbin/route add default gw 10.0.0.253
/sbin/route add -net 172.31.21.0 netmask 255.255.255.255 gw 10.0.0.254 dev eth0





[root@localhost ~]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.31.21.0     10.0.0.254      255.255.255.255 UGH   0      0        0 eth0
172.31.21.1     10.0.0.254      255.255.255.255 UGH   0      0        0 eth0
172.31.21.254   10.0.0.254      255.255.255.255 UGH   0      0        0 eth0
10.0.0.0        *               255.255.255.0   U     0      0        0 eth0
default         10.0.0.253      0.0.0.0         UG    0      0        0 eth0

Using an IP alias with only one nic

ifconfig eth0:0 192.168.1.100 up  (ip alias)

/sbin/route add -net 172.31.21.1 netmask 255.255.255.255 gw 192.168.1.254 dev eth0:0

/sbin/route add -net 172.31.21.254 netmask 255.255.255.255 gw 192.168.1.254 dev eth0:0