Asus Router with Merlin Firmware External Network Interface Alias How To
Asus Router with Merlin Firmware External Network Interface Alias for Cable Modem Management
The external network interface alias is used for obtaining direct access to the cable modem’s management interface when the modem is in bridge modem. A reason for this would be if the cable providers network has some sort of issue that causes externally facing ip on the router to be lost. So the best thing that can be done so a user can view the modem status is to add a dedicated external network interface alias for this subnet that the modem uses. On Ubiquiti/Ubnt routers this feature is known as pseudo ethernet interfaces as noted in my last article.
Example on how to perform this on Asus Merlin Firmware
Enable JFFS if it isn’t already if its enabled create the following script:
/jffs/scripts/services-start
ifconfig `nvram get wan0_ifname`:0 10.0.0.2 netmask 255.255.255.0
iptables -t nat -I POSTROUTING -o `nvram get wan0_ifname` -d 10.0.0.0/24 -j MASQUERADE
The resulting output on the router ifconfig/route information
admin@router:/tmp/home/root# route -n
Kernel IP routing table
Destination   Gateway     Genmask     Flags Metric Ref  Use Iface
24.1.1.0Â Â Â Â 0.0.0.0 Â Â Â Â 255.255.252.0 Â UHÂ Â 0Â Â Â 0Â Â Â Â 0 eth0
10.0.0.0Â Â Â Â 0.0.0.0 Â Â Â Â 255.255.255.0 Â U Â Â 0Â Â Â 0Â Â Â Â 0 eth0
10.54.54.0Â Â Â 0.0.0.0 Â Â Â Â 255.255.255.0 Â U Â Â 0Â Â Â 0Â Â Â Â 0 br0
127.0.0.0 Â Â Â 0.0.0.0 Â Â Â Â 255.0.0.0 Â Â Â U Â Â 0Â Â Â 0Â Â Â Â 0 lo
0.0.0.0 Â Â Â Â 24.1.1.1Â Â Â Â 0.0.0.0 Â Â Â Â UGÂ Â 0Â Â Â 0Â Â Â Â 0 eth0
admin@router:~$ ifconfig -a
eth0   Link encap:Ethernet HWaddr 32:cc:7c:d7:cf:92Â
     inet addr:24.1.1.184 Bcast:255.255.255.255 Mask:255.255.252.0
     inet6 addr: fe80::feec:daff:fe03:6ce3/64 Scope:Link
     UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
     RX packets:155522388 errors:0 dropped:0 overruns:0 frame:0
     TX packets:65604423 errors:0 dropped:0 overruns:0 carrier:0
     collisions:0 txqueuelen:0
     RX bytes:203358201742 (189.3 GiB) TX bytes:17010849276 (15.8 GiB)
eth0:0   Link encap:Ethernet HWaddr 32:cc:7c:d7:cf:92Â
     inet addr:10.0.0.2 Bcast:10.0.0.255 Mask:255.255.255.0
     inet6 addr: fe80::30a8:74ff:fdd7:ef92/64 Scope:Link
     UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
     RX packets:299916 errors:0 dropped:0 overruns:0 frame:0
     TX packets:90592 errors:0 dropped:0 overruns:0 carrier:0
     collisions:0 txqueuelen:0
     RX bytes:52554088 (50.1 MiB) TX bytes:9104214 (8.6 MiB)