can't remember what ip address of a router set up as an access point is

i tried to set up my belkin n+ router as an access point a month ago, but failed, and regrettably failed after i had set it's ip address, which i can't remember. so now it appears bricked, as i don't know how to login to it via web interface from its ip address. hard resetting the router didn't work (tried all methods, 30/30/30, etc.). any suggestions how to find out what the router's ip address is to un-brick it?

fyi i have seen this: Can't find a wireless access point's IP address after changing router IP/LAN settings and it didn't get me anywhere

jason

Posted 2015-01-06T03:27:46.573

Reputation: 11

Does it have an inbuilt DHCP server that's running? i.e. if you connect to it's Wifi or Ethernet, do you get it serve you IP addresses? Can you tell us what the model name is? – LuckySpoon – 2015-01-06T03:33:03.977

It's a Belkin N+ F5D8236-4 – jason – 2015-01-06T03:53:35.460

don't know if it has an inbuilt dhcp server. when i connected it via ethernet to my laptop and ran ipconfig, my laptop showed an ipv4 address of 169.254.0.23 and a subnet mask of 255.255.0.0. these numbers seem very odd to me, as i use comcast so my gateway is normally 10.0.0.1 with 255.255.255.0 subnet mask. – jason – 2015-01-06T04:34:07.053

The 169.254.0.0/16 range is reserved for autoconfiguration; a machine that doesn't use DHCP or can't find DHCP will select an address in the region more or less randomly. Since your laptop picked an address in that range, the router isn't providing DHCP service to your laptop. You might try scanning that range with nmap, too, to see if the router autoconfigured itself. – Fred – 2015-01-06T05:00:19.113

running -sP 169.254.0.0/16 now – jason – 2015-01-06T05:11:18.680

ran -sP 169.254.0.0/16, said host is up for 169.254.92.173 and .176.107, but can't access the AP router through these IPs. will see what else shows as a host tomorrow when i wake up. thanks for the help so far. – jason – 2015-01-06T05:41:42.043

One more thing, if you are looking for a web interface, look for an open port 80 (http:) or 443 (https:). nmap -p 80 169.254.0.0/16 for example. – Fred – 2015-01-06T15:22:03.130

ran -sP 169.254.0.0/16 this morning, got 4 hosts (.92.173, .220.23, .235.4, .245.218) but none worked to access the AP router's web interface. trying to look for an open port now, as suggested – jason – 2015-01-06T16:41:42.977

nmap -p 80 169.254.0.0/16 showed the same 4 hosts as above, each with "80/tcp unknown http" (and still none of these 4 allow the web interface). trying port 443 now – jason – 2015-01-06T17:30:40.287

Answers

I'd try the DHCP approach above, but if you hadn't configured the AP to act as a DHCP server, all is not lost. If you set up the AP in private address space, you can use something like nmap to scan the range of likely IP addresses, especially if you can remember the range you used. The private IP ranges are 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. See if you can ping the router and learn the IP.

Fred

Posted 2015-01-06T03:27:46.573

Reputation: 1 205

i thought i had tried running nmap (and arp command), but didn't get anywhere. could you possibly walk me through it? – jason – 2015-01-06T04:39:49.433

1Sure. Do you have any idea which address range you used? You can use nmap to do a host discovery (ping) scan as follows: nmap -sP 192.168.1.0/24 to scan the 192.168.1.0/24 network. – Fred – 2015-01-06T04:44:40.180

i could've sworn i used 10.0.0.255, but i'm not sure. – jason – 2015-01-06T04:46:13.170

just to confirm, i'm running nmap on a computer that is hooked up via ethernet to a lan port on the bricked router. – jason – 2015-01-06T04:47:02.490

Then try 10.0.0.0/24 for starters. If you don't find it there, use a /16, but it will take a lot longer.

Yes, the LAN port should be in the private address range the AP is serving. – Fred – 2015-01-06T04:47:16.287

nmap 10.0.0.0/24 failed on all numbers .0 to .255, except for 10.0.0.2 however, i can't login to the router typing in 10.0.0.2 in a browser – jason – 2015-01-06T04:50:22.263

also, if it helps, running zenmap shows nothing in 'hosts' on the left side – jason – 2015-01-06T04:51:13.197

Belkin says if you power up with the reset button depressed for 15 seconds, the router forgets all config info and goes back to the factory state. Did you try that as well? – Fred – 2015-01-06T04:53:30.563

yes, i've tried belkin's methods, as well as others. belkin is a joke when it comes to tech support. – jason – 2015-01-06T04:55:02.983

UPDATE, 10.0.0.2 is now in the hosts panel on zenmap, but i think this is a remnant from when the computer used to be on the working network from the other router – jason – 2015-01-06T04:57:59.087

Start a fresh scan. Make sure the address isn't your scanning machine itself. If it isn't, then something is responding at that address. – Fred – 2015-01-06T05:04:41.050

Perhaps narrow the scan by a single port (like tcp 80) on all the private subnets. Other ports that may be open are udp 67, 68, tcp 443, 53 (tcp/udp)

nmap -p 80 -Pn -n -T5 10.0.0.0/8

It will scan quicker if you limit it to one or two ports. If it's bricked, you may need serial access to fix it.

Chev_603

Posted 2015-01-06T03:27:46.573

Reputation: 131

Actually, if you can connect to it whatsoever to run that scan, I would think you could simply run $ route or netstat -nr to see what your computer thinks the IP is, and also to check your routing tables for errors. Perhaps you accidentally configured an incorrect static route? In order to scan the network you'd need to somehow connect to it to begin with. If it's wireless and open you could also run wireshark and see from what IP the router is send arps to/from. – Chev_603 – 2015-03-28T00:53:20.047

If you reset the router, it should have DHCP service enabled. That means once you connected to it, you will get IP assigned. Then you can check the default gateway IP, that will be your router's IP (i.e. ipconfig /all when using Windows).

nochkin

Posted 2015-01-06T03:27:46.573

Reputation: 337

can't reset the router. have tried all types of hard resets, but it never resets, it's always in AP mode. – jason – 2015-01-06T04:26:01.267

Router does not provide any confirmation on reset. Just follow manufacturer's instructions on factory reset procedure, then try to connect again.

– nochkin – 2015-01-06T14:32:18.163

i've done all types of hard resets, including belkin's. and yes, the router does provide 'confirmation' on reset in a sense: it would allow me to access it at the default web interface. it doesn't, thus confirming it is not resetting. – jason – 2015-01-06T16:43:16.263

If it did not allow you to connect to the 100% known IP after you did the reset, that means your router is bricked. The factory default settings includes DHCP and default IP. But since you did not get IP assigned, then your router does not work properly (that's assuming you checked cables and simple things like that). – nochkin – 2015-01-06T16:47:58.343

If the router supports IPv6 you can find an IP address by pinging ff02::1. The exact command needed to ping that IP address depend on the OS you do it from, on Linux this command can be used ping6 -nc2 ff02::1%eth0.

If the router supports IPv4 you can find an IP address by scanning all the possible IP addresses. The 222 /8 prefixes it could possibly be using have in total 3724541952 IP addresses. If the connection between computer and router can run at 1Gbit/s, it can handle at least 83333 packets per second, at that speed you can scan all the IP addresses in less than 13 hours.

Some IP addresses are more likely than others. By trying the most likely IP addresses first, you'll probably find the correct one much faster. Ranges which makes sense to try first are private and link-local ranges 192.168.0.0/16, 172.16.0.0/12, 10.0.0.0/8, 100.64.0.0/10, 169.254.0.0/16.

For best performance you need to use a scanning tool, which only send one ARP request to each IP and look for an ARP reply.

If neither of those work, there should be some reset procedure, which will bring the router into a known configuration.

kasperd

Posted 2015-01-06T03:27:46.573

Reputation: 2 691