eriji
Premium
join:2002-05-23
Orangeburg, SC
| [Windows] Can I access cable modem menu through router?
Hopefully a simple problem:
Would like to access the menus on my Ambit U10C020 modem from the computer(s) when they are connected to the router.
ISP: Charter Type: HSI Cable Internet Always On.
Setup: CableNetwork ---> Ambit-Cable-Modem ---> Linksys-BEFSR41-Router ----> Computer(s).
BEFSR41 is 192.168.100.100, computers are 192.168.100.101-xxx.
Ambit modem is 192.168.100.1 (and cannot be changed.)
Subnet masks are 255.255.255.0 everywhere.
Computers are mostly manually configured IP due to routing of external services on specific ports to specific computers (PC-Anywhere, Remote-Access, DB Access, FTP, etc.)
Some computers come and go and are DHCP (laptops, guests, repair, etc.)
When I try to access the modem(192.168.100.1) through router from any computer (e.g. 192.168.100.105), then it cannot reach modem. i.e. cannot ping modem and cannot connect to modem menu interface with browser.
I CAN access the modem menus at 192.168.100.1 when directly connected (computer-CAT5->modem) (but that doesn't work for external network access because of different MAC on PC and router.)
How can I (or is it possible to) configure so that I can reach the modem?
I can access menus on the router, I can access the other computers, just not the modem.
Before I upgraded to 10M I had a Motorola Surfboard, and I could access the menus through the router (but only if the connection was online and working...didn't help for outages.)
Charter says to ask Linksys. Linksys says to ask Charter, but if I insist, they babble incoherently or reference documents that have nothing to do with the solution.
If you ask why, I will be forced to describe some of the horror stories talking to Charter Customer Service, and that is not the question.
Thanks for any help!
--eric |
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JTY
join:2004-05-29
Ellensburg, WA | Change your router to a different subnet, and it should work. |
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eriji
Premium
join:2002-05-23
Orangeburg, SC
| I tried changing the router to 192.168.2.1 at one point, and then could not access the router or the outside network.
I had to change the computer(s) IP to 192.168.2.10x for it to work. I tried changing the subnet mask on computer first to 255.255.0.0 which did not work. (I had changed the router at the same time I changed it to . .2.1.
Now I've never been real comfortable with subnet masks, so I may be missing something, but I understood that the . .0.0 change would work. But it really doesn't.
thanks |
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muiredised
ESSE QUAM VIDERI
join:2007-06-11
Tacoma, WA
| reply to eriji
I solved this same problem by adding a static route on my gateway to the network my modem is using. My IP scheme is different from yours but here goes.
Cable modem -- 192.168.100.1
Gateway router -- 192.168.0.1
LAN computers -- 192.168.0.x
Under the "advanced routing" interface of my router I added a static route. The info for the route is that of the target network.
Destination LAN IP -- 192.168.100.1
Subnet mask -- 255.255.255.0
Gateway -- 192.168.100.1
Hop count -- 1
Interface -- Internet
Then I can type in 192.168.100.1 from my computer which has an IP address like 192.168.0.20 and I access my modem's interface with no problems.
--
Assiduus usus uni rei deditus et ingenium et artem saepe vincit |
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eriji
Premium
join:2002-05-23
Orangeburg, SC
| Thanks for the info. It didn't work first time around, but a light is beginning to dawn (and I looked at the router routing table) and I have some ideas I will try tonight.
The Linksys rep kept saying that my modem and router had the same IP address, which is incorrect, but they are on the same subnet.
Thanks again, I'll post the results later. |
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muiredised
ESSE QUAM VIDERI
join:2007-06-11
Tacoma, WA
1 edit | Change your LAN IP scheme so that your LAN and your modem are on different subnets and adding a static route will work.
Your network (if i understand it correctly) looks something like this:
ISP NETWORK -------|
| |
WAN--> ------------ |B
| MODEM | |R
LAN--> ------------ |I
192.168.100.1 |D
| |G
| |E
| |D
xxx.xxx.xxx.xxx -----|
WAN--> ------------
| ROUTER |
LAN--> ------------
192.168.100.2
| |
| |
| |
192.168.100.50 192.168.100.51
---------- ----------
| PC #1 | | PC #2 |
---------- ----------
Because your ROUTER is designed to segregate networks, it is not going to pass packets from its LAN side to its WAN side if those packets are destined for a LAN address. If you try to add a static route like I suggested, it will not work because your ROUTER believes that LAN packets need to stay on the LAN side and gets confuzzled that you want to pass them somewhere else. Improper routing.
If instead you change your network IP scheme to have something like this:
ISP NETWORK -------|
| |
WAN--> ------------ |B
| MODEM | |R
LAN--> ------------ |I
192.168.100.1 |D
| |G
| |E
| |D
xxx.xxx.xxx.xxx -----|
WAN--> ------------
| ROUTER |<---- static route from
LAN--> ------------ LAN to 192.168.100.1
192.168.0.1
| |
| |
| |
192.168.0.50 192.168.0.51
---------- ----------
| PC #1 | | PC #2 |
---------- ----------
Your ROUTER now understands that any packets destined for 192.168.100.x need to get routed to 192.168.100.1 so it passes the request on through to the WAN interface, the request hits the MODEM and the MODEM resolves the request.
--
Assiduus usus uni rei deditus et ingenium et artem saepe vincit |
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eriji
Premium
join:2002-05-23
Orangeburg, SC
| Thank you so much for the WONDERFUL diagram and great explanation. I more than appreciate the time you took to answer.
I apologize it took me so long to respond, I got swamped at work and haven't had a breather until last night and this morning.
I think I figured out where my understanding was lacking, and I'm pretty sure I can get it working now.
Thanks again so much!!!!!! |
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bichenoubi
join:2008-08-15
| Hi, I'm looking to do the same thing.
But me the modem has ip 10.0.0.138 and router has ip 192.168.1.1 with clients like 192.168.1.1xx
Under the "advanced routing" on my linksys wrt54g router I entered:
Select set number: 1()
Enter Route Name: Modem
Destination LAN IP -- 10.0.0.138
Subnet mask -- 255.255.255.0
Gateway -- 10.0.0.138
Interface -- Wan(Internet)
So it's like muiredised said earlier but changed 192.168.100.1 to 10.0.0.138.
But it doesn't work. I get this error message on the router after I click save settings : "Gateway not directly reachable through that interface"
What should I do then ?
Thank you |
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muiredised
ESSE QUAM VIDERI
join:2007-06-11
Tacoma, WA
2 edits | Your modem management interface has an IP of 10.0.0.138 which suggests that perhaps your subnet mask should be 255.0.0.0
I have never come across a modem using that IP addy for its management interface so out of curiosity, what model of modem do you have?
--
Assiduus usus uni rei deditus et ingenium et artem saepe vincit |
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OZO
Premium
join:2003-01-17
| reply to eriji
The problem with that scenario is - in order for the router to communicate with modem - the modem should be on the same subnet as router's WAN interface. If it's not - you're out of the luck.
In other words, if modem has hardcoded IP 192.168.100.1 your WAN interface should be on the 192.168.100.XXX subnet. But the problem here is that subnet is not yours, it usually was given to you by your ISP and you can't change it. As well as you can not use any other IP on that subnet except given to you by contract (it simply may be used by other subscribers).
Communication with modem which is outside of LAN (connecting to WAN side of the router) is possible only if IPS gives you additional IP (usually a static IP) and you can assign that IP to your modem. Let me know if it's the case (you do have an additional IP) and I (or any other forum member) may help you with setup.
--
Keep it simple, it'll become complex by itself... |
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muiredised
ESSE QUAM VIDERI
join:2007-06-11
Tacoma, WA
| said by OZO  :Communication with modem which is outside of LAN (connecting to WAN side of the router) is possible only if IPS gives you additional IP (usually a static IP) Not correct. I use this very setup at 3 locations with no problems whatsoever.
--
Assiduus usus uni rei deditus et ingenium et artem saepe vincit |
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OZO
Premium
join:2003-01-17
| It is. Unless:
1) your router has ability to support several WAN interfaces (it's quite expensive) and you assign a separate WAN interface for subnet dedicated to connection with modem. Most cheap routers do not have it.
2) you assign and use IP that belongs to ISP and it's waiting for a time to be discovered/broken.
Pick your case...
Again, in order to communicate with modem - router's WAN interface must be on the same subnet with that modem.
--
Keep it simple, it'll become complex by itself... |
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tubbynet
reminds me of the danse russe
Premium
join:2008-01-16
Chandler, AZ
 ·Cox HSI
 ·Callcentric
 ·Sprint Mobile Broa..
 ·FrontierNet Intern..
1 edit | wrong again. logically, your argument makes sense. however, you are assuming a static-type of routing...
when dealing wtih a "router" you have to realize that if the device can "sense" the existance of another device (or is TOLD that device exists), and it can discover how to get there (or is told), then it will work just fine.
you have to understand that much of what is being done to DSL/cable modems is transparent on the back end to the user. i can pull up logs in my sb5120 cable modem that shows that i am assigned several different ip addresses (one public, one private) and that my gateways are assigned to RFC1918 addresses.
your typical router knows about its subnet on the LAN side, and then it knows that all other traffic is sent out the "WAN" interface. when you put in 192.168.100.1 into your address bar, your router realizes that it doesn't have a route to the device, so it forwards this request out the WAN link. the modem then picks up the packet and replies back out the interface the request came in on. neither device really knows the full story of the other, but the communication just "works".
tubby2811#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 68.xxx.xxx.x to network 0.0.0.0
68.0.0.0/20 is subnetted, 1 subnets
C 68.xxx.xxx.0 is directly connected, FastEthernet0/0
172.19.0.0/32 is subnetted, 1 subnets
S 172.19.73.37 [254/0] via 68.xxx.xxx.x, FastEthernet0/0
C 192.168.189.0/24 is directly connected, FastEthernet0/1
S* 0.0.0.0/0 [254/0] via 68.xxx.xxx.x
that is the routing table off my gateway cisco 2811 router. no dynamic routing, no bgp, no static routes, just what i pull from DHCP from Cox. doesn't know of the 192.168.100.0 subnet, but i can still hit it, as shown
C:\Documents and Settings\SnyderQ>ping 192.168.100.1
Pinging 192.168.100.1 with 32 bytes of data:
Reply from 192.168.100.1: bytes=32 time=3ms TTL=63
Reply from 192.168.100.1: bytes=32 time=2ms TTL=63
Reply from 192.168.100.1: bytes=32 time=3ms TTL=63
Reply from 192.168.100.1: bytes=32 time=2ms TTL=63
Ping statistics for 192.168.100.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 3ms, Average = 2ms
it just works!
q. |
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OZO
Premium
join:2003-01-17
| said by tubbynet :your typical router knows about its subnet on the LAN side, and then it knows that all other traffic is sent out the "WAN" interface. when you put in 192.168.100.1 into your address bar, your router realizes that it doesn't have a route to the device, so it forwards this request out the WAN link. the modem then picks up the packet and replies back out the interface the request came in on. neither device really knows the full story of the other, but the communication just "works". The problem is - if a packet goes through WAN interface, it EITHER goes to an IP that is within specified WAN subnet (if your modem is on the same subnet, and, as I've said, it works) OR (the most common case) it goes to ISP provided gateway (and that what will exactly happen in all other cases). There is no other ways for "just works".
If your WAN side of the router doesn't have a second interface (that shares subnet with modem) you even should not be able to assign a static route (it confuses the router). And that's exactly what bichenoubi has noticed:
said by tubbynet :But it doesn't work. I get this error message on the router after I click save settings : "Gateway not directly reachable through that interface" Check your cisco 2811 router for the second interface, if it works.
--
Keep it simple, it'll become complex by itself... |
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muiredised
ESSE QUAM VIDERI
join:2007-06-11
Tacoma, WA
| Sparing the technical details...
The modem can be thought of as a highly specialized router with a media converter on its WAN port. This router bridges its WAN IP to a single LAN device. In some products it also creates its own LAN subnet in order to host an administrative UI. Internally the modem has two virtual interfaces... the one that is bridged to the ISP network and the one that it uses internally to host the admin UI. Each of these interfaces has its own MAC address. When you add a static route to the WAN side of a router that uses ethernet on the WAN side it tries to resolve this route by using ARP. If set up properly the internal interface of the modem will respond to this ARP request and packets will get routed properly to it.
--
Assiduus usus uni rei deditus et ingenium et artem saepe vincit |
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bichenoubi
join:2008-08-15
| reply to muiredised
Modem: Thomson SpeedTouch 510 (ip: 10.0.0.138) in briged mode without dhcp server.
Router: Linksys wrt54g (ip: 192.168.1.1) doing a ppoe connection to the modem and having a dhcp server enabled (clients ip: 192.168.1.100 to 192.168.1.254).
with this, what should I enter in that page: 
(took the screen from internet, this is not an actual screenshot from me) |
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muiredised
ESSE QUAM VIDERI
join:2007-06-11
Tacoma, WA
| Have you tried this....
Route name -> modem
Destination LAN IP -> 10.0.0.0
Subnet Mask -> 255.0.0.0
Default Gateway -> 10.0.0.138
Interface -> Internet
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Assiduus usus uni rei deditus et ingenium et artem saepe vincit |
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