Few minutes internet works!

[swaminathan]

Hi

In one setup, we have fibre optic connection given by the ISP upto Distribution box inside the house where the fibre optic cable is connected to HUAWEI-ECHOLFIE HG865 terminal .From the RJ 45 port in that device , the ethernet cable goes to the DLINK 8 port switch. All the 8 ports are connected with ethernet cables to 8 rooms going concealed through the wall.
Our ISP person tested the connection by connecting one patch cable (from the DLINK SWITCH via the wall socket)to the WAN port of LINKSYS WRT300N wireless router and connecting other ethernet cable from the lan port of the router to the laptop ,setup the username ,password, encapsulation pppoe and configured the internet .found working.
I tried to configure the wireless in the house by fixing LINKSYS access point in some rooms.Here the problem started.
I cannot fix the LINKSYS router inside the DB in front portion of the house since there is no space in that and cannot keep the linksys router outside also, So I kept the linksys router inside one room and tried by connecting cable from the wall socket to a 5 ports mini switch and from the mini switch I connected one cable to WAN PORT of the linksys router and one cable to linksys's lan port because I want to share the internet in all the rooms.
I checked the internet in all the rooms by taking one laptop to all the rooms and checked through the access point configured in each room.
After few minutes internet drops and the led's in the LINSKYS router starts continuously blinks as if there is some problem

I know that it should not be connected in this way but my question is why internet works sometimes and starts disconnection.


Thanks & Regards
S.Swaminathan

N.B: Currently the setup is working with ADSL LINE directly connected to WAN PORT of LINKSYS ROUTER and connecting the LAN PORT of LINKSYS to DLINK SWITCH without any problem!
I need to know the reason why internet disconnects in the first mentioned connection explained in cisco terms Please!

[bs_kwaj]

Without understanding all the details, it sounds like you connected a switch to a switch. If you don't have something in place to prevent loops, then eventually loops will occur, or so I think.
I assume then that you're good to go until an uncontrolled loop happens and your switches lose their minds.

Now we wait for smart people, like BE, to show up and get more specific. ;)


(Uncontrolled loop! Sounds like an oxymoron, eh?)

[swaminathan]

Without understanding all the details, it sounds like you connected a switch to a switch. If you don't have something in place to prevent loops, then eventually loops will occur, or so I think.
I assume then that you're good to go until an uncontrolled loop happens and your switches lose their minds.

Now we wait for smart people, like BE, to show up and get more specific. ;)


(Uncontrolled loop! Sounds like an oxymoron, eh?)

Hi

Thank you for your reply and I saw this "multiple connections between two network switches or two ports on the same switch connected to each other"

at http://en.wikipedia.org/wiki/Switching_loop

I suppose that there is no layer 2 looping in my issue.

As you said, let us wait for the seniors input for the clear explanations.

[omd]

I read and reread your description until I felt that I understood your setup. I formulated in my mind how I would suggest you rewire things. Then I read the edit to your post and saw that you had already rewired in the manner that I was going to suggest.

Your question stated that you wanted to understand why the first setup worked for a while and then quit. Unfortunately, it can often be very difficult to understand why something does _not_ work, so I think that I would concentrate on understanding why your current setup is a better design than the original setup.

I would draw out both designs on paper. Then consider what happens to a broadcast frame originating from a client connected wirelessly to the Linksys router. These frames should only be seen by devices connected to the LAN port of the router, but in you first setup, they will be seen by the WAN port also, as well as, really, your entire network, including the DSL modem. The first setup also creates two layer 3 networks, one for the LAN side and one for the WAN side of the router. Then, you have these tied together at layer 2 through the 5 port switch. (By the way, in the drawing I made, I actually did not see any loops at all, much less a loop that might not be caught by spanning tree.)

In your second setup, broadcast frames will only be seen by the devices that really need to seem them, making for a cleaner design with no traffic going places it doesn't need to.

The following is my best guess as to why the first setup seems to work for a while and then quits.

The Linksys router is running a dhcp client on its WAN interface. This is used to obtain an IP address from your ISP on your ISP's logical network. It is also running a dhcp server on its LAN interface to provide IP addresses, to your home's devices, on its LAN's logical network; often 192.168.0.0/24. I'm guessing that when the router starts up, the WAN interface gets an IP address from you ISP and things work fine for a while. But when it comes time to renew the lease, because the router's LAN and WAN interfaces are tied together at layer 2, the router's WAN interface gets a new IP address from its own dhcp server. At this point, the router no longer has the ISP as its way out to the Internet and things stop working.

As I said, this is only a guess. I did not take time to read the specifics of how a dhcp lease renewal works.

I hope that helps.

[swaminathan]

I read and reread your description until I felt that I understood your setup. I formulated in my mind how I would suggest you rewire things. Then I read the edit to your post and saw that you had already rewired in the manner that I was going to suggest.

Your question stated that you wanted to understand why the first setup worked for a while and then quit. Unfortunately, it can often be very difficult to understand why something does _not_ work, so I think that I would concentrate on understanding why your current setup is a better design than the original setup.

I would draw out both designs on paper. Then consider what happens to a broadcast frame originating from a client connected wirelessly to the Linksys router. These frames should only be seen by devices connected to the LAN port of the router, but in you first setup, they will be seen by the WAN port also, as well as, really, your entire network, including the DSL modem. The first setup also creates two layer 3 networks, one for the LAN side and one for the WAN side of the router. Then, you have these tied together at layer 2 through the 5 port switch. (By the way, in the drawing I made, I actually did not see any loops at all, much less a loop that might not be caught by spanning tree.)

In your second setup, broadcast frames will only be seen by the devices that really need to seem them, making for a cleaner design with no traffic going places it doesn't need to.

The following is my best guess as to why the first setup seems to work for a while and then quits.

The Linksys router is running a dhcp client on its WAN interface. This is used to obtain an IP address from your ISP on your ISP's logical network. It is also running a dhcp server on its LAN interface to provide IP addresses, to your home's devices, on its LAN's logical network; often 192.168.0.0/24. I'm guessing that when the router starts up, the WAN interface gets an IP address from you ISP and things work fine for a while. But when it comes time to renew the lease, because the router's LAN and WAN interfaces are tied together at layer 2, the router's WAN interface gets a new IP address from its own dhcp server. At this point, the router no longer has the ISP as its way out to the Internet and things stop working.

As I said, this is only a guess. I did not take time to read the specifics of how a dhcp lease renewal works.

I hope that helps.


Hi

Thank you for your reply and I think your assumptions are almost correct regarding the DHCP concept and regarding the abnormal blinking of the led's what do you think?

[swaminathan]

Hi

Thank you for your reply and I think your assumptions are almost correct regarding the DHCP concept and regarding the abnormal blinking of the led's what do you think?

Hi

I am in the preparation of CCNA ; that is why I posted this issue in the forum where prestigious experienced senior members presenting their invaluable contributions ; which help lot of aspirants in their road of CCNA JOURNEY!

[Big Evil]

https://learningnetwork.cisco.com/message/213478#213478