Link to home
Start Free TrialLog in
Avatar of rajeev7086
rajeev7086

asked on

multiple cable modem sharing

I have 4 cox high speed internet connection delivered with speed (15Mb down and 2mb up ) thru cable modem .

Each cable modem is allocated a ip address like :- 68.68.128.130/25 ,, gateway - 68.68.128.129

other three ip address are 68.68.128.145, 68.68.128.185 , 68.68.128.164

now i want to use them on single device like cisco router with 5 ethernet ports and share them with NAT to my users connected to ethernet 5 using dhcp and share it equally .

issue is - all connection have same gateway and are part of single subnet .

I tried various devices like mikrotik rb 450 , still there is no way out to configure same subnet on different ether ports .

Avatar of meverest
meverest
Flag of Australia image

Hi,

you can do this with Mikrotik for sure - I do it all the time.

the easiest way is to enable nat on every modem, then use the local address of the modem for each gateway for the router routes.

>> Each cable modem is allocated a ip address like :- 68.68.128.130/25 ,, gateway - 68.68.128.129

why do they all have /25 address?

also, although the isp has given all the same default gateway, they /can/ give you multiple gateway, so you should ask them.  Maybe they /won't/ do it, but they certainly /can/ do it!  If they will help you out like that, then it will make your job a whole lot easier.

Otherwise, you can try something like mikrotik rb490 which has 9 ethernet ports.  mikrotik routerOS v3+ supports routing by interface as well as gateway, so then you just plug each modem into individual ethernet ports and balance your outbound routes by interface instead of gateway.

Cheers!
Avatar of rajeev7086
rajeev7086

ASKER

ISP is not able to provide multiple gateway for each connection .
There is now way we can configure internal ip on modem since we do not have access to modem .
I tried with mikrotik with interface as gateway , it does not work .
 
can u please eloborate on this how to do that .
 
 
 
 
http://forum.mikrotik.com/viewtopic.php?f=3&t=27905
please refer this link , this is the exact problem that i face . This has all the details where we are stuck and what exact problem is .
please sugest the config details , i can simulate the same .
 
ASKER CERTIFIED SOLUTION
Avatar of meverest
meverest
Flag of Australia image

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
testing with the latest version only !
please support the config details as per the forum i added . that will be much helpfull
 
 
i have done the config with interface based routing . it works but it keeps arp for each and every external ip visited thru the router .
ARP entries are getting added and alos router is experiencing lot of load due to so many arp entries in the table .
do u have some idea about it ?
 
 
Hi,

yes - I have generally got best results by 'encouraging' the ISP to provide additional gateway addresses.  It's really not so hard for them to do it if you think about it (all they have to do is put more ip addresses on their border router interface.

Most ISPs are happy to help, but the very large isps who have their own massive beauracracy to work through are usually near impossible to get through to the right person.

Cheers.
ISP is large and do not agree for seperate subnet and gateway .
do u have some idea of how many arp entries can router os support .
will this setup work with 200 pc attached . i ll be using higher grade Pc for mikrotik with multiple lan cards .
i m not able to understand what issues will be there due to so many arp entries added to mikrotik for each and ever site visited . this will surely not work in case there is some flooding due to some virus and stuff.
 
 
 
>> ISP is large and do not agree for seperate subnet and gateway .

that is a shame (unfortunately typical of the big ones)

>> do u have some idea of how many arp entries can router os support .

they do not take a great deal of memory, and not much CPU overhead.  I would expect it to work ok, keep an eye on the system/resorces and make sure that cpu stays within reasonable range i.e mostly less than 90% and that there is sufficient available ram.

If it starts to struggle, consider hardware upgrade.

Cheers!