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Riptawr

Member

Registered: 2011-09-14

Posts: 18

Checking secondary internet connection with only one NIC - Possible?

Hey all,

I am currently stuck at the task of utilizing a secondary internet connection from a different provider. The picture is as follows(stripped details for convenience):
1.) Simple gateway server-cluster with no slots for further NICs
2.) "Main" internet connection (provider A) with static IP over eth0
3.) "Reserve" internet connection (provider B) with dynamic IP
4.) a simple script that pings eth0 and then google to find out if the link is up

Now there are two problems:
A.) how do i know Reserve is working while Main is connected, while having only eth0 to check it?
B.) how do i know when it is the other way round, so i should switch the profiles back to Main?

My idea was to create an interface alias with netcfg that would up eth0 and postup its alias eth0:1 with configurations for both providers respectively and telling a script to switch in between them, although the router(i placed there temporary) doesn't seem to recognize the alias in its ARP tables als separate entry. It is also only pingable on the host, not from the router - that is why i'm using static ip on both for testing.
Reserve netcfg profile uses the router as gateway / dns - and gives a gateway failed message. If i use eth0 as gateway i get "net.ipv6.conf.eth0:1.accept_ra" is an unknown key.

I thought about using the first connection to ping provider B's gateway/dns servers, but that wouldn't necessary mean the link is up in between us, nor exclude any internal network issues the provider may have.
Exchanging the gateway-cluster for a dual-link router would be the last option, due to their use as openVPN and DNS servers (the amount of clients with unique VPN keys is too big for me to spend the rest of my summer re-generating them on a cisco router)

Thanks in advance,
Rip

fukawi2

Ex-Administratorino

From: .vic.au

Registered: 2007-09-28

Posts: 6,226

Website

Re: Checking secondary internet connection with only one NIC - Possible?

This script might help you...
https://github.com/fukawi2/pb-route
(yes, shameless self promotion, but I wrote it with pretty much exactly the intent you are talking about)

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Riptawr

Member

Registered: 2011-09-14

Posts: 18

Re: Checking secondary internet connection with only one NIC - Possible?

Thanks, i'll try it out.