[PLUG] How to detect ppp address change remotely?

[Rich Burroughs]

Tom,

I'm a little confused. I'm not a routing guru by any means though :)

But there's a NIC in the gateway router? Why aren't the downstream routers
using that as their default gateway? And then it would handle the routing
to Verizon?

Rich

On Saturday, March 17, 2012, Tom Sharples <tsharples at qorvus.com> wrote:
> Hello all,
>
> We have several installations of embedded wireless routers (running
> slack on a 2.4 kernel) in which the gateway router_1 uses a Verizon 3G
> USB modem (ppp0) as its connection to the outside world, and one or more
> downstream router_2 have 5.8Ghz wireless links to router_1, and thus
> route traffic to the outside world through the same ppp0 3G connection.
>
> Verizon has a habit of constantly changing the ppp0 IP address often
> sometime several time per hour. I would like to figure out a way that
> the downstream router_2 can be made aware of that ppp0 address change at
> router_1 within a minute or two of it happening. The obvious way seemed
> to be running a cronjob traceroute from the router_2 to a known outside
> IP, with a limit of two of three hops, and grepping the first public IP
> and looking for the change. However, for some reason that shows the
> Verizon gateway router on their tower as the first public IP rather that
> the locally assigned ppp0 public IP address. Any suggestions for how to
> determine that ppp0 IP using standard tools and pref. without writing
> e.g. inter-router communications scripts etc. would be welcome.
>
>
verizon_tower------------------[3G_modem(ppp0)]-[router_1]---------------[5.8Ghz_link]----------------[router_2]
>
> Thanks,
>
> Tom S.
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