[afnog] Router Interface not responding

[Brian Candler]

On Wed, Jun 09, 2004 at 09:50:33AM +0200, Alamicha Chapuma wrote:
> We have a router with 2 ethernet Interfaces.  One is connected to a LAN of
> real ips 62.x.x.x and the other to a wireless network with private ips
> 172.x.x.x
> 
> All has been working fine until recently where we are failing to ping the
> wireless interface of the router from the LAN side of it. Also some of the
> wireless devices on the wireless side of this router could not be pinged.
> The only thing that happened is we reconfigured a wireless access point to
> work in router mode.

The "only" thing is very significant by the sounds of it. Tell me if these
diagrams are correct:

BEFORE:

      62.x.x.x      172.x.x.x
  ------------ R ---------------
     Ethernet        Wireless

AFTER:

      62.x.x.x   172.x.x.x      172.y.y.y
  ------------ R ---------- AP ------------
     Ethernet1    Ethernet2     Wireless

If the access point is a router, then you now have three subnets instead of
two. That means that
(1) Ethernet2 and Wireless need separate prefixes which don't overlap
(2) Router R needs a static route to 172.y.y.y via the AP's IP address on
    Ethernet2

Wireless users will point default route at the AP's IP address on wireless,
and the AP needs to point default route at R's address on Ethernet2.

Notice that R can no longer directly reach wireless machines, nor ARP for
them, because 'Ethernet2' and 'Wireless' are two separate broadcast domains.

> This wireless access point can be reached from the
> 62.x.x.x LAN.

Yes, because its IP address is on Ethernet2.

> Further the router can be pinged from the wireless side (i.e.
> a host on the wireless network with ip 172.x.x.x can ping the router's
> 172.x.x.x address).

The AP is directly connected to both subnets.

> How do we resolve this problem?  A traceroute from our 62.x.x.x network gets
> up to the router and stalls/timesout on the router.  However, if we ping the
> 172.x.x.x  interface from the router itself there is no problem.
> 
> For information purposes the router is set as the main gateway on the
> wireless network.

That doesn't really mean much to me, unless you mean "the AP points its
default route at R"

> What to do????

If you've reconfigured your network into three separate broadcast domains as
shown above, then each device needs routes to find the other networks.

Regards,

Brian.