[afnog] Cisco 1605-R Router problem !

Brian Candler B.Candler at pobox.com
Fri Oct 22 10:39:27 EAT 2004

On Fri, Oct 22, 2004 at 12:08:24PM +0200, Alamicha Chapuma wrote:
> | > The sites which loose connectivity are the Breezcom ones.  They are on a
> | > 172.16.1.x   network while the others are on a 172.30.x.x network.
> |
> | Does that mean you are overlaying two IP ranges on the same physical
> network
> | (the Cisco has 'ip address' and 'ip address
> | secondary')?
> No.  The cisco has an ip of and mask so it can talk
> to a wide range of hosts.

OK, then that's a single "flat" (unrouted) network.

> However, the standard configuration we have is
> that the client sites are set with the SUs on a 172.16.1.x   ip address.
> The 172.30.x.x  sites go through an access point which acts as a router and
> has an interface set to

Hmm, a problem is starting to become apparent. But we'll need a diagram, and
perhaps some configs, to make this clearer. From what you'd said so far:

                             .\|/ wireless client
                           .   | 172.30.y.y
                         .     | Netmask??
                       .      RTR
                     .         | 172.z.z.z
                   .           | Netmask??
                 .             +------------+---
               .                            | 172.q.q.q
             .                              | Netmask??
           .                               PC
       | 172.x.x.x
       | Netmask??
       | Netmask??
                 ethernet                 |
                                          | mask
                                          | z.z.z.z/z
                                      ethernet backbone

Sorry I don't know what "SU" stands for, but you've said it's a router. So
I'm going to guess you have a static route on your Cisco to direct traffic
for via it:

    ip route

Or else you are doing proxy ARP trickery on the SU.

If the SU is a router, that also means it has two separate IP addresses and
netmasks, one for the ethernet side, one for the wireless side. Is that

If so, then it looks like you have a design problem which would certainly
cause ARP problems. But before I comment further, perhaps you could make any
corrections needed to the diagram above.

"RTR" is the "router or routing server" which you mentioned in your mail.
Perhaps you can explain what that is and how it is configured.

It would also be useful to see the interface configs (ip addresses and
netmasks) and static routes on the Cisco and on the SU.

You mentioned other wireless access points sitting on the same ethernet
segment, so maybe they should be included in the diagram too. Are they
routers, or bridges?



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