DHCP on 871 WAN Port

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Nov 12th, 2009
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I'm having some issues with configuring DHCP on the WAN port (Fa4) on a Cisco 871W. Basically, I want to configure this unit locally, so I can ship it to an existing broadband user to just plug in to their Broadband modem and hey presto, it will work!!!

I've configured the WAN port for DHCP, and had some minor success getting an IP and default route etc for the next hop to the existing DSL router, but now I'm getting no IP address assigned, whatever I try.

The DSL router is a Netgear and it's happily chugging out IP's to other DHCP clients...

Am I doing something really, really stupid?!

Thanks in advance

Campbell Thompson

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paolo bevilacqua Fri, 11/13/2009 - 07:13
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Sometime IOS DHCP client just don't work.

Try upgrading IOS.

campbell.thomps... Fri, 11/13/2009 - 07:51
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I'm up to the latest IOS on this router.

I've managed to make some progress... I think...

I removed the:

zone-member security out-zone

from the fastethernet4 config and can then get DHCP traffic...

So, leads me to the question, can I leave that on and add an exception to all DHCP traffic to the zone?

paolo bevilacqua Fri, 11/13/2009 - 08:01
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To be honest, I think you can do without ZBFW in 99.9% of the cases.

rchambers Wed, 05/19/2010 - 05:49
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I have an even more esoteric problem with the 871 WAN port.

I have an 871W that I use at various locations (hotels, golf clubs, meeting centers) to provide a "company network" hotspot for various offsite meetings that the executives of the company host.

I'm running a pretty recent IOS on it c870-advipservicesk9-mz.124-15.T13

Here's my issue:

With the FA 4 configured with

IP address DHCP sales3    (hostname of the box so it is viewable in the host dhcp server)

Anyway, most sites we go to are served by Linksys (aka Cisco home) devices.  I have a couple at the office to test with.

So my problem is this:

At some sites the 871 will not be able to get a DHCP address from the host router where laptops and such can get addresses.

We tried it out in the office and one Linksys had no problems giving out addresses and a newer one did not.

We sniffed the connection to the new linksys and see that the 871W is doing the DHCP DISCOVER broadcast which we trap at the port on the linksys but the linksys does not respond with an offer.

Has anyone else seen this happen?  On the old linksys the handshake goes as you'd expect and the 871 gets an address and brings up the tunnel.




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