I have a Cisco 871W, and I need help correctly creating an ACL that will allow for the public-facing interface (fa4) to receive an IP from my ISP.
With no ACL, I get an IP address with no issue. With an ACL that actually does something (allowing some web and TS traffic), I will not get a DHCP address (the implicit deny at the end).
I have tried permitting all traffic from the DHCP server (it uses a private IP of 172.19.97.40), but still no DHCP. I tried permitting all traffic from any source to ports 546 and 547, but again with no success.
I can end my ACL with a permit all UDP, and I get an IP address via DHCP, but of course I don't want to allow this.
My guess is that the second part of the DHCP process, where the DHCP server sends the client an IP address but still using the broadcast address, it where the problem is. I am not sure how to work around this.
Thanks for your help.