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Community Member

Cisco 819 Router configuration for Comcast residential


I am having an odd problem with my residential Comcast connection via a Cisco 819 router.

I seem to be able to connect to the Comcast IPv6 network just fine with the interface configuration of my router, but I cannot get a DHCP IPv4 address assigned to the interface of my 819 router.

Of course, you would ask what has changed? 

All I did was request Comcast change my speed from their performance tier (12 MBPs down/2 MBPs up) to the blast tier (50 MBPs down/10 MBPs up)


Here is the configuration of the Comcast facing interface on my 819:

interface GigabitEthernet0
 description WAN Interface to Comcast
 ip address dhcp
 ip access-group BLOCK-TELNET in
 no ip unreachables
 no ip proxy-arp
 ip nat outside
 ip virtual-reassembly in
 zone-member security OUTSIDE
 duplex auto
 speed auto
 ipv6 address dhcp
 ipv6 enable
 ipv6 dhcp client pd hint ::/60
 ipv6 dhcp client pd comcast-ipv6
 no cdp enable

IPv6 DHCP works fine.  IPv4 DHCP does not.  Are they any IPv4 configuration parameters missing?

Thank for your help.


Everyone's tags (3)
Community Member

i was going to suggest that

i was going to suggest that maybe you were missing a permit statement on your inbound access list that would allow DHCP traffic in, but i see that its receiving for IPv6

Community Member

Community,After browsing more


After browsing more I found the solution in another community post from 2010:


VIP Purple



I am facing a problem where I can get an IPv6 address just fine with the configuration you posted, but only on the WAN interface. The LAN interface just keeps getting a link local. Would you mind posting the config of your LAN interface ?

Thanks a bunch in advance...

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