Cisco 870 and Dhcp

By Dumphrey ·
I have a cisco 870 router at my house. It does not like to get a dhcp address on its wan interface over my cable internet connection, and charter says they can't give me a static address as a home user. under the wan interface i have
ip address dhcp
this should work, and occasionaly it does. but if the house looses power, the router doesnt pick up a new address and i have to turn the interface off and ojn repetedly for anywhere from 30 min to an hour to get it to pick up an address. is their another command similar to ipconfig /release /renew i can use\/

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All Answers

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Cisco 871 and DHCP

by zac In reply to Cisco 870 and Dhcp

Did you get this to work? I have the 871 and can't seem to get DHCP to work on the WAN port either (I have RoadRunner.)

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I did eventually

by Dumphrey In reply to Cisco 871 and DHCP

Im trying to remember what I did. I had to start the router and let it boot up befor starting the cable modem. I also had to add the command "ip tcp adjust-mss 1452" undre the wan interface. This sets the packet fragmentaion amount apparently. Charter cable dhcp works now with that command and rebooting router first then plugging power into cable modem.. hope this helps.

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871 and cable modems

by john_45409 In reply to Cisco 870 and Dhcp

Try a hard reboot of your cable modem.

set a default route to-

ip route dhcp

and your wan IP to-

ip address dhcp

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route won't help need to NAT

by bhanshali In reply to 871 and cable modems

You will need to NAT inside add to wan interface:

to get ip add from wan do following:

config t
int f4
ip add dhcp
no shut

then restart cable modem and router should get the ip add, also type following command to see if you getting ip add:

sh int f4 <<<and on top see what is the ip add.

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by zilbel1038 In reply to 871 and cable modems

Thank you for this! I finally got my 871 working!!!!

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