trying to get a Cisco 2811 to work with a cable modem.

[trunolimit]

I have 2811 router. the WAN side is connected to a DSL modem on FE0/1 and the IP address is set to a static IP. What I want to do is take out that DSL and put in a cable modem. Now, theoretically I can just attach the cable modem to FE0/1 in place of the DSL. Unfortunately this doesn't work. I do a show ip int brief and the interface is up and up but none of the computers on the network can get online. I tried to switch FE0/1 to DHCP and FE0/1 won't grab an address from the cable modem. doing a show ip int brief shows the interface up and up but the ip is unassigned. WHY WONT IT WORK???????

I did a test on the cable modem. I plugged my laptop directly into the modem, I got a 66.XX.XX.XX address and i was able to surf the web just fine. here is the router config

logging message-counter syslog
logging buffered 560000
enable secret 5 ***************
!
aaa new-model
!
!
aaa authentication login VPNauthen local
aaa authorization network groupauthor local
!
!
aaa session-id common
clock timezone EST -5
clock summer-time EDT recurring
!
dot11 syslog
no ip source-route
!
!
ip cef
!
!
no ip domain lookup
ip multicast-routing
ip inspect log drop-pkt
ip inspect max-incomplete low 400
ip inspect max-incomplete high 500
ip inspect one-minute low 300
ip inspect one-minute high 400
ip inspect udp idle-time 300
ip inspect dns-timeout 10
ip inspect tcp idle-time 300
ip inspect tcp synwait-time 10
ip inspect tcp max-incomplete host 50 block-time 0
ip inspect name inspect_rule ftp
ip inspect name inspect_rule dns
ip inspect name inspect_rule http
ip inspect name inspect_rule https
ip inspect name inspect_rule icmp
ip inspect name inspect_rule imap
ip inspect name inspect_rule smtp
ip inspect name inspect_rule ntp
ip inspect name inspect_rule tcp
ip inspect name inspect_rule udp
ip inspect name inspect_rule pop3
ip inspect name inspect_rule ssh
ip inspect name inspect_rule echo
ip inspect name inspect_rule isakmp
no ipv6 cef
ntp master
ntp server 192.5.41.40
ntp server 192.5.41.41
ntp server 192.5.41.42
!
multilink bundle-name authenticated
!
!
!
!
!
!
trunk group POTS
hunt-scheme sequential
!
!
voice call send-alert
voice rtp send-recv
!
voice service pots
!
voice service voip
allow-connections h323 to sip
allow-connections sip to h323
no supplementary-service h450.3
supplementary-service h450.12
no supplementary-service h225-notify cid-update
fax protocol pass-through g711ulaw
h323
h225 h245-address on-connect
call preserve limit-media-detection
modem passthrough nse codec g711ulaw
sip
!
!
!
voice class codec 1
codec preference 1 g711ulaw
codec preference 2 g729r8
!
!
!
!
voice class h323 1
h225 timeout tcp establish 6
!
!
!
!
!
!
!
!
!
!
!
!
voice-card 0
dspfarm
dsp services dspfarm
!
!
crypto pki trustpoint TP-self-signed-********
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-******
revocation-check none
rsakeypair TP-self-signed-*******
!
!
crypto pki certificate chain TP-self-signed-******
certificate self-signed 01
"output omitted, just a bunch of hex"

quit
!
!
username administrator privilege 15 secret 5 **********
archive
log config
hidekeys
!
!
crypto isakmp policy 10
encr aes
hash md5
authentication pre-share
group 2
crypto isakmp key **** address 96.***.***.*** no-xauth
!
!
crypto ipsec transform-set RTRAmagansett esp-aes esp-md5-hmac
!
crypto map amagansett 20 ipsec-isakmp
set peer 96.***.***.***
set transform-set RTRAmagansett
match address RTRAmagansett
!
!
!
ip tftp source-interface FastEthernet0/0
ip ssh source-interface FastEthernet0/0
ip ssh version 2
!
!
!
!
interface Loopback0
no ip address
!
interface Tunnel0
description GRE over IPsec tunnel to Amagansett
ip address 10.0.254.1 255.255.255.0
tunnel

 

[teknojnky]

often times, cable modems are MAC-address locked.

you may need to contact your cable company and give them the MAC address of the cisco wan

 

[overdrive31]

often times, cable modems are MAC-address locked.

you may need to contact your cable company and give them the MAC address of the cisco wan

The modem is not locked in regards to having to inform the cable company of anything. The modem is session locked to an MAC address. All that needs to be done is have the router set to DHCP and reboot the modem. Rebooting the modem can be as easy as unplugging and plugging it back in. Some cable modems have battery backup for voip and use an reset button to reboot because unplugging makes it run off battery and it wouldn't get rebooted. You can force an IP change on cable modems, by simply changing the MAC address on the router/computer and rebooting the modem.

 

[bendsley]

Show your inside and outside interfaces.

All the other crap in your config is useless for this.

However, basic config for cable modem on this router would be (assuming ETH1 is outside):

interface Ethernet1
ip address dhcp
ip nat outside
no ip route-cache
no cdp enable
ip nat inside source list 102 interface Ethernet1 overload

ip classless
ip route 0.0.0.0 0.0.0.0 GATEWAY IP

access-list 102 permit ip 10.10.10.0 0.0.0.255 any