Cisco 2621 on Comcast Cable?

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Socialoutcast
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Posts: 3
Joined: Wed Jan 03, 2007 4:50 pm

Cisco 2621 on Comcast Cable?

Post by Socialoutcast »

Ok guys I am feeling real dense and just can not get my 2621 working on comcast cable. It's all DHCP so it should be rather easy but I just can't get it. I am use to working on routers that use all static IP and have not had to setup a 2621 for NATing. I have blown my config away to start from scratch. Just in case you are not up on older Cisco gear the 2621 has 2 Fast Ethernet ports. I am not running any wics on the router as I don't think I need to as I don't use PPPoE. Any and all help including links to example would be great. Not saying I am a god at Cisco but I know enough to get by. Thanks in advance.
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greEd
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Joined: Wed May 09, 2001 12:00 am
Location: Maryland

Post by greEd »

Have you been able to obtain a address using dhcp on your external interface at all?
Using something like this should get you a external address:

Code: Select all

interface Ethernet0
 ip address dhcp
 no ip unreachables
 no ip proxy-arp
 no cdp enable
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YeOldeStonecat
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Location: Somewhere along the shoreline in New England

Post by YeOldeStonecat »

Yes DHCP on the WAN interface. But first..you MUST power off the cable modem for several minutes, so it will "forget" the MAC of the prior device that was connected to it. If you skip this step...it will not recognize the MAC of the Cisco's WAN port..thus not release a legit public IP to it, but rather something like 192.168.100.xxx.

If you have Comcast voice over IP phone service...you'll have an MTA instead of a regular modem, so you also need to remove the battery in the MTA when powering it off..so it will "forget" the MAC.

Then..power up your new router...connected to the modem...power up the modem, allow it to "synch up". Once it's synched up after a minute...power cycle your router so it will pull a good IP and DNS info. Then release/renew workstations so they'll get it. Should be good to go.
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Socialoutcast
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Joined: Wed Jan 03, 2007 4:50 pm

Post by Socialoutcast »

HAHAHAHA you know what. I had all the code right but forgot to turn the stinkin modem off. I knew I was going crazy. Thanks guys.
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Socialoutcast
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Joined: Wed Jan 03, 2007 4:50 pm

Post by Socialoutcast »

So I am running FA0/0 as the WAN port and FA0/1 as the LAN. The DHCP pool is working for the Lan but I need to try and get the modem working later as I am still at work. Then all I should have to do is set a default route from FA0/1 to FA0/0. Wait maybe I just have to do the Nat part of it. I forget the long command but it's at home on my desktop I'll post my config later if I have more issues.
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aphexnexus

Post by aphexnexus »

I am having a similar issue. Running a 3725 here at home and everything was running just fine. I had to shut the router down for a bit to swap around power cords and upon reboot it will not obtain an IP address. I've cycled my cable modem more times than I care to remember, and have tested with my laptop to confirm that it will still hand out an address. Of course it will to a PC :( . I have a matching config for my external IP as greEd has listed above. I feel that Comcast might be at fault here, but would like to know where to start with my questions for him. Here is my running config. This all was working when I came home from work this evening.

sh run
Building configuration...

Current configuration : 4061 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname VoIP-Ashburn-VA
!
boot-start-marker
boot system flash c3725-jk9s2-mz.123-22.bin
boot-end-marker
!
!
memory-size iomem 15
clock timezone EST -5
clock summer-time EDT recurring
no network-clock-participate wic 0
no aaa new-model
ip subnet-zero
!
ip dhcp excluded-address 192.168.10.1 192.168.10.50
!
ip dhcp pool PC
network 192.168.10.0 255.255.255.0
default-router 192.168.10.1
dns-server 68.87.73.242 68.87.73.226
!
ip dhcp pool Aphex
host 192.168.10.5 255.255.255.0
client-identifier 0100.1617.d89e.10
client-name Aphex
default-router 192.168.10.1
!
ip cef
!
voice service voip
no allow-connections any to pots
no allow-connections pots to any
allow-connections h323 to h323
!
controller T1 0/0
framing sf
linecode ami
!
interface FastEthernet0/0
ip address dhcp
ip access-group Inbound in
ip access-group Outbound out
ip nat outside
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 192.168.10.1 255.255.255.0
ip nat inside
duplex auto
speed auto
!
ip nat inside source list 100 interface FastEthernet0/0 overload
ip nat inside source static tcp 192.168.10.5 62202 interface FastEthernet0/0 62202
ip nat inside source static udp 192.168.10.5 5900 interface FastEthernet0/0 5900
ip nat inside source static udp 192.168.10.5 6112 interface FastEthernet0/0 6112
ip nat inside source static tcp 192.168.10.5 22 interface FastEthernet0/0 22
ip nat inside source static tcp 192.168.10.5 6969 interface FastEthernet0/0 6969
ip nat inside source static udp 192.168.10.5 6969 interface FastEthernet0/0 6969
ip nat inside source static udp 192.168.10.5 49152 interface FastEthernet0/0 49152
ip nat inside source static tcp 192.168.10.5 49152 interface FastEthernet0/0 49152
ip nat inside source static tcp 192.168.10.5 20 interface FastEthernet0/0 20
ip nat inside source static tcp 192.168.10.5 21 interface FastEthernet0/0 21
ip nat inside source static udp 192.168.10.5 3783 interface FastEthernet0/0 3783
ip nat inside source static udp 192.168.10.5 6667 interface FastEthernet0/0 6667
ip nat inside source static udp 192.168.10.5 6515 interface FastEthernet0/0 6515
ip nat inside source static udp 192.168.10.5 6500 interface FastEthernet0/0 6500
ip nat inside source static udp 192.168.10.5 62202 interface FastEthernet0/0 62202
ip http server
ip http authentication local
no ip http secure-server
ip http path flash:
ip classless
!
ip access-list extended Inbound
evaluate mypackets
permit udp any 0.0.0.0 255.255.255.0 eq 62202
permit tcp any 0.0.0.0 255.255.255.0 eq 62202
permit udp any 0.0.0.0 255.255.255.0 eq 6112
permit udp any 0.0.0.0 255.255.255.0 eq 6969
permit udp any 0.0.0.0 255.255.255.0 eq 3783
permit udp any 0.0.0.0 255.255.255.0 eq 6667
permit udp any 0.0.0.0 255.255.255.0 eq 6515
permit udp any 0.0.0.0 255.255.255.0 eq 6500
permit tcp 0.0.0.0 255.255.255.0 0.0.0.0 255.255.255.0 eq 22
permit tcp host 75.134.184.100 0.0.0.0 255.255.255.0 eq 22
permit tcp host 76.226.172.225 0.0.0.0 255.255.255.0 eq 22
permit tcp host 75.134.184.100 0.0.0.0 255.255.255.0 eq ftp
permit tcp host 75.134.184.100 0.0.0.0 255.255.255.0 eq ftp-data
permit tcp host 76.226.172.225 0.0.0.0 255.255.255.0 eq ftp
permit tcp host 76.226.172.225 0.0.0.0 255.255.255.0 eq ftp-data
ip access-list extended Outbound
permit tcp any any reflect mypackets
permit udp any any reflect mypackets
permit icmp any any reflect mypackets
access-list 100 permit ip any any
!
!
telephony-service
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
!
ntp clock-period 17180543
ntp server 81.19.16.225
end

Hope someone can shed some light on this.

Thank you,
Justin
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