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Egghead
@phonoscope.com

Egghead

Anon

[Connection Sharing] Connect Cisco 2950 to Netgear ADSL CAble Modem

I am attempting to connect a cisco 2950 switch to my cable modem. I set the cable modem up for static addressing. It has an ip of 10.10.0.1. I created vlan 20 for my LAN and vlan 99 for my trunk. Here is my setup for the interfaces on the switch:

Int fa 0/24
switchport mode trunk
switchport trunk native vlan99
end

Int fa 0/23
switchport mode access
switchport access vlan 20
end

int vlan 99
ip address 10.10.0.2/24
end

ip default-gateway 10.10.0.1

I assigned my pc plugged into port 23 an ip of 10.10.0.3 for my first computer. I cannot get out to the internet.What could be my issue?
HELLFIRE
MVM
join:2009-11-25

HELLFIRE

MVM

Dumb question, is the cable modem in router / gateway mode or in bridge mode? How I differentate
between the two is in the first, it's likely handling DHCP / NAT functions and getting the public
IP address. The 2nd it just converts coax to ethernet and you plug in your own gear to get the
public IP address.

2ndly, if you take the switch out of the equation and plug a PC directly in, does it work?

Regards

ropeguru
Premium Member
join:2001-01-25
Mechanicsville, VA

ropeguru to Egghead

Premium Member

to Egghead
could you supply a sh run? What have you setup for the actual routing between the two VLAN's? Been so long since I even looked at a 2950, I cannot remember if it even has built in routing capability.

Well, just found the answer to my own question:

Q. Can Cisco Catalyst 2950 Series Switches be upgraded to enable IP routing?

A. No. None of the Cisco Catalyst 2950 Series Switches can be upgraded to enable IP routing. Cisco Catalyst 3560 and 3750 Series Switches can enable IP routing.

So in short, you cannot do what you want with the 2950.
pb2k
join:2005-05-30
Calgary, AB

pb2k to Egghead

Member

to Egghead
I assume you have a crossover cable if required?
What are you trunking to? Most cable modems don't support dot1q trunks, so you should actually set up the connection to your cable modem as an access port on vlan 20.

You also can't have your management address on vlan 99, in the same subnet as your lan in vlan 20. Putting your management interface on your trunk native vlan is hardly better than leaving it on vlan 1.
hardly
Premium Member
join:2004-02-10
USA

hardly to Egghead

Premium Member

to Egghead
Pardon my ignorance, but what is an ADSL CAble Modem?

ropeguru
Premium Member
join:2001-01-25
Mechanicsville, VA

ropeguru

Premium Member

There is no such thing. Just goes along with the lack of knowledge of how VLAN's and subnets work.
hardly
Premium Member
join:2004-02-10
USA

hardly

Premium Member

Do I take that to mean that a subnet is a net that submerges?
/sarcasm

Egghead
@107.77.64.x

Egghead to pb2k

Anon

to pb2k
I put vlan 20 on interface 24 to my modem and now it works. Thanks for the help.
HELLFIRE
MVM
join:2009-11-25

HELLFIRE to Egghead

MVM

to Egghead
Modem doesn't understand dot1q tags... problem solved

So remove all vlan / trunk references in your config, plug in, and enjoy!

Regards