Catalyst 2950 DHCP and Static IP

[pholdcroft]

Hi,

I've installed a 2950 into my domestic LAN from a site that was no longer using it. I've removed the existing config, it was working in conjunction with an Allied Teleysn AR-440 router for handling the incoming WAN connection and DHCP requirements. I have a Linksys router at home and have run out of wired ports so I'm hoping to replace it with the 2950.

I have a static address from my ISP in the range 80.249.x.x with a subnet of 255.255.255.224. I then have a 192.168.1.x local LAN with several devices also assigned static addresses. Is there a way of configuring say FastEthernet 24 to the required static IP on VLAN 1 and then have the switch provide correct local LAN addresses with access to VLAN 1?

Thanks for the help,

Pierce

[andtoth]

Hi Pierce,

You can use the switch as a DHCP server, for the configuration steps I would recommend to check the following documentation.

Configuring DHCP on Cisco IOS 12.1

http://www.cisco.com/en/US/docs/ios/12_1/iproute/configuration/guide/1cddhcp.html

If you want to assign a static IP for the switch in Vlan1, use the ip address command in interface configuration mode for interface Vlan1 as follows.

conf t

interface vlan1

ip address x.x.x.x y.y.y.y

no shutdown

By default, all ports should be in vlan 1 already, however, you can change it per-port by using the switchport mode access command in conjunction with the switchport access vlan 1 command under interface FastEthernet0/24 configuration.

Please note that the 2950 is not capable of IP routing nor IP NAT (Network Address Translation), therefore it cannot provide internet connection on it's own to clients with a private (192.168.x.x) IP range without a router in your network.

Best regards,

Andras

[cadet alain]

Andras,

You can use the switch as a DHCP server

How can a L2 device be a DHCP server?

[andtoth]

Hi,

A DHCP server is basically allocating IP addresses to clients on the subnet. Simplified, it is just a running process/application which is monitoring broadcast packets on the network and sending replies which contain the allocatable IP address. The DHCP server does not route packets, it's not the default router usually. The 2950 switch is still a L2 device and cannot route packets but can act as a simple DHCP server for your subnet.

In SOHO and small home routers, usually the DHCP server and router itself is integrated in the same device. In those cases, the DHCP server is still just an application and when it allocates an IP address, it sets the default router IP to be the device itself.

http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

Andras

[cadet alain]

Hi,

I learned something new today and I'm happy but then I looked in Cisco feature navigator for dhcp server support and I found no 2950 but it begins with 2955.

Regards.

[andtoth · Accepted solution]

Hi,

Apologies, you are right, DHCP server is only available in 2955 switches. I double-checked in the configuration guide:

The DHCP server feature is only available on Catalyst 2955 switches.

http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_22_ea11x/configuration/guide/swdhcp82.html

Best regards,

Andras

[pholdcroft]

Thanks Andras and Cadetalain,

I guess I'll just keep the current router in position for NAT and DHCP!

Regards,

Pierce