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Dayton Brown
Asked: 2011-09-23 11:35:16 +0800 CST

Cisco 2948G-L3 as a L2 Switch

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I'm not what you would call a network engineer by any stretch, but I was given a 2948G-L3 switch to use. I'd love to add it to the network, but can't figure out a config that will let it do plain L2 switching. I've googled all sorts of configs but nothing seems to work.

Thanks,

cisco

5 Answers

  1. Your only option on this device would be bridging. It is not a true L2 switch and can never be one.

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  2. Best Answer

    It can be done by creating a BVI (bridge virtual interface) and then assigning the ports you want to switch to the BVI. The BVI still must be assigned an IP address, but if you didn't do that, you couldn't manage the switch.

    The relevant system-level commands are:

    bridge irb
bridge 1 protocol ieee
bridge 1 route ip

    To create the BVI:

    interface bvi 1
ip address ...

    To add an interface to the BVI:

    interface ...
bridge-group 1

    See this link for information about disabling spanning tree and enabling portfast. You may need portfast to get DHCP/PXE to work in some cases.

    Note that the I make no promises about what kind of performance you'll get with this configuration. This is just not what this device was built to do.

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  3. By default, L3 switches only switch out of the box, they don't route out of the box. My suggestion would be to reset the switch to factory defaults and then configure (or not) it accordingly.

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  4. Admittedly I've never meddled with a 2948 but usually on the other L3 switches it is simply a case of shutting down the routing engine:

    Router(config)# no ip routing
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  5. Not sure if this will be working on a 2948-L3, but you could try to do the following:

    interface FastEthernet0/0
 switchport

    If this doesn't work, try to make a bridge-group as David's answer.

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