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Inter-VLAN routing configurations (Cisco Catalyst 2960)

Posted on 2016-10-28
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Last Modified: 2016-10-28
I have a Catalyst 2960 that has some L3 capabilities. I have other switches throughout my network that are also L3 capable (all Cisco). I have very little skill in the Cisco IOS and need to ask some basic questions for which I can't seem to find the answer in my searches.

  1. When doing L3 switching with inter-VLAN routing, do all other switches need to come back to a primary L3 switch?
  2. If no to #1, then what if I have multiple groups of switches that are inter-connected with the primary L3 switch connecting to only one of them?

I have uploaded a diagram of what I inherited.  I emphasize "inherited" because I already know that I have too many separations between some switches and am planning to fix that. The meat of my question is this:

Can someone please help me understand where all of the L3 logic needs to be? Does only one switch act as the routing switch, or do they all have to possess the same routing configuration? I know all switches have to be VLAN-capable switches, but do they all have to be L3?
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Question by:Shane Kahkola
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by:SIM50
SIM50 earned 250 total points
ID: 41863879
First of all, 2960 is L2 switch only.  You can set IP to VLAN interface but it is done mostly for the management access.
1. To allow VLANs communicate with each other, they need to connect to either a router or L3 switch where VLAN interfaces (gateways) are setup.
2. You can have only one switch do the routing but that really depends on the size of the network. In large networks, there are multiple aggregation layers and routed uplinks.
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by:Shane Kahkola
ID: 41863902
The 2960 is not L2 only.  It depends on the model.  It is basically L2, but has other features.
From Cisco's specs:
Cisco Catalyst 2960-XR models also offer:
  • Power resiliency with optional dual field-replaceable power supplies
  • IP Lite Cisco IOS software with dynamic routing and Layer 3 features

With that in mind, Am I to assume it cannot act as the routing switch?
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Predrag Jovic earned 250 total points
ID: 41863903
2960 can act as L3 switch (16 static routes maximum), not all 2960 switches support option.
When doing L3 switching with inter-VLAN routing, do all other switches need to come back to a primary L3 switch?
No, but typically how it is done. Simple is good.
If no to #1, then what if I have multiple groups of switches that are inter-connected with the primary L3 switch connecting to only one of them?
But you will have to configure VLAN interface somewhere and it will be used as default gateway...
Typically you need to change proper SDM template with
>en
# conf t
(config)# show sdm prefer lanbase-routing

to be able to enable routing you need to reload switch and then issue
(config)# ip routing
Does only one switch act as the routing switch, or do they all have to possess the same routing configuration?
Typically you will end up with one switch act as router, the reason is location of default gateway, but it can be configured differently.
IP Lite Cisco IOS software with dynamic routing and Layer 3 features
I did not know about dynamic routing part. :)
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by:SIM50
ID: 41863927
You're right. 2960-XR does have some L3 support.
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by:Predrag Jovic
ID: 41863935
2960, 2960-s, 2960-x too, it is old feature ...
:)
However, 2960-XR have even new abilities.
Catalyst 2960-XR Switch Routing Configuration Guide, Cisco IOS Release 15.0(2)EX1
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by:SIM50
ID: 41863954
Never would of thought to use them as L3 switches... Interesting non the less.
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by:Shane Kahkola
ID: 41863960
Thank you for all of the input!
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by:Predrag Jovic
ID: 41863963
You can now set up parameters for the selected routing protocols as described in these sections:

    RIP
    OSPF,
    EIGRP
    Unicast Reverse Path Forwarding
    Protocol-Independent Features (optional)
This is my equivalent of dirty talk. :)
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by:Predrag Jovic
ID: 41863966
Check configuration details on the link for 2960-XR since there are a lot of new things added, so configuration of switch for routing can be different from I wrote above.
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