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intervlan routing and subinterfaces

I'm setting up a trunk port on a 2924 switch thats connected to a 7206vxr...

On the router, fa0/0 has several secondary ips listed under it.. In moving over to a trunk port which would be "better practice". To make one sub interface per vlan w/ lots of secondary ips OR several different subinterfaces one for each ip..

Example..

interface FastEthernet0/0.1

encapsulation isl 2

ip address x.x.x.x 255.255.255.0

ip address x.x.x.x 255.255.255.0 secondary

ip address x.x.x.x 255.255.255.0 secondary

ip address x.x.x.x 255.255.255.0 secondary

or

interface FastEthernet0/0.1

encapsulation isl 2

ip address x.x.x.x 255.255.255.0

interface FastEthernet0/0.2

encapsulation isl 2

ip address x.x.x.x 255.255.255.0

interface FastEthernet0/0.3

encapsulation isl 2

ip address x.x.x.x 255.255.255.0

interface FastEthernet0/0.4

encapsulation isl 2

ip address x.x.x.x 255.255.255.0

2 REPLIES

Re: intervlan routing and subinterfaces

Hi,

if you want to route between VLANs, you need a subinterface in each VLAN on the router side, i.e.:

interface FastEthernet0/0.1

encapsulation isl 1

ip address x.x.x.x 255.255.255.0

interface FastEthernet0/0.2

encapsulation isl 2

ip address x.x.x.x 255.255.255.0

interface FastEthernet0/0.3

encapsulation isl 3

ip address x.x.x.x 255.255.255.0

interface FastEthernet0/0.4

encapsulation isl 4

ip address x.x.x.x 255.255.255.0

If you put several secondary IPs on one subinterface (as you mentioned) they would be all in the same VLAN and you wouldn't be able to route between VLANs.

HTH,

Milan

Bronze

Re: intervlan routing and subinterfaces

If you are creating vlans, then you def. need subinterface with right vlan number. In the above subinterface config, you put encap isl 2 under every subinterface, that would not work. every subinterface suppose to belong to different vlan.

If you put all the networks under one subinterface then it would only belong to same vlan which in your case 2 but on different networks.

For your ref,

http://www.cisco.com/warp/customer/473/50.shtml

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