Configuring InterVLAN Routing and ISL Trunking on 2621 Router

Discussion in 'Cisco' started by Peter, Jan 6, 2004.

  1. Peter

    Peter Guest

    I followed the document - 'Cisco - Configuring InterVLAN Routing and
    ISL/802.1Q Trunking on Catalyst 2900XL/3500XL2490/2950/2970' Switches
    Using an External Router'. Everything was fine until I tried to
    configure ISL encapsulation on the router's Fastethernet
    sub-interfaces. The command 'encapsulate' didn't exist when in
    subinterface mode.

    The Catalyst is a 3524 and is running the following IOS:
    Cisco Internetwork Operating System Software
    IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version 12.0(5)WC7,
    E (fc1)-+

    And the Router is a 2621 and is runing:
    Cisco Internetwork Operating System Software
    IOS (tm) C2600 Software (C2600-I-M), Version 12.0(3)T3, RELEASE
    SOFTWARE (fc1)


    1. Does the IOS version of my router support ISL encapsulation? If
    so, can you tell me how to configure it.

    Additional Information:

    I have defined three VLANs on the switch. They are as follows:

    ? Does VLAN1 have to exist?

    ? I want traffic to be routed between VLAN10 and VLAN20. What is the
    best way to accomplish this?

    ? The router has two FastEthernet ports and one Ethernet port. Do I
    have to place one FastEthernet port in each VLAN and connect the
    Ethernet port to the exterior router?

    I realize that it may sound a bit confusing, but any assistance would
    be appreciated.
    Peter, Jan 6, 2004
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  2. Peter

    Jeroen Guest

    I've this configuration, you probaly do not hav ethe right IOS, IP-Plus, I
    think you nedd.
    Routing between VLan, like my configuration, is default because both
    IP-ranges (172.16.81 and 172.16.81) are directly connected. (show ip route)

    Connect your switch to your router and configure your switch port in
    switchport mode trunking
    and your router- fa-port like this:

    (I've used dot1Q encapsulation, nbut you can use isl if your switch (and
    router) supports it
    interface FastEthernet0/0
    no ip address
    speed 100
    interface FastEthernet0/0.1
    desc vlan 81
    encapsulation dot1Q 81
    ip address

    interface FastEthernet0/0.2
    desc vlan 82
    encapsulation dot1Q 82
    ip address


    Jeroen, Jan 6, 2004
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  3. :VLAN1

    :? Does VLAN1 have to exist?

    Yes. You cannot delete VLAN1 -- but you don't need to have
    assigned it an IP address, and you don't need to use it as
    the management VLAN.
    Walter Roberson, Jan 6, 2004
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