From: Kyle Galusha (kgalusha@xxxxxxxxx)
Date: Wed Aug 30 2000 - 22:56:47 GMT-3
Derek,
I believe ISL is supported on GigE but you will find some switches (e.g., CAT 4
003/6) don't support ISL. As someone stated earlier the CAT6X00 supports ISL
and 802.1Q on trunk ports (Fast and Gig).
Best,
Kyle
At 03:40 PM 8/30/2000 -0400, Derek Small wrote:
>802.1q is supported on GigE, although ISL is not. ISL and 802.1q is
>supported on all Router 100Meg Ethernet interfaces, except for the 1700
>series platform. Using IRB or CRB only lets you combine routing and
>switching of various protocols over several interfaces. The problem that
>you are running into is you have several VLANs defined. VLANs are logically
>isolated networks by definition. Therefore you need some device (logical or
>physical) that will allow you to move traffic between the two VLANs.
>Certainly you could take several switches that are divided into numerous
>VLANs, and plug one connection from each of those VLANs into another switch
>or bridge device that is not devided into VLANS and create one big switched
>network again. But all you have done is bridged your VLANs back into a
>single broadcast domain, or a single switch network. The purpose of
>creating VLANs is to isolate one network segment from another, usually for
>security or broadcast reduction. That means you want to allow traffic to
>flow between the VLANs only through some layer 3 device, a router usually.
>There are three ways to interconnect VLANs with a layer 3 device.
>
>1. Connect one interface from each VLAN to an interface in the router.
>2. Connect a trunk line to the router that supports all the VLANs, then
>break each VLAN back out on the router with logical interfaces
>(sub-interfaces).
>3. Put layer three intelligence in the switch itself. Install an RSM or MSM
>routing engine and define VLAN interfaces for each VLAN.
>
>You could assign secondary IP addresses to an ethernet port on a router and
>then route between the addresses, but how are you going to get traffic from
>all the VLANs into the router? Remember we are trying to use a single port
>on the router here, right? The only way to get traffic from more than one
>VLAN to enter a port on a router is to enable trunking on the switch end of
>that port, thereby sending all VLANs that are permitted on that trunk to be
>sent to the router, or to bridge all the VLANs together and then send
>traffic to the port on the router. If you bridge all the VLANs together
>though, you just defeated any benifit there might have been to creating
>VLANs in the first place.
>
>I think you are getting confused on where VLANs are defined. VLANs are
>defined on switches, networks are defined on routers. Router only use
>subinterfaces to keep VLAN traffic seperated so they can treat the network
>on each VLAN differantly. The only VLAN operation you can do on a router is
>assign a logical port to a specific VLAN, you can't define a VLAN on a
>router. (I suppose you may be able to interconnect two routers with a cross
>over cable and a trunking protocol, but I cannot imagine a situation where
>that would be useful, and I have doubts that it would work anyway).
>
>Derek Small
>CCIE # 5832, Nortel NCSE
>513-703-7059
>dwsmall@fatkid.com
>
>
>----- Original Message -----
>From: Erick B. <erickbe@yahoo.com>
>To: Aaron DuShey <aaron.dushey@dushey-consulting.com>; CCIE (E-mail)
><ccielab@groupstudy.com>
>Sent: Wednesday, August 30, 2000 5:48 PM
>Subject: Re: vlans
>
>
>>
>> >From my knowledge, Cisco only supports trunking (ISL
>> or 802.1q) on 100meg interfaces to date (correct me if
>> I'm wrong - need to do more VLAN work). Some modules
>> support ISL and some 802.1q. If you can't use a
>> trunking protocol then the only other way to route
>> between VLANs is to make the switch-port a member of
>> all the VLANs and multinet the router interface so it
>> has address's for all the networks. Not a pretty
>> solution but it works.
>>
>> - Erick
>>
>> --- Aaron DuShey <aaron.dushey@dushey-consulting.com>
>> wrote:
>> > question-
>> > What other methods are there for routing between
>> > VLANs besides subinterfaces
>> > w/ISL?
>> > Can you use IRB/CRB to do this?
>> > This is on a 3640 FastE interface.
>> > Does this mean that if you don't have a 100MB
>> > interface on a router you can
>> > use IRB to route between the vlans instead?
>> > Little confused here...any help is greatly
>> > appreciated,
>> > The doc cd states-but I am still not completely
>> > clear
>> > Our VLAN Routing implementation is designed to
>> > operate across all router
>> > platforms. However, the Inter-Switch Link (ISL) VLAN
>> > trunking protocol
>> > currently is defined on 100 BaseTX/FX Fast Ethernet
>> > interfaces only and
>> > therefore is appropriate to the Cisco 7000 and
>> > higher-end platforms only.
>> > The IEEE 802.10 protocol can run over any LAN or
>> > HDLC serial interface. VLAN
>> > traffic is fast switched. The actual format of these
>> > VLAN encapsulations are
>> > detailed in the IEEE Standard 802.10-1992 Secure
>> > Data Exchange and in the
>> > Inter-Switch Link (ISL) Protocol Specification.
>> > Our VLAN Routing implementation treats the ISL and
>> > 802.10 protocols as
>> > encapsulation types. On a physical router interface
>> > that receives and
>> > transmits VLAN packets, you can select an arbitrary
>> > subinterface and map it
>> > to the particular VLAN "color" embedded within the
>> > VLAN header. This mapping
>> > allows you to selectively control how LAN traffic is
>> > routed or switched
>> > outside of its own VLAN domain. In the VLAN routing
>> > paradigm, a switched
>> > VLAN corresponds to a single routed subnet, and the
>> > network address is
>> > assigned to the subinterface.
>> >
>> > Aaron DuShey
>>
>>
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