Router on a stick

[azev]

Just curious if 2500 series router can be setup as a router on a stick on a lab environtment ?

 

[bgroff]

No. You need a router that's capable of 802.1q or ISL encapsulation. The 2500 series is not capable of this.

 

[spidey07]

Originally posted by: bgroff
No. You need a router that's capable of 802.1q or ISL encapsulation. The 2500 series is not capable of this.

and if I recall only 10/100 router ports can do trunking. Something with the chipset used.

Although maybe 12.3 got around that limitation...don't know.

 

[ScottMac]

I believe Spidey is correct, and would like to add that while some 10BASE-T interfaces (and IOS combinations) will accept the commands to trunk, they are not functional.

FWIW

Scott

 

[n0cmonkey]

EDIT: Ok, looks like this is a different definition of "router on a stick."

In case someone is wondering what this is, here's a bit from a pdf google gave me from alliedtelesyn.co.nz:

This How To note will work with routers on software version 2.6.X and above?Router on a stick?, also called one-armed routing, is a term that describes the use of a single multihomed interface of a router to route between multiple subnets.It is commonly used when multiple IP subnets are being used on a single LAN segment. The routersimply has a multihomed interface, with an IP address in each of the subnets being used on the segment. It can thereby participate in all of the subnets, and route between them.

 

[spidey07]

well let's clarigy "router on a stick" then.

it really means a router connected to multiple layer2 instances and routing between them. Routing is really layer3 but layer3 maps DIRECTLY to layer2 in a one-2-one relationship which in turn map to layer1.

So we have one layer 1 interface - ethernet and one layer 2 interface. router on a stick means using some form of tagging to differentiate different layer2 networks...aka trunking. Works great and appeases the network gods.

Multinetting is the EXTREMELY POOR PRACTICE of running multiple layer3 networks on a single layer2 network - having different IP networks on a single interface. This is bad, and should only be used if you really, really, really have to like an ip address migration to provide connectivity while addresses are changed.

so multinetting and "router on a stick" are very different things.

 

[bgroff]

As far as doing RoS on a 10 Mbit interface, it works and has worked since the 12.2/12.2T days. I've used it on 2610s in the lab enough to vouch for it working. Obviously the downfall is much less bandwidth...

 

[spidey07]

Originally posted by: bgroff
As far as doing RoS on a 10 Mbit interface, it works and has worked since the 12.2/12.2T days. I've used it on 2610s in the lab enough to vouch for it working. Obviously the downfall is much less bandwidth...

really!

sweet. Thanks for the clarification.

That was always the hold back for the now defunct 2610s - lack of tagging on their ethernet interface.

 

[azev]

Thanks for the reply guys, I really appreciate it.

I do have a question : My 2501 e0 sub-if doesnt take any encapsulation command, and my router is running IOS 12.2(28). Could this be the hardware limitation of the router it self?

I am working to piece together a CCNP lab and wonder which router I should get. I need the cheapest router that can do every possible scenario/lab so that I can get a couple of them. Any recomendation ?

Thanks

 

[randal]

In my experience you can do dot1q on 10mbit interfaces 2610 with the 12.0+ versions of the T branch, or 12.2+ in general. I ran into a 7202 at a customer site that would let you put in the encaps command on a 10mbit interface, but it wouldn't work (I think they were on 12.0?). I just checked on a 12.2(5) 2524 I happen to have laying around and it will NOT allow me to put in any encaps options:

c2524#conf t
Enter configuration commands, one per line. End with CNTL/Z.
c2524(config)#int e0.1
c2524(config-subif)#en?
% Unrecognized command

I read somewhere once upon a time that a 2500-series router will do ISL, but were never able to do dot1q. 2600s, however, can do it without issue. $.02

Edit: I just did some googling and the 2500s don't do any sort of L2 encapsulation, period. They support subinterfaces ... this is interesting as well:

c2524#conf t
Enter configuration commands, one per line. End with CNTL/Z.
c2524(config)#int e0.1
c2524(config-subif)#ip address x.x.x.x 255.255.255.0

Configuring IP routing on a LAN subinterface is only allowed if that
subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q, or ISL vLAN.

c2524(config-subif)#encaps ?
% Unrecognized command
c2524(config-subif)#int e0
c2524(config-if)#encaps?
% Unrecognized command

Incredibly, the encaps command isn't available anywhere on that router, but subinterfaces are? wtf?

 

[azev]

You know what randal, I was getting the same error on my 2501 with IOS 12.2(28). Thats led me to post question in this forum hehe..

 

[bgroff]

Randal -

The ethernet subinterfaces on a 2500 are for different IPX encapsulation types. Unlike TCP/IP, IPX could use arpa/novell-ether/sap/snap. So in order to have multiple ipx networks on the same ethernet interface with differing encapsulation types, you'd configure it via sub interfaces.

 

[randal]

I took a look at the 2524 I was testing doesn't seem to do IPX at all. Unfortunately, I'm a total IPX noob, but what you're saying jives with what my hazy memory tells me. That whole subif but no 802.1q kinda made me wonder -- thanks bgroff

 

[azev]

Does anyone here know if cisco 2500 series support full duplex on its E0 interface ?

 

[IEC]

Ouch, my head hurts.

 

[w0ss]

The 2500 series does half duplex only.