what function can a 2501 router possibly serve?

Unanswered Question
Jan 19th, 2008

obviously i'm a newb. but i'm pulling my hair out trying to understand cisco. in order to figure things out i bought a cheap 2501 router. and i have no clue what its for.

#1. it has no ethernet port. So it must not go on a network? No thats untrue! the AUI port has a tranceiver you can buy to get it onto the network. But that's all the AUI port can do. So instead of putting an ethernet port they put an AUI port. Great thanks, the tranceiver costs more than the whole router! why didn't cisco put a ethernet port to begin with? whats so much better about having a AUI port?

#2 You cannot configure subinterfaces on the 2501. ie you can't do e0.1 or e0.2 why? because there is no encapsulation command for subinterfaces and it wont let you assign ip addressess to subinterfaces until you set an encapsulation method. So if you ever thought "router on a stick" WRONG, 2501 has no capability of doing that. its not compatible with vlans period.

#3 "but it has 2 serial ports", so what? i can connect to another router? this lets me do what? share router resources while at a throughput cost? or is this so i can give my router another AUI port,err, i mean ethernet port? why not just give it another ethernet port then? obviously cisco thought serial>ethernet and aui>ethernet but i don't understand their thought process at all on that!

#4 again with only 1 ethernet port you can't connect one end of this router to the internet, and the other end to your lan, theres not enough ports. so forget saying you use it as a firewall or special ACL's. how would the topology look? is your internet connect to a switch which then goes to your 2501? then your 2501 filters and sends it back to the switch? won't the switch just broadcast everything to begin with essentially bypassing the router anyways? or would you hook this router up next to a router already, and if thats the case then why not put a firewall on that router, why introduce the 2501. it's a stub network and its pointless in any topology.

so... wtf is the point of the 2501. obviously i'm missing a HUGE part of cisco routing. i know i'll smack myself in the head for not thinking of it. but grrr i'm so confused, what in the world is this thing used for!?

I have this problem too.
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shahimkhan Sun, 01/20/2008 - 02:21

Dear Friend,

2501 is a router from a different age, it has lived its life.

You better make into a table stand or a keep it as a antic piece.

will fetch you good money in some years to come

Hi There

In answer to your questions, there is quite a lot you can do with a 25xx routers. Granted a single 2501 router is not much use, but if you had a couple of them attached together and maybe 1 26xx, the possibilities are huge. See the attached file for what my original Lab looked like.

As the previous poster has stated, the 2500 series routers are from a time where 10mbps LANs were cutting edge. Each 25xx router would mostly look after routing 1 LAN network/subnet to the rest of the LAN or WAN.

My Initial CCNA home practice lab was made up of 4 25xx routers and 1 26xx router. With these routers I could configure a Frame Relay network, direct serial connections, run RIP, IGRP, EIGRP and OSPF, configure ISDN (with the help of an ISDN simulator). Admittedly, ROAS was not available on the 25xx routers, but I had the 26xx for that with switches capable of VLAN's.

The reason that the 2501's Ethernet port (AUI connector) cannot do ROAS is because it only runs at 10mbps/half duplex. So even if the interface was an RJ45 interface it still would not be able to provide ROAS functionality.

The 25xx routers were quite cheap and when maxed out with DRAM & Flash (16mb of each), they could run IOS 12.3. I am quite grateful to the 25xx routers for providing me with a low cost option which allowed me to practice the hands on skills required to pass my CCNA.

And today even though my home lab has evolved to meet the requirements of my CCNP studies, my 25xx routers are still in the mix and working like a charm.

See My current Lab here http://homepage.eircom.net/~keeleym/home-Lab2.jpg

So in my opinion if you look positively at what you can do with your 2501 instead of what you cannot do, I think you will be pretty surprised at just how useful it actually is.

Best Regards,


virajmendis Mon, 02/04/2008 - 23:33


I tried to use 2501 AUI interface for Ethernet connection. Instead of transceiver, i used DB15 male connector directly connected with RJ 45 female connector with 4 wire connection. when i connected cable to RJ 45 female connector by creating loop, that interface getting up. But when try with the switch, that interface protocol down.

If any experience in this case, write to me soon.

Kevin Dorrell Tue, 02/05/2008 - 02:32

That can never possibly work. The electrical signals on an AUI are completely different from the RJ45. You might even have toasted your switch, or your AUI port.

How did you decide on the pin correspondence?

You need a transceiver.


Kevin Dorrell


Joseph W. Doherty Sun, 01/20/2008 - 10:41

The 2501 was often a small branch office WAN router. You connected its LAN interface to the (usually only one) local LAN subnet and its WAN interface to a link that connected back to HQ. Its software and hardware support are not what you would expect from todays branch routers, but in its time, it was quite sufficient.

Richard Burts Sun, 01/20/2008 - 19:19


You bought an old router that was quite cheap. One reason it was cheap is because of some of its limitations. Yes you need a transceiver for its Ethernet port (and that does makes it more expensive) but its Ethernet works and you can learn good things from it or use it to route onto an Ethernet subnet.

Yes it has only a single Ethernet. If you want dual Ethernets then you should have looked for a different model of 2500 that has dual Ethernet.

No it can not configure subinterfaces on the Ethernet. If that is a requirement then you made a poor choice.

But I like the answer from Michael. The 2500 is a good, plain, serviceable router that can perform many good functions in a lab environment.



mvanmuyen Thu, 01/31/2008 - 00:36


I've used 2500's for years until just recently. The trick is get another 2501, and set them back to back using serial V.35 cables. Male and female, set clockspeed on one of the sides, I believe the male side (if you don't know male from female just config the clock rate on either side, one after another of course). The serial interface should come up.

Now you have 2 10 mbit/half duplex ethernet interfaces to play with. I know I've learned a great deal from this setup. You can do all that makes Cisco Cisco, even dynamic routing as in EIGRP, OSPF and BGP, multicast routing, (IpSec and GRE) tunnelling, IOS firewalling and what not. Be prepared you can only run 12.3 as IP base due to mainly flash capacity limitations but that also goes for DRAM memory. But within 12.1 and to a lesser extent 12.2 there is lots that will run, very suitable for a n00b as we all once were to learn about IOS.

Good luck with finding another 2501 and V35 serial cables (I won't sell you mine! too valuable)and have fun.


yumologycccp Tue, 02/05/2008 - 12:38

Ok after time I have in fact found use for this. But by itself it serves very little use in a topology. You absolutely need another router to do anything. The greatest part of the 2501 is that its SUPER cheap (I only paid $10) and with that you get your very own router to mess with the IOS and configure it anyway you want, being a great tool for passing the CCNA.

The problem that i had before is trying to understand what cisco was thinking making a router that is useless by itself, you in fact need trancievers and another router to make this work at all. why couldn't cisco make it work by itself i'll never understand.

Kevin Dorrell Tue, 02/05/2008 - 17:31

"But by itself it serves very little use in a topology. You absolutely need another router to do anything." Sorry, but that made me chuckle.

Alexander Graham Bell invented the first telephone, but it wasn't much use until someone invented the second one.

You must think back to the days when the 2501 was designed. At that time, not all networks were using RJ45 and UTP cabling. Most were BNC coax, or even the old yellow cable and vampire connectors. LAN switches did not exist yet - it was hubs if you were lucky, or shared coax segments if you weren't. (Who's stolen the terminator again?)

The AUI was designed to take a variety of different media transceivers. It also meant that the user did not have to replace his very expensive router when he finally installed his new "structured cabling" network.

Kevin Dorrell



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