Cisco Support Community
Community Member

Fastethernet Subinterfaces

I am trying to configure IP routing on Fastethernet subinterfaces on a 2621MX router, when I try to assign an IP-Address I get the error message configuring IP routing on a LAN subinterface is only allowed if the subinterface is already configured as part of 802.10, 802.1q or ISL VLAN. The problem is I do not get the option to specify an encapsulation protocol or and VLAN id in subinterface or interface mode. Not sure if I'm missing something.


Re: Fastethernet Subinterfaces

what code are you running ?

Community Member

Re: Fastethernet Subinterfaces



Re: Fastethernet Subinterfaces

what is the feature set i.e. ip ip plus enterprise , this is the letters in the name of the image

Community Member

Re: Fastethernet Subinterfaces

IP Plus

Re: Fastethernet Subinterfaces

loyalty, just to make sure, can you paste the sh version output....

Community Member

Re: Fastethernet Subinterfaces

Here is the output, thanks.

sh ver

Cisco Internetwork Operating System Software

IOS (tm) C2600 Software (C2600-I-M), Version 12.2(17a), RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2003 by cisco Systems, Inc.

Compiled Thu 19-Jun-03 16:35 by pwade

Image text-base: 0x8000808C, data-base: 0x80A14C38

ROM: System Bootstrap, Version 12.2(7r) [cmong 7r], RELEASE SOFTWARE (fc1)

LMGTOR2 uptime is 1 minute

System returned to ROM by power-on

System image file is "flash:c2600-i-mz.122-17a.bin"

cisco 2621XM (MPC860P) processor (revision 0x100) with 59392K/6144K bytes of memory.

Processor board ID JAE072914CC (3699359953)

M860 processor: part number 5, mask 2

Bridging software.

X.25 software, Version 3.0.0.

Primary Rate ISDN software, Version 1.1.

2 FastEthernet/IEEE 802.3 interface(s)

1 Channelized T1/PRI port(s)

32K bytes of non-volatile configuration memory.

16384K bytes of processor board System flash (Read/Write)


Configuration register is 0x2102


Re: Fastethernet Subinterfaces

You're running plain vanilla IOS IP, not IP Plus.

If it were IP Plus, the image name would have an "s" in it, as in "c2600-is-mz.122-17a.bin".

That's the problem.

The size of that IP image is 5,549,180 bytes; size of the IP Plus is 10,283,928 bytes. You might just be able to squeeze both into your 16MB flash. Check to see what's there by running "show flash" or "dir" from the enable prompt.

If you have both, check your startup configuration for a "boot system flash" command that's loading the IP image name instead of the IP Plus.

Once you're running IP Plus, you should be able to specify the LAN encapsulation under the FastEthernet subinterfaces, and then the IP addresses for each.

Hope this helps.

Community Member

Re: Fastethernet Subinterfaces

Thanks works just fine now.

CreatePlease to create content