Re: 127.x.x.x

William,

I seem to recall something in the 127/8 space being used internally for NTP as well...I would have to look up the exact address

Sent from my Verizon Wireless BlackBerry

Regards,

 Joe Astorino - CCIE #24347
Sr. Technical Instructor - IPexpert
Mailto: jastorino_at_ipexpert.com
Telephone: +1.810.326.1444
Live Assistance, Please visit: www.ipexpert.com/chat
eFax: +1.810.454.0130

IPexpert is a premier provider of Self-Study Workbooks, Video on Demand, Audio Tools, Online Hardware Rental and Classroom Training for the Cisco CCIE (R&S, Voice, Security & Service Provider) certification(s) with training locations throughout the United States, Europe, South Asia and Australia. Be sure to visit our online communities at www.ipexpert.com/communities and our public website at www.ipexpert.com

-----Original Message-----
From: William McCall <william.mccall_at_gmail.com>
Date: Tue, 20 Apr 2010 22:53:16
To: ccie.unnumbered<ccie.unnumbered_at_gmail.com>
Cc: ccielab<ccielab_at_groupstudy.com>
Subject: Re: 127.x.x.x

No.

For at least 2 reasons:

1) RFC 1700 [1] and RFC 3330 [2] both specify that the 127.0.0.0/8
should never appear on any network anywhere. Cisco complies with this
directive [3] in 12.4T (and, I'm willing to bet, most any other
version of IOS but the old timers can tell me about how 11.0 allowed
this)

2) These loopback addresses are used internally for, primarily,
service modules and linecards (anyone, is there any other place this
is used?) and would most likely break stuff. For example, attaching to
a line card on the 12K GSR (IOS, not sure about XR) results in a funky
telnet connection to an address like 127.0.0.17.

For the scenario you proposed on your Linux box before, you can create
a sub interface on the loopback interface. Example:

ifconfig lo:0 192.168.12.1 netmask 255.255.255.0

And now you have a new network for handling your terminal server.

HTH

-- 
William McCall, CCIE #25044
[1] http://www.faqs.org/rfcs/rfc1700.html
[2] http://www.faqs.org/rfcs/rfc3330.html
[3]http://www.cisco.com/en/US/customer/docs/ios/ipaddr/configuration/guide/iad_config_ipadd_ps6441_TSD_Products_Configuration_Guide_Chapter.html
On Tue, Apr 20, 2010 at 10:27 PM, ccie.unnumbered
<ccie.unnumbered_at_gmail.com> wrote:
> Is there a way that 127.x.x.x can be assigned to any interface on a Cisco
> router/switch?
>
> Thanks,
> Jack
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
Blogs and organic groups at http://www.ccie.net