Re: ip alias

From: Bob Sinclair (bsin@cox.net)
Date: Thu May 26 2005 - 09:44:24 GMT-3


Tim,

I like to use the command SHOW IP ALIAS in order to get a short listing of the
IP addresses on each router.

For example:

R1#sh ip alias
Address Type IP Address Port
Interface 192.168.0.100
Interface 50.50.50.1
Interface 172.16.8.1
Interface 172.16.7.1
Interface 172.16.1.1
Interface 172.16.101.1

 I then past the list into notepad, and do a search-and-replace to get rid of

"Interface "

Results in a nice list of IP addresses I can use for my TCL script.

Just to confirm your explanation, I added the following command to R1:

R1(config)#ip alias 192.168.0.105 23

And I was then able to telnet to the 105 address. Here is the subsequent
output:

R1#sh ip alias
Address Type IP Address Port
Alias 192.168.0.105 23
Interface 192.168.0.100
Interface 50.50.50.1
Interface 172.16.8.1
Interface 172.16.7.1
Interface 172.16.1.1
Interface 172.16.101.1

Thanks!

Bob Sinclair
CCIE #10427, CCSI 30427, CISSP
www.netmasterclass.net

  ----- Original Message -----
  From: ccie2be
  To: 'Bob Sinclair' ; '22Cent@gmail.com' ; 'Group Study'
  Sent: Thursday, May 26, 2005 8:11 AM
  Subject: RE: ip alias

  Ray,

  I think this command falls into the "Stupid Router Tricks" category.
  However, nothing in the lab blueprints excludes such things so it could be
  there.

  That said, here are my notes on it.

  Its possible to have a router accept telnet requests to an ip host address
  that doesn't exist on any of the router's interfaces. For example, assume
  that the dns entry for a router is entered with the wrong ip address. If
  you configure ip alias <wrong ip> 23, the router will accept that. (See IE
  lab 4) The wrong ip address should only be wrong in the host portion of the
  address- the subnet should exist on the router. Another possible way to
  achieve the same effect is to use 2ndary addressing on an interface. (See
  IE lab 7)

  Bob,

  Any chance you could post an example of how to use this command to collect
  addresses for a TCL script? Am I missing something obvious cause I don't
  see how this command would help?

  TIA, Tim

  -----Original Message-----
  From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Bob
  Sinclair
  Sent: Wednesday, May 25, 2005 9:25 PM
  To: 22Cent@gmail.com; Group Study
  Subject: Re: ip alias

  Not sure of its intended use. I use it to collect IP addresses for my TCL
  scripts. Seems to minimize unnecessary characters. It also displays
  dynamic
  addresses, those configured via static NAT or DHCP.

  Bob Sinclair
  CCIE #10427, CCSI 30427, CISSP
  www.netmasterclass.net

    ----- Original Message -----
    From: 22Cent@gmail.com
    To: Group Study
    Sent: Wednesday, May 25, 2005 9:15 PM
    Subject: ip alias

    Hi group,
    What is the correct usage of the ip alias command. I was once told it
    can be useful in the lab. Any thoughts?

    TIA
    Ray

    R1(config)#ip alias ?
    A.B.C.D IP address to alias to a port

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