RouterNotes.com

One of the pains about Cisco is that once you enter the configuration prompt, you can’t show the active configuration without leaving the configuration prompt. Juniper has had this ability for some time and in recent IOS codes, Cisco has finally caught up with the ‘Do’ command. For example:

RouterA#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterA(config)#interface vlan 5
RouterA(config-if)#do sho run interface vlan 6
Building configuration…

Current configuration : 98 bytes
!
interface Vlan6
description Conn To Core
ip address 10.10.10.1 255.255.255.252
end

Thankfully, Microsoft included the ability to resize partitions in Vista without wiping all of the data on a hard drive. The developers may not have intended this as a back door to be able to reinstall your favorite reliable friend, Windows XP, but it certainly works that way. Lifehacker has great notes on partition resizing.

Previous to Vista, a program like Partition Magic was needed to resize and create partitions without reformatting. Vista hasn’t gotten quite the adoption rate that Microsoft was hoping for, mainly due to all of the problems with the new operating system. New computer buyers are especially affected since most new computers come with Vista preinstalled. Wiping a drive and reinstalling XP can be difficult in the because all the needed device drivers may not be available or work properly.

Conventional wisdom says that you have to use four IP addresses for a point to point network where two routers face each other like a T1 connection because one address is used by the network address and one address is used by the broadcast address in addition to the two addresses used by each router. The breakdown looks something like this:

C:\>whatmask 10.10.10.1/30

————————————————
TCP/IP NETWORK INFORMATION
————————————————
IP Entered = ………………: 10.10.10.1
CIDR = ……………………: /30
Netmask = …………………: 255.255.255.252
Netmask (hex) = ……………: 0xfffffffc
Wildcard Bits = ……………: 0.0.0.3
————————————————
Network Address = ………….: 10.10.10.0
Broadcast Address = ………..: 10.10.10.3
Usable IP Addresses = ………: 2
First Usable IP Address = …..: 10.10.10.1
Last Usable IP Address = ……: 10.10.10.2

Note that the subnetting program used here shows only two usable IP address even though we have used four addresses with a CIDR Mask of /30. But RFC 3021 calls for combining the router address and either the network or broadcast address to use only two addresses total with a CIDR mask of /31.

Please note that older routers may not support RFC 3021.