Frame-Relay is one of the core concept of networking and nowadays it is one of the under appreciated part on modern networking.
I am just going to go over how to configure it using 4 Routers and one will act as a Frame-Relay cloud.
Before I go ahead and explain the configuration, You can see the below diagram which represents the physical topology.
As you can see, FRS is connected via…
Serial 1/1 to R1 Serial 1/0
Serial 1/2 to R2 Serial 1/0
Serial 1/3 to R3 Serial 1/0
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If you want to jump between servers without any password authentication but you still need security here is what you have to do.
There are two ways of achieving this:
On Debian/Ubuntu you can just type:
$ cd $HOME
~$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key:
Press Enter each question and you will have a pair of keys ready to use.
You will be asked for a passphrase but if you do not want to insert anything just leave it blank.
This procedure will create one private and one public key.
$ ls .ssh/
id_rsa id_rsa.pub known_hosts
The private key must be secured on your box whereas the public key can be copied across
~$ ssh-copy-id -i .ssh/id_rsa.pub 192.168.1.30
At this time you will be asked for the password but once the key has been copied you will be able to ssh just perfectly.
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Doing visudo you get nano instead of your favorite text editor?
Mine is vim therefore I issue:
DEBIAN/UBUNTU way
# update-alternatives --config editor
There are 4 alternatives which provide `editor'.
Selection Alternative
-----------------------------------------------
1 /usr/bin/vim.tiny
2 /bin/ed
*+ 3 /bin/nano
4 /usr/bin/vim.basic
Press enter to keep the default[*], or type selection number:
Selecting 4 I’m ready to use my full syntax colors when I edit any file.
OTHER DISTROS
Edit your .bashrc file and add the following:
EDITOR=vim
export EDITOR
Next login you will have your VIM working.
If you want to have it immediately and only for this session just type
# export EDITOR=vim
and press enter.
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I’ve come across multiple ways of doing it but so far the best way is the following (I assume you are on i386 platform and you have access to the net):
1. Download boot.img.gz from Debian website
2. Download the net-install image choosing i386.
3. Plug your USB drive into a Linux PC, open the shell and type
$ dmesg
Last few lines should be like the following:
sd 7:0:0:0: [sdb] Attached SCSI removable disk
sd 8:0:0:0: [sdb] 4030464 512-byte logical blocks: (2.06 GB/1.92 GiB)
sd 8:0:0:0: [sdb] Write Protect is off
Now we know it has been mapped as sdb
4. Use zcat to load the boot.img.gz onto your USB drive
# zcat boot.img.gz > /dev/sdb
CAUTION!!! this will destroy the entire data on the USB drive, make sure you have done the backup.
If you get an error ensure the following:
- You are root (don’t use sudo)
- The USB drive it’s not mounted, if it is umount it before issuing the above command.
5. Now mount the USB drive and copy the net-inst.iso image on it.
All done! Now plug it into the box you want to setup and enjoy the old fashion Debian installer 
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This tip might comes handy when you do a system check and you want to make sure you don’t check the same file twice.
Let’s pretend that our “file1″ is a conf file that needs review. As you can see the output of the command issued below shows that the file was last edited in June.
Today I want to check the file without editing it and make sure next time I won’t check it again:
$ ls -l
total 0
-rw-r--r-- 1 luca luca 290 2009-06-29 16:33 file1
Touch is an excellent tool in this case:
$ touch file1
$ ls -l
total 0
-rw-r--r-- 1 luca luca 0 2009-08-29 19:43 file1
The Modification Time has changed and so has the access time.
If you want to change just the modification time leaving the access time untouched try with the -m option
$ touch -m file1
$ ls -l
total 0
-rw-r--r-- 1 luca luca 0 2009-08-29 19:46 file1
$ stat file1
[..]
Access: 2009-08-29 19:43:45.000000000 +0100
Modify: 2009-08-29 19:46:15.000000000 +0100
Change: 2009-08-29 19:46:15.000000000 +0100
And -a is just for the Access Time.
Another interesting option is -t. It lets you set the time and the date with whatever you like. This is often used to do fishy things
$ touch -t 200701012301 file1
$ stat file1
[..]
Access: 2007-01-01 23:01:00.000000000 +0000
Modify: 2007-01-01 23:01:00.000000000 +0000
Change: 2009-08-29 19:52:26.000000000 +0100
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All broadcasts messages are dropped by the router when it receives on an interface. This specific command is enables the router to convert the broadcast messages distended for a specific destination into unicast. This interface level command needs to be applied on the interface which the broadcast receives from.
R1(config-if)#ip helper-address 10.10.10.10
Also there are other options where you point the address to a vrf etc…
The following broadcasts are forwarded by default…
TIME – Port 37
TACACS – Port 49
DNS – Port 53
BOOTP/DHCP Server – Port 67
BOOTP/DHCP Client – Port 68
TFTP – Port 69
NetBIOS Name Service – Port 137
NetBios Datagram Service – Port 138
Other protocols can be forwarded by using the following Global config commanding…
R1(config)#ip forward-protocol udp ?
Use the ? to see the supported protocols. You may use the following command to remove a specific protocol being forwarded…
R1(config)#no ip forward-protocol udp ?
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