Cheat Sheets

Nice site:

http://packetlife.net/cheatsheets/

for cheatsheets for networkers.

Alternative of WinSCP in Linux

1. Krusader
2. Try secpanel from http://secpanel.net/  or at http://www.pingx.net/secpanel/
3. If you use KDE, Konqueror (the file manager) can be used to access remote servers using the fish protocol. Fish
   (FIles transferred over SHell)is a protocol that uses SSH or RSH to transfer files between computers and to manage
   remote files. Also you can try ’sftp’.
    How: In Konqueror where current directory is listed type:
    fish://{username}@{server-name}/{path-on-remote-server}
    sftp://{username}@{server-name}/{path-on-remote-server}

Ref:
http://winscp.net/forum/viewtopic.php?t=5305
http://boodebr.org/main/node/12

How many times a unacknowledge packet is retransmitted?

• Two types of packets in EIGRP—
unreliable and reliable
Hellos and Acks are unreliable
Updates, queries, and replies are reliable
• Reliable packets require an acknowledgement

If not acknowledged, packets are retransmitted, up to 16 times!

• 16 retransmits must occur AND hold time period must expire before declaring the
neighbor down.
• Retransmissions based on RTO, which is derived from SRTT
• 16 retransmits takes between 50 seconds and80 seconds

TOS Explained in: metric weight [0] k1 k2 k3 k4 k5 EIGRP command

I’d confusion on the significance of TOS field in ‘metric weight tos k1 k2 k3 k4 k5′
eigrp mode command. I googled and compiled this to solve my confusion.

#router eigrp 1

metric weight [0] k1 k2 k3 k4 k5

[0] is TOS. What does it do in EIGRP metric calculation?

TOS is not used in the calculation, it’s Bandwidth, Load, Delay, Relaibility
and MTU, hence K values equal 10100 where only Bandwidth and Delay are used
in the calculation by default. Cisco documentation for EIGRP clearly states that
the “Type of service must always be zero”.

OSPF also supports TOS 0 routes only, which are sometimes referred to as
“single TOS routes”. TOS is neither used for metric calculation there.

Second, this has nothing to do with the fact that packets like VoIP which have
a higher TOS value than the standard traffic are transported with higher priority
- if QoS is configured properly in your network. Supporting different TOS values
in the routing protocols would mean that VoIP traffic and standard traffic could
be sent completely different ways to the same destination.

So the fact that EIGRP and OSPF only support TOS 0 routes simply means that all
traffic to a certain destination has to follow the same route using the same next
hop address. Nevertheless, QoS will take care that VoIP traffic will travel with
higher priority.

The TOS byte in the IPv4 header has had various purposes.8 bits in the IP header
are reserved for the service type. They can be divided into 5 subfields:

The 3 precedence bits have a value from 0 to 7 and are used to indicate the
importance of a datagram. Default is 0 (higher is better).Here binary value
000 to 111 in decimal 0 to 7. Bits 3 4 5 represent the following:
D: requests low delay
T: requests high throughput
R: requests high reliability

A router SHOULD consider the TOS field in a packet’s IP header when deciding
how to forward it.

A router MUST maintain a TOS value for each route in its routing table. Routes
learned through a routing protocol that does not support TOS MUST be assigned
a TOS of zero (the default TOS). [like EIGRP and OSPF ]

Routers use the ToS to choose a destination for the packet.

1. The router locates in its routing table all available routes to the destination.
2. If there are none, the router drops the packet because the destination is unreachable.
3. If one or more of those routes have a TOS that exactly matches the TOS specified in the
packet, the router chooses the route with the best metric.
4. Otherwise, the router repeats the above step, except looking at routes whose TOS is zero.
5. If no route was chosen above, the router drops the packet because the destination is unreachable

Support for TOS in routers may become a MUST in the future,  but is a SHOULD for now until
we get more experience with it and can better judge both its benefits and its costs.

Various people have proposed that TOS should affect other aspects of the forwarding function.
For example:

1. A router could place packets that have the Low Delay bit set ahead of other packets in its
output queues.

2. a router is forced to discard packets, it could try to avoid discarding those which have the
High Reliability bit set.

site: www.google.com and www.sadikhov.com

What is M3UA?

M3UA [ MTP3 user application ]enables SS7 protocol’s user part (ISUP,SCCP,TUP)
to run over IP.SCTP is recommendate to trasmit M3UA.

By making the network introduction complexity and integration problem much shorter,
the time for marketing these new applications will be much faster. SS7 over IP also
solves the throughput limitation that was inherited from the SS7 standards, thus
allowing high-end machines like SMSC, HLR, and so on to be able to support heavy
SS7 traffic needs.

Ref:  http://www.iec.org/online/tutorials/ss7_over/index.asp
http://en.wikipedia.org/wiki/M3UA

InterfaceMapper : Find the interface Configuration for whole network

InterfaceMapper is a script which works on IOS configuration and process it to display port information nicely.
See the attached file below:

HOSTNAME|HOSTIP|INTERFACE|DESCRIPTION|IP ADDRESS|SUBNET ADDRESS
—————|———-|————–|——————|—————-|———————-
NODE-A   |1.1.1.1|Vlan2|*** Management VLAN ***|1.1.1.1|255.255.255.0
NODE-B   |2.2.2.2|Vlan10|***Uplink Switch ***  |2.2.2.2|255.255.255.0
< Output omitted for brevity >

Link to text file of the output:
http://mustafa.golam.googlepages.com/InterfaceMapperOutput.txt

This shell scripts < http://mustafa.golam.googlepages.com/RouterPorts.sh >
finds the current directory of IOS backup files and calls the awk scritps
< http://mustafa.golam.googlepages.com/port_mapper.awk > to process the IOS
configuration and display nicely as above.

You can export the file as “|” seperated file in Excel and further processing.

telnet to multiple Hosts/Routers from linux/unix bash command line

#!/bin/bash

export USERNAME=xxxxx <user-name-to-connect-to-the-node>
export PDW=xxxxxxxx        <password-of-the-user>

cat hosts.txt | while read H

#if the username and password are different for different nodes, the try here to get
# username and password in some variable. Awk/Perl or simple bash string replacement of variable
# H will do that.

do
( echo open $H
sleep 1
echo $USERNAME
sleep 1
echo $PDW
sleep 1
/somedir/some_script.sh 2>&1 > /dev/null
echo exit ) | telnet
done

Ref: http://www.unix.com/shell-programming-scripting/27474-perl-script-telnet.html

CCIE Lab Practice without Terminal Server in Linux

1. Read http://johncurtisccie.blogspot.com/2008/03/dynamips-with-fedora-linux.html    and download telnet.bin to your computer.
2. Make telnet.bin executable in your distro. [try alien/rpm whatever]
3. Use the script bellow to telnet.bin all the running instanses assuming they are running.

#!/bin/bash
(sleep 1) | telnet.bin 127.0.0.1 2200 &
(sleep 1) | telnet.bin 127.0.0.1 2201 &
(sleep 1) | telnet.bin 127.0.0.1 2202 &
(sleep 1) | telnet.bin 127.0.0.1 2203 &
(sleep 1) | telnet.bin 127.0.0.1 2204 &
(sleep 1) | telnet.bin 127.0.0.1 2205 &
(sleep 1) | telnet.bin 127.0.0.1 2206 &
(sleep 1) | telnet.bin 127.0.0.1 2207 &
(sleep 1) | telnet.bin 127.0.0.1 2208 &
(sleep 1) | telnet.bin 127.0.0.1 2209 &
(sleep 1) | telnet.bin 127.0.0.1 2210 &
(sleep 1) | telnet.bin 127.0.0.1 2211 &
(sleep 1) | telnet.bin 127.0.0.1 2212 &
(sleep 1) | telnet.bin 127.0.0.1 2213 &

4. Use ‘fg 1->13′ to foreground the telnet.bin processess, and Ctrl+Shift+6 and fg
key sequence to switch between different instances quickly.

Benefit: you have single window with quick access to all the routers and switches.

Next Hop rechability issue with Cisco/Juniper/Huawei Gears

Next Hop rechability issue with Cisco/Juniper/Huawei Gears:

Similar threads:

http://newsgroups.derkeiler.com/Archive/Comp/comp.dcom.sys.cisco/2008-03/msg00009.html

With reference to BFD:

http://puck.nether.net/pipermail/cisco-nsp/2008-January/046785.html

Do we recall these?

1.         Even before router is configured with static routes, it has a routing table.

2.         Each routed protocol (like IP or IPX) maintains its own routing table.

3.         Before any static (or dynamic) routes exist, a routing table will show entries for only

directly connected networks.

4.         The complete syntax of the “ip route” command is:

ip route [destination network] [mask] [next hop address OR exit interface]

[administrative distance] [permanent]

5.         Directly connected network is Coded with “C” while Static Routes are Coded as “S” in

“show ip route” command’s output.

6.         AD for Directly Connected network is “0″ where as for Static Route it’s “1″.

7.         When the primary route is a static route, the primary interface line protocol must go

down for the floating static route to be used.

Reference:

http://www.cisco.com/en/US/tech/tk801/tk133/technologies_tech_note09186a008009457d.shtml#floating_sequence

Solution:

8.         Enabling next hop rechability information in JUNOS: (RTR)

http://www.juniper.net/techpubs/software/junos/junos92/swconfig-routing/enabling-next-hop-reachability-information.html

Configuring Bidirectional Forwarding Detection in JUNOS:

http://www.juniper.net/techpubs/software/junos/junos73/swconfig73-routing/html/routing-tables-config22.html11.

9.         Configuring BFD Support for Static Routing:

http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_bfd_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1055179

10.        Limitations: IOS, Platfor and Protocol:

For Cisco IOS Release 12.2(33)SRC, and Cisco IOS XE Release 2.1, BFD is supported for static routing.

11.        Use dynamic protocols, they were invented to solve this issue.

How to reset password of a user in ZenOSS?

You can reset zope’s password using
zpasswd.py -u admin -p yourpass inituser
then restart zope with zopectl restart

Also familiar yourself with all the commands
available at : /[.]+/{bin} directories under
zenoss installation directory.

Read more at : http://www.zenoss.com/community/docs/howtos/

and    http://www.zenoss.com/community/docs/faqs/