My Netwok Dictionary

Today I needed to get interested in how memory works at the IOS, so here is a quick article about it with the information I could find here and there, you might be interested.Especially the IOS commands to check the memory status of your router.

Like any OS, IOS must implement a number of basic principles:

* Process Management
* Memory Management
* Device Management

We’ll look specifically at the system memory management. Recent work with OS protected memory.A process x can not access the memory of a process y (Shared Memory, Message Queues, Pipes, Network Connections, …). For the process x process dialogue with it, they will have to use other methods (Shared Memory, Message Queues, Pipes, Network Connections, …). These methods secure processes between them, but nevertheless they work slow. The IOS does not support shared memory, all processes have access to the memory without restrictions.A process is therefore free to interact with one another in writing in the memory of the latter (Buffer Overflow = Crash).There is however a notion of memory R / W and R / W

IOS works with memory pools, the Pool Manager who is responsible.Here, a pool reserved for the procesand a pool reserved for I / O:

Router # show memory
 Head Total (b) Used (b) Free (b) Lowest (b) Largest (b)
 Processor
 653B8C20 155481056 86243592 69237464 68168948 67670028
 I/O
 EE800000 25165824 5269012 19896812 19819968 19871932

Head: beginning the pool
Total: pool size in bytes
Used: current use of the pool in bytes
Free : current free memory pool in bytes
Lowest :free memory historically the lowest in bytes
Largest :The largest contiguous block of free memory

Region Manager : These same pools belong to regions of memory managed by the Region Manager:

Router # show region

Region Manager:
Start End Size (b) Class Media Name
0×0E800000 0×0FFFFFFF iomem 25165824 R / W iomem: (iomem)
0×60000000 243269632 0×6E7FFFFF Room R / W Hand
0×6000F000 0×632FFFFF iText 53415936 R / O main: text
0×63300000 28310784 0×64DFFCFF iData R / W main: data
0×64DFFD00 0×653B8C1F IBSS 6000416 R / W main: bss
0×653B8C20 0×6E7FFFFF 155 481 056 Room R / W main: heap
0×80000000 243269632 0×8E7FFFFF Room R / W main: (main_k0)
0xA0000000 0xAE7FFFFF 243 269 632 Room R / W main: (main_k1)
0xEE800000 0xEFFFFFFF iomem 25165824 R / W iomem

The Processor memory pool is within the area hand heap. This region is part of the region starting in hand 0 × 60000000 and ends at 0 × 6E7FFFFF. The memory pool I / O is the region of iomem 0xEE800000 to 0xEFFFFFFF.
Read the rest of this entry »

Authentication

Here’s how to configure authentication keys for each router participating in the EIGRP routing process:

R1 # conf t
R1(config)# key chain EIGRP-KEYS
R1(config-keychain)# key 1
R1 (config-keychain-key) # key-string cisco

A2 # conf t
R2 (config) # key chain EIGRP-KEYS
R2 (config-keychain) key # 1
R2 (config-keychain-key) # key-string cisco

Key verification

R1 # show key chain
Key-chain EIGRP-KEYS:
key 1 - text “cisco”
accept lifetime (always valid) - (always valid) [valid now]
send lifetime (always valid) - (always valid) [valid now]

Now that our keys are configured in the router, you must apply to each interface on which you want to authenticate.

Read the rest of this entry »

The configuration and management of a Cisco PIX have logic similar to that of the IOS on the router and the same commands tend, with new releases to look alike.

Especially with the release 6.x, were introduced to the IOS commands common but has been maintained compatibility with older equivalent.

As in any multiuser OS, there are regular and privileged users (enabled). It becomes the root of a Pix with:
Pix> enable
Pix# The prompt changes from> to #
From here you enter configuration mode:
configure terminal
You save the configuration in memory resident (NVRAM, FLASH…) with:
write memory
It displays the current configuration:
write terminal or show running-config
You can view the log messages (to be activated configuration may remain in a local buffer (occupying memory), or logged on syslog remote server) with:
show logging Read the rest of this entry »

Frame Relay operates at the Layer 2 technology and is an NBMA(Non Broadcast Multiple Access).

DTE and DCE

Router DTE, DCE is the FR-switch at the provider.

Local Management Interface LMI

• runs between DTE and DCE
• Allocation of the DLCI DTE possible
• Keepalives
• LMI types: Cisco, ANSI, Q933a
• Auto Sensing from IOS 11.2

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With the Address Resolution Protocol (ARP) can determine IP hosts MAC address to an IP address. This mapping is stored in the ARP cache. An attacker can try using falsified ARP frames to manipulate these Zuordnugn. He may be either a man-the-middle attack in conduct or communication in the network interfere. This type of attack, known as ARP spoofing and ARP poisoning. Read the rest of this entry »

Security was one of the first features for securing network ports. Access to the network via this address controlled. The MAC can access port to specific MAC addresses or a number of addresses to be limited.

In violation of a defined traffic rules can be filtered (violation protect or restrict) or the interface will be disabled (shutdown violation). Read the rest of this entry »

Definition of service quality

The term QoS (an acronym for “Quality of Service”) means the ability to provide service (such as a communication medium) which meets requirements of response time and bandwidth.

Applied to packet switching networks (based networks using routers) for QoS is the ability to be able to guarantee an acceptable level of packet loss, defined by contract, for a given use (VoIP, video conferencing, etc…).

Indeed, unlike circuit-switched networks, such as switched telephone networks, where a communication circuit is dedicated for the duration of the communication, it is impossible to predict Internet path taken by individual packets. Read the rest of this entry »

Introduction to Netstat

Netstat is a tool to determine the TCP connections are active on the machine where the command is enabled and thus list all the ports TCP and UDP open on the computer.

The command “netstat” also provides statistics on a number of protocols (Ethernet, IPv4, TCP, UDP, ICMP and IPv6). Read the rest of this entry »

“Ping” (short for Packet Internet Groper) is without doubt one of the tools of network administration best known. Yet this is one of the most simple since it allows, through the sending packets to verify if a remote machine responds and, by extension, it is accessible via the network.

The ping tool allows to diagnose network connectivity with a command like:

ping name.of.machine

name.of.machine represents the IP address of the machine or its name. It is usually best at first to test with the IP address of the machine. Read the rest of this entry »

Introduction to Traceroute

Traceroute is a tool for diagnosing networks, present on most operating systems, to determine the path followed by a package. The traceroute command allows to draw a map of the routers between a source machine and target machine. The traceroute command differs between operating systems.

Under the systems UNIX / Linux , the traceroute command is as follows:
traceroute name.of.machine

Under the systems Windows , the traceroute command is as follows:
tracert name.of.machine Read the rest of this entry »