2013年3月21日星期四

Cisco New EA4500 Dual-band 802.11n Router Review



With its novel cloud-based configuration and app platform, Cisco's EA4500 is an interesting experiment, but the hardware itself fails to excite.

Pros
·                            Simple setup
·                            Compact and stylish design
·                            Easy remote configuration from any browser
·                            Third-party apps can add extra functionality
·                            Good range
·                            Guest network
·                            Dual-radio, three-stream MIMO
Cons
·                            Setup wizard assumes a wireless connection
·                            Limited configuration options when no web connection
·                            Single USB port
·                            Lacklustre maximum throughput

The usability of routers has always left plenty to be desired. With interfaces seemingly designed by engineers on a tight deadline, they frequently assume a high level of technical expertise. There have been a few attempts to introduce more user-friendly graphical interfaces, but none have gone quite as far as Cisco's latest offering.

Cisco Connect Cloud makes its debut in the new EA4500 dual-band 802.11n router, and comprises a graphical user interface with a cloud-based component to give remote access features. The novelty is that Cisco has made an SDK available to third-party app developers via the Linksys Developer Community, allowing the creation of apps that integrate with what Cisco is calling its 'Smart Wi-Fi App Enabled Routers'. Apps to control devices like NAS appliances are nothing new, but these are usually in-house products.

At launch, six commercial apps were announced for iOS and/or Android devices — a full list is available on Cisco's website. These include the web filtering and blocking tools Netproofer and Block the Bad Stuff, streaming media players Hipplay and Twonky Video, Device Monitoring and the Gemini IP camera monitoring utility. Not all of these apps were available at the time of writing, but there is a free Cisco Connect Cloud app for iOS and Android that allows access to a few router settings such as guest access and parental controls.

Cisco's dual-band 802.11n EA4500 has 4 Gigabit Ethernet ports and an RJ-45 WAN port, plus a USB 2.0 for storage or printer sharing.

The router itself is nothing out of the ordinary, sharing an identical chassis and very similar innards to the existing E4200 v2 model. It has three-stream MIMO (450Mbps) capability on both 2.4GHz and 5GHz radios, courtesy of twin Marvell 88W8366/88W8063 transceivers. The six internal antennas are a folded metal design arranged around three sides, and the sleek grey and silver case dispenses with any status lights apart from those on the four Gigabit Ethernet LAN and single WAN ports (there is no ADSL version). There's also a white-illuminated Cisco logo showing power status.

Inside the EA4500 you'll find two Marvell transceivers (2.4GHz and 5GHz), plus six internal antennas.

A USB 2.0 port completes the I/O features; this can be used for sharing either storage or printers, but 3G dongles are not supported. For printer and multifunction device sharing, a simple USB-over-IP utility is provided for client PCs.

Setup is via a CD-based wizard, and is a simple process apart from the fact that it's intended to be used over a wireless connection. We tried it over wired Ethernet and (after upgrading the firmware to the latest version) it worked, although the instructions in the wizard make no reference to wired connections. The wizard optionally allows the SSID and encryption keys to be changed, along with the router admin password and network name.

Once you've created and logged into a Cisco Connect Cloud account, your router and its settings are accessible from anyhwere with a browser and an internet connection.

The admin interface is accessed by logging in at www.ciscoconnectcloud.com and creating a free account. The full service requires a web connection — if this is down, you can login locally using the router admin password, but only basic WAN and LAN settings can be modified. If the internet is OK, the router is associated with the Cisco Connect Cloud account, and all settings are then accessible via the local LAN or remotely from any browser. It's a somewhat clumsy system — reverting to a standard fully-featured text-based menu in the absence of a web connection might have made more sense. (Cisco has responded to early customer complaints on this issue, and does allow a firmware downgrade to a traditional interface, bypassing Cisco Cloud Connect altogether).

The Connect Cloud interface is more user-friendly than your average router's web-based management console.

The interface is fairly intuitive, if a little slow and unresponsive, with configurable widgets showing the status of various settings arranged to the right of a list of categories. The top six categories are labelled 'apps', with router settings below these. It seems an odd distinction, but any setting in the app section is only accessible when there's a working web connection. These built-in apps provide parental controls, USB storage settings, LAN client management, Wi-Fi guest access, media prioritisation (QoS) and an internet speed test applet. Third-party apps do not appear on this list, however.

There are plenty of advanced settings tucked away in the various LAN and WAN settings menus, such as port forwarding, DMZ, MAC filters and so on, so experienced users need not despair of too much dumbing down. The DLNA media server and file sharing (via SMB or FTP, but not HTTP) are configured in the USB Storage app, but confusingly printers are added via the Device List. All remote access features can be disabled if needed without affecting local configuration options, but third-party apps may be affected as these hook into the cloud-based service, not the local network.

Performance was a very mixed bag. Using our standard setup of a notebook with an Intel Ultimate Wi-Fi Link 5300 and Passmark Performance Test 7, at 1m range on the 2.4GHz band (auto 20/40MHz setting) it delivered a distinctly average 44Mbps. However, at 25m it showed impressive stamina, maintaining around 26Mbps with no trouble. At 5GHz (with 40MHz-only channels configured) it improved to 57Mbps at 1m but dropped marginally to 23Mbps at 25m. These are good long-range results, but they don't really compensate for the unexceptional close-range performance.

Although we applaud the attempt to simplify configuration, other router manufacturers are already heading down similar paths. The app platform may be unique, but its success depends very much on enticing good developers to produce appealing apps. As a showcase for this new platform, the EA4500 is fine, with good usability and a solid, if unexciting, feature set. But its wireless performance is disappointing, and some fine tuning of the setup and configuration procedures is still needed.

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2013年3月19日星期二

Cisco Routing Study Guide: Configuring OSPF in a Single Area



OSPF stands for Open Shortest Path First and it represents a routing protocol belonging to the group of link-state routing protocols.

OSPF routing protocol is classified among the best dynamic protocols that exist in networks today. It is also considered to be a sophisticated routing protocol that aims to maintain loop-free and accurate routing tables.

Today, we’ll go over the necessary commands that are needed to enable the OSPF routing protocol, define OSPF networks, configure advanced options, and more. We’ll also look at how and why OSPF is used.

Let’s get started by taking a look at some
Unlike distance vector protocols, link-state routing protocols, and specifically OSPF, hold the following key points:
  • Information about its neighbors (local connectivity) is sent to the entire network using multicasting
  • The entire routing table is transmitted once every 30 minutes
  • Link-state updates (LSAs) are transmitted when there is a change in the state of the links
  • HELLO messages are used to maintain adjacent neighbors
  • Is a classless routing protocol which uses VLSM and both manual and automatic summarization
  • Uses COST as a metric which CISCO defines as the inverse of the bandwidth
  • AREA terminology is created to provide a hierarchical structure and limit the multicast LSAs within routers of the same area — the default or otherwise core area is area 0 and all other areas connect directly to it

Based on OSPF LSAs, each router constructs a topology table which contains every connection link within the network. Then, the Dijkstra algorithm runs over the topology table to find the shortest path to every other router, and hence creates the routing table.

This algorithm, which is also known as the SPF algorithm, runs on every OSPF enabled router on the network, and routers within a particular area all have the same topology tree of the specific area.

Enabling the OSPF Routing Protocol
The following command is needed in order to enable OSPF routing protocol on the router:
  • Router(config)#router ospf process-number

The process-number is nothing more than a number local to the router. It’s only used to distinguish processes within a router and can be given an arbitrary value. This value does not have to be the same on every router within the area. However, it is always good practice to keep this number the same for better administration.

Defining OSPF Networks
Enabling OSPF is not enough to activate it. The OSPF process needs to know the networks that are going to be advertised (i.e. the interfaces on which OSPF will run)and the area they reside in. Therefore the following command is needed to make OSPF operational:
  • Router(config-router)#network address wildcard-mask area area-number

The address can be the network address, subnet, or the address of a specific interface.

The network command is used to identify the interfaces on the router that are going to participate in the OSPF process. Adjacencies will be created with these interfaces and LSAs will be received and transmitted on these interfaces.

Therefore the wildcard-mask parameter needs to be defined for accurately identifying the necessary interfaces.

The wildcard-mask consists of 4 groups of 8-bits each. Each 0 bit indicates a “must” and each 1 bit indicates an “any”. This will become clearer in the next section on Defining OSPF Networks Examples.

The area-number specifies the area to be associated with the specific address and consequently the interfaces to be grouped within that area.

By default, area 0 is used; if more than one area is to be created in a network, area 0 is the first one that needs to be defined.

Defining OSPF Networks Examples
The schematic diagram below illustrates how a single command is able to cover all router interfaces and also how individual interfaces can be specified.


In the diagram above, RouterA has 3 interfaces, one in the 192.168.7.0 subnet, one in the 192.168.8.0 subnet and the other in the 172.16.1.0. The following command configures all interfaces to participate in OSPF area 0:
  • Router(config-router)#network 0.0.0.0 255.255.255.255 area 0

The following command will force only interfaces addressed from 192.168.0.0 to participate in OSPF:
  • Router(config-router)#network 192.168.0.0 0.0.255.255 area 0

The following command specifically forces the serial interface to participate in OSPF area 0:
  • Router(config-router)#network 172.16.1.1 0.0.0.0 area 0

Configuring Advanced Options
A few advanced options can be useful in administrating OSPF, though they are not necessary for OSPFs normal operation. These options include:
  • Configuring a loopback interface
  • Specifying the router ID (RID)
  • Manipulating the cost command
  • Changing the routers priority

Configuring a Loopback Interface
The source of Link-state Advertisements in a given area is identified by the RID. This ID has the form of an IP address and can be automatically or manually defined.

Automatic selection of RID
If no manual RID is specified, then the RID is taken from the highest IP address assigned to a loopback interface. If no loopback interface is defined, then the highest IP address of an active interface is chosen as the RID.

It is wise to configure a loopback interface on the router because this kind of interface is a virtual one that can never go down; hence the RID will never have to change. The following commands define and configure a loopback interface:
  • Router(config)#interface loopback interface-number
  • Router(config-if)#ip address ip-address subnet-mask

Manual Configuration of RID
This is the preferred method of defining the RID. Any unique IP address can be defined as RID and it never changes even if the interface that the router is using for the RID goes down.

Even when a manual configuration change of the RID is performed, this does not take effect until the next router reload or OSPF routing restart.

The following commands show how to manually configure the RID. The clear ip ospf processcommand is used to activate the RID on a router that is already running OSPF:
  • Router(config)#router ospf process-number
  • Router(config-router)#router-id ip-address
  • Router#clear ip ospf process

Configuring the Cost of an Interface
As already mentioned, the OSPF process assigns cost values to interfaces based on the inverse of the bandwidth parameter assigned to the interface with the bandwidth command.

For calculating the SPF to a given destination, the router takes into consideration the costs of the links along various paths. The path with the lower cost is selected as the shortest path.

To force the router to pick up a certain path, manual setting of the cost on a link along the path can be achieved using the following command:
  • Router(config-if)#ip ospf cost cost

Setting Priority for the Selection of the Designated Router
In multi-access networks the router with the highest priority value is chosen as the DR which acts as the central point of LSAs exchange.

The priority command is assigned on an interface. Default priority for an OSPF interface is 1. The range is from 0 to 255. 0 means that the interface does not involve in the DR election.
The following command configures a priority value on an interface.
  • Router(config)#interface interface-number
  • Router(config-if)#ip ospf priority priority-value

Why Use OSPF?
As I mentioned at the beginning, OSPF routing protocol is classified among the best dynamic protocols existing in networks today. It has all the necessary features of an interior gateway routing protocol:
  • Scalability
  • Adaptability to topology changes
  • Topology awareness within its operation area

OSPF uses multicasting so that each router informs all other routers in the area of its neighbors and costs. This information allows each router to build a complete topological tree consisting of routers and omnidirectional links connecting them together. Each of these links carries a cost value.

SPF algorithm runs over this topology tree and computes the shortest path from every router to every other router in the area. The results from SPF algorithm construct the router’s routing table.

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2013年3月15日星期五

DHCP Snooping Option 82 Configuration Examples



This document describes the typical application environment and configuration examples for DHCP snooping Option 82.

Acronyms:
Acronym
Full spelling
DHCP
Dynamic Host Configuration Protocol
DNS
Domain Name System
giaddr
Gateway IP address
WINS
Windows Internet Naming Service

1 Feature Overview
Option 82 is the relay agent option which records the location information of the DHCP client. When a DHCP snooping device receives a client’s request, it adds Option 82 to the request message and sends it to the server. Then, the DHCP server can assign a proper IP address and other parameters for the client. The administrator can also use Option 82 to implement security control and accounting.

2 Application Scenarios


Figure 1 Option 82 application
Typically, a DHCP server assigns an IP address based on the giaddr filed of the client’s request or the IP address of the interface that received the client’s request. In Figure 1, the DHCP server assign IP addresses to Host A and Host B from the network segment where the clients belong.
Traditionally, the DHCP server cannot assign to Host A an IP address that is in a different network segment from the IP address assigned to Host B. However, this can be achieved through Option 82, with which, the DHCP server can assign IP addresses based on the DHCP snooping interface connected to the clients and the giaddr filed in DHCP requests.

A client’s ID can be recognized by Option 82. Therefore, the DHCP server can assign a unique IP address to each client, to further implement QoS, security and accounting management.

3 Configuration Guidelines
u      The DHCP snooping Option 82 function can take effect only after you enable DHCP snooping.
u      DHCP snooping does not support link aggregation. If a Layer 2 Ethernet interface is added into an aggregation group, DHCP snooping configuration on it will not take effect. When the interface is removed from the group, DHCP snooping can take effect.
u      The DHCP snooping enabled device does not work if it resides between a DHCP relay agent and DHCP server, and it can work when it resides between a DHCP client and relay agent or between a DHCP client and server.
u      You are recommended to enable the DHCP snooping Option 82 function on the DHCP snooping device closest to the DHCP client for locating the client accurately.
u      The DHCP snooping enabled device cannot act as a DHCP server or DHCP relay agent.
u      You are not recommended to enable the DHCP client, BOOTP client, and DHCP snooping on the same device. Otherwise, DHCP snooping entries may fail to be generated, or the BOOTP client/DHCP client may fail to obtain an IP address.

4 Configuration Examples
4.1 Network Requirements
The work area of an enterprise is divided into three groups, group 1, group 2, and group 3, which are located in three rooms. A DHCP server is deployed to assign IP addresses of different segments to the three groups.
It is required that:
*        The DHCP server assigns IP addresses on the network segment 192.168.10.0/24 to devices in the work area. The lease time is 12 hours, and the DNS and WINS server addresses are 192.168.100.2 and 192.168.100.3 respectively.
*        Group 1, group 2 and group 3 are connected to the DHCP snooping device through Ethernet1/1, Ethernet1/2 and Ethernet1/3 respectively to communicate with the DHCP server.
*        The DHCP server assigns IP addresses ranging from 192.168.10.2 to 192.168.10.25 to clients in group 1, assigns IP addresses ranging from 192.168.10.100 to 192.168.10.150 to clients in group 2, and assigns IP addresses ranging from 192.168.10.151 to 192.168.10.200 to clients in group 3.

Figure 2 Network diagram for DHCP snooping
4.2 Configuration Considerations
ü        Enable Option 82 support on the DHCP snooping device.
ü        Configure the Option 82 sub-option, so that the clients in different groups can send packets carrying different Option 82 information. To do so, you can manually specify the circuit ID sub-option.
ü        Configure IP address assignment policy on the DHCP server, so that the DHCP server can assign proper IP addresses to the DHCP clients according to Option 82.

4.3 Software Version Used
This example is configured and verified on Comware V500R002B42D001.

4.4 Configuration Procedures
Note:The following configurations are made on devices that are using default settings and verified in a lab environment. When using the following configurations on your devices in a live network, make sure they do not conflict with your current configurations to prevent potential negative impact on your network.

4.4.1 Configuration on the DHCP Snooping Device
I. Configuration steps
# Enable DHCP snooping.
<Switch> system-view
[Switch] dhcp-snooping
# Configure Ethernet 1/4 as a DHCP snooping trusted port.
[Switch] interface ethernet 1/4
[Switch-Ethernet1/4] dhcp-snooping trust
[Switch-Ethernet1/4] quit
# Enable Ethernet 1/1 to support Option 82.
[Switch] interface ethernet 1/1
[Switch-Ethernet1/1] dhcp-snooping information enable
# Pad the Option 82 circuit ID sub-option with group 1.
[Switch-Ethernet1/1] dhcp-snooping information circuit-id string group1
[Switch-Ethernet1/1] quit
# Enable Ethernet 1/2 to support Option 82.
[Switch] interface ethernet 1/2
[Switch-Ethernet1/2] dhcp-snooping information enable
# Pad the Option 82 circuit ID sub-option with group 2.
[Switch-Ethernet1/2] dhcp-snooping information circuit-id string group2
[Switch-Ethernet1/2] quit
# Enable Ethernet 1/3 to support Option 82.
[Switch] interface ethernet 1/3
[Switch-Ethernet1/3] dhcp-snooping information enable
[Switch-Ethernet1/3] quit
# Pad the Option 82 circuit ID sub-option with group 3.
[Switch-Ethernet1/3] dhcp-snooping information circuit-id string group3
[Switch-Ethernet1/3] quit

II. Configuration file
<Switch> display current-configuration
#
interface Ethernet1/1
 port link-mode bridge
 dhcp-snooping information enable
 dhcp-snooping information circuit-id string group1
interface Ethernet1/2
 port link-mode bridge
 dhcp-snooping information enable
 dhcp-snooping information circuit-id string group2
interface Ethernet1/3
 port link-mode bridge
 dhcp-snooping information enable
 dhcp-snooping information circuit-id string group3
#
interface Ethernet1/4
 port link-mode bridge
 dhcp-snooping trust
#

4.4.2 Configuration on the DHCP Server
I. Configuration steps
You can use the following two methods to configure Option 82:
1.        User-defined method: Manually specify the content of Option 82.
2.        Non-user-defined method: Pad Option 82 in the default normal or verbose format.

For the second method, the circuit ID sub-option format is as shown in Figure 3 .

Figure 3 Circuit ID sub-option format
For example, for clients connected to Ethernet 1/1, the circuit ID sub-option is padded with group 1. The circuit ID sub-option in DHCP packets should contain the following information: 0x010667726F757031, in which 0106 refers to the number and length of the circuit ID sub-option, and 67726F757031 refers to the hexadecimal value of the character string group 1.

In this example, IP addresses are assigned according to the group number; therefore, the DHCP server only needs to assign IP addresses based on the group number padded in the circuit ID sub-option.

Note:The DHCP server is configured on a Cisco Catalyst 3745 switch with software version IOS 12.3(11)T2. To configure a device of another type or version as the DHCP server, refer to the related user manual.

# Configure the server interface IP address as 192.168.10.1/24.
Server> enable
Server# configure terminal
Server(config)# interface fastethernet 0/0
Server(config-if)# ip address 192.168.10.1 255.255.255.0
Server(config-if)# exit
# Enable DHCP server, and configure the DHCP server to assign IP addresses based on Option 82.
Server(config)# service dhcp
Server(config)# ipdhcp use class
# Create a DHCP class for clients in group 1, and specify the corresponding circuit ID sub-option for matching. For the content not to be matched, enter the wildcard ”*”.
Server(config)# ipdhcp class group1
Server(dhcp-class)# relay agent information
Server(dhcp-class-relayinfo)# relay-information hex 010667726F757031*
Server(dhcp-class-relayinfo)# exit
# Create a DHCP class for clients in group 2, and specify the corresponding circuit ID sub-option for matching.
Server(config)# ipdhcp class group2
Server(dhcp-class)# relay agent information
Server(dhcp-class-relayinfo)# relay-information hex 010667726F757032*
Server(dhcp-class-relayinfo)# exit
# Create a DHCP class for clients in group 3 and specify the corresponding circuit ID sub-option for matching.
Server(config)# ipdhcp class group3
Server(dhcp-class)# relay agent information
Server(dhcp-class-relayinfo)# relay-information hex 010667726F757033*
Server(dhcp-class-relayinfo)# exit
# Create a DHCP address pool named office, and specify the lease time, gateway address, DNS server address, and WINS server address for clients.
Server(config)# ipdhcp pool office
Server(dhcp-config)# network 192.168.10.0
Server(dhcp-config)# lease 0 12
Server(dhcp-config)# default-router 192.168.10.1
Server(dhcp-config)# dns-server 192.168.100.2
Server(dhcp-config)# netbios-name-server 192.168.100.3
# Specify address ranges for the three DHCP classes respectively.
Server(dhcp-config)# class group1
Server(dhcp-pool-class)# address range 192.168.10.2 192.168.10.25
Server(dhcp-pool-class)# class group2
Server(dhcp-pool-class)# address range 192.168.10.100 192.168.10.150
Server(dhcp-pool-class)# class group3
Server(dhcp-pool-class)# address range 192.168.10.151 192.168.10.200

4.4.3 Verification
After completing the above configurations, the DHCP server can automatically assign IP addresses of the specified range, gateway address, DNS server address, and WINS server address for clients of each group in the work area.

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