Learning IOS and JUNOS

精實新聞 2010-03-17 19:31:06 記者 方巧文 報導 WiMAX 網路電話VOIP (Voice over Internet Protocol)戰火即將在今年下半年展開！ 4G WiMAX由於擁有比現有 3G 、 3.5G 更大的頻寬，業者的服務多強調快速上網。不過，除了行動以及藉由家用路由器將上網範圍擴至室內，WiMAX業者也已計畫推出低價的網路語音電話服務，使WiMAX的業務更為健全，進一步搶食既有 3G 電信業者的市場。 南區與北區的WiMAX業者 大同 電信與全球一動，已不約而同宣布可望在今年下半年推出VOIP服務。其中， 大同 電信將與 正文 (4906)轉投資持股25.32%的普羅通信的Free PP 合作，聚焦在純 固網 的VOIP服務。 而全球一動總經理蔡木源則大聲宣佈，VOIP將是公司今年的重點項目，預計今年下半年將會開始佈建並提供服務。全球一動與 大同 電信不同的地方，在於全球一動除了純 固網 的VOIP外，公司還會推出需要訊號覆蓋率較好的行動VOIP。 VOIP約略可分為2種，一種是採純 固網 的方式，例如skype，另一種則是行動式的VOIP，即是在外用 手機 進行語音通話。由於行動VOIP需要較好的訊號覆蓋率，且區域型的WiMAX營運商還須以已有漫遊規範為前提才能提供較完整的全區性服務，因此目前即使是在國外，也還沒有業者正式推出可通行全國的行動WiMAX語音VOIP服務。 大同 電信表示，公司之前在M-Taiwan計畫時，已有推出 固網 VOIP服務，今年下半年則會讓該服務正式商轉，預計將搭配indoor  CPE 推出相關方案；搭配硬體則將包括由 精英 (2331)製造、可將WiMAX訊號轉換成 WiFI 的可攜式路由器(暱稱方塊酥)。 至於行動VOIP方面， 大同 電信認為，若是在訊號覆蓋率還不夠完善、無法與既有 2G 、 3G 匹敵的狀況下就推出該服務，可能反而會有負面效果。不過， 大同 電信對於全球一動擬推出行動VOIP一事仍表樂觀其成。目前WiMAX業者多已拿到由主管機關分配的電話號碼，如 大同 是09006。 在全球一動方面，目前 宏達電 (2498)與採 聯發科 (2454)解決方案的 手機 都已通過測試。惟目前因WiMAX 手機 單價仍高，一支採購價高達2萬元，蔡木源認為， 手機 採購價要降到1.5...

Beginning April 1, 2010, Cisco will allow Cisco 360 Learning Program students who attend a Cisco CCIE® Routing and Switching or CCIE Voice workshop to request a waiver and skip the  Core Knowledge Section  of the CCIE lab exam.  All waiver requests must be approved by the workshop instructor.  No end date for the Core Knowledge Waiver has been announced, but Cisco will provide at least 60 days’ notice before discontinuing the waiver. During a Cisco 360 Learning Program workshop, students complete a series of performance assessments that demonstrate their understanding of the CCIE material and serve the same purpose as the Core Knowledge section of the exam.  Therefore, Cisco 360 Learning Program students who use the waiver will not be required to type out answers to the Core Knowledge questions and will be allowed to move immediately to the next section of the lab exam. To qualify for the waiver, workshop students should contact their instructor 45 days in ad...

The ip wccp redirect exclude in command should be used on interfaces facing WAAS devices when outbound redirection is configured on other interfaces on the device.  Let's say you have a simple configuration where the router has three interfaces - one LAN facing, one WAN facing, and one used for the WAAS device: ! interface FastEthernet0/0   description ** LAN Interface **   ip address 10.10.10.1 255.255.255.0   duplex auto   speed auto ! interface FastEthernet0/1   description ** WAAS Interface **   ip address 11.11.11.1 255.255.255.248   duplex auto   speed auto !         interface FastEthernet1/0   description ** WAN Interface **   ip address 10.88.81.99 255.255.255.248   duplex auto   speed auto ! You have two choices for how to apply WCCP here: Configure inbound redirection on the LAN (FastEthernet0/0) and WAN (FastEthernet1/0) interfaces. C...

Built on the growing demand for dedicated professionals who can manage, maintain and troubleshoot complex service provider IP NGN core network infrastructures, Cisco is introducing a new Service Provider (SP) Operations track. This new track is focused on developing associate, professional and expert-level capabilities to operate large, complex SP networks. These new, first of their kind certifications are designed specifically for Cisco Service Provider Customers, Partners and Cisco Networking Engineers. Over the coming months Cisco will release new CCIE, CCNP, and CCNA SP Operations courses and exams. In addition, the written exam topics for the CCIE SP Operations certification are now available on the Cisco Learning Network. The CCIE SP Operations written exam is scheduled for release in the second quarter of 2010. CCIE SP Operations Certification The Cisco CCIE SP Operations certification assesses and validates core IP NGN service provider operations expertise....

Cisco's Plan for Service Providers in the Mobile Internet Age As mobile networks feel the strain, Cisco's Pankaj Patel says the company's newly fortified mobile Internet portfolio can help service providers prepare for the future Photo Pankaj Patel, Senior Vice President and General Manager of Cisco's Service Provider Business Related Information Press Release Cisco Unveils the Cisco ASR 5000 Blog The Mobile Internet is Changing Everything! February 9, 2010 Weeks after its recently completed acquisition of Starent Networks, Cisco Systems is holding its first show-and-tell, revealing why the mobile infrastructure supplier was a must-have item last Christmas. At Mobile World Congress in Barcelona, Spain this month, Cisco will unveil the first product to come from the acquisition – a mobile multimedia platform now branded the Cisco ASR 5000 , which Cisco says will play an increasingly key role for service providers as mobile data traffic mushrooms in the...

When you configure PortFast on an access or trunk port, you assure that switch it should not expect a switch on this path. With this assurance, the switch can pass right through forward delay and go directly to forwarding when it gains link. By default, PortFast does not disable STP on the port, but by skipping the listening and learning stats you do increase the probability of creating a loop if a switchin connected. To protect against this situation, you can enable BPDU guard or BPDU filter globally for PortFast port. BPDU guard will error-disable the port if a BPDU is recevied. Switch(config)# spanning-tree portfast bpduguard When the BPDU filter is enabled globally, it causes PortFast ports to stop sending BPDUs. If a BPDU is recevied, the PortFast feature is disabled for that port and normal STP operation resumes. Switch(config)# spanning-tree portfast bpdufilter

Cisco Announces New Service Provider Operations Track Built on the growing demand for dedicated professionals who can manage, maintain and troubleshoot complex service provider IP NGN core network infrastructures, Cisco is introducing a new Service Provider (SP) Operations track. This new track is focused on developing associate, professional and expert-level capabilities to operate large, complex SP networks. These new, first of their kind certifications are designed specifically for Cisco Service Provider Customers, Partners and Cisco Networking Engineers. Over the coming months Cisco will release new CCIE, CCNP, and CCNA SP Operations courses and exams. In addition, the written exam topics for the CCIE SP Operations certification are now available on the Cisco Learning Network. The CCIE SP Operations written exam is scheduled for release in the second quarter of 2010. CCIE SP Operations Certification The  Cisco CCIE SP Operations  certification assesses and validates...

Frame Relay Dual-FIFO On the low-end router non-distributed platforms (Cisco 7200 and lower), Frame Relay employs a dual-FIFO queuing technique that automatically is invoked at the interface level when FRF.12 is configured. FRF.12 depends on Frame Relay traffic shaping (FRTS) or class-based FRTS being enabled. In a Frame Relay environment, the Tx-ring does not directly provide back pressure to the Layer 3 queuing algorithm. Instead, when the Tx-ring is full, it provides back pressure to the shaper (FRTS or CB-FRTS), which, in turn, signals the Layer 3 queuing system (LLQ) to engage. Because the FRTS mechanism does not take into account Frame Relay headers and cyclic redundancy checks (CRCs) in its calculations, it generally is recommended that you shape to 95 percent of CIR on Frame Relay circuits up to T1/E1 speeds. This, in turn, engages the LLQ algorithm slightly earlier and improves performance for real-time traffic. Traffic from each PQ for each DLCI is funneled into the hi...

在Cisco QoS 2.3課程中的ECN(Explicit Congestion Notification)的章節中第一次談到了ECN-Echo(ECE)，透過ECE(注意，這個欄位不在ToS中，而是在TCP header中的flag之一)可以通知對方放慢傳送的速度。當另一方收到ECE時，會減少它的congestion windows來放慢傳輸速率。然後在第一個封包中設置TCP header flag(CWR, Congestion Window Reduced)，用來通知原先發送ECE的那一方已經減少windows size並且放慢了傳輸速率． TCP 中的 ECN 支援 當路由器將 IP 封包的 ECN 欄位設定為 11 時，接收端 (而不是傳送端) 就會接到路徑中擁塞的通知。ECN 使用 TCP 標頭向傳送端指出網路正遇到擁塞狀況，同時向接收端指出傳送端已經從接收端接到擁塞指標，並且降低傳輸速率。 TCP 中的 ECN 支援使用 TCP 標頭中的兩個未使用位元 (先前定義為保留)。為 ECN 支援定義的兩個新旗標如下所示： • ECE  ECN-Echo (ECE) 旗標是用來指出，在 TCP 三方信號交換程序期間，TCP 對等體具備 ECN 功能，並指出 ECN 欄位在 IP 標頭中設定為 11 的連線上接到 TCP 區段。如需有關 TCP 三方信號交換程序的資訊，請參閱 RFC 793。 • CWR  Congestion Window Reduced (CWR) 旗標是由傳送主機設定，指出已接到設定 ECE 旗標的 TCP 區段。擁塞視窗是由 TCP 維護的內部變數，可管理傳送視窗的大小。 [圖 2] 顯示 TCP 標頭中 ECE 和 CWR 旗標相對於其它旗標的位置。如需有關 TCP 標頭中其它旗標的資訊，請參閱 RFC 793。 圖 2：TCP 標頭中的 ECE 和 CWR 旗標 觀看完整大小的影像 當兩個具備 ECN 功能的 TCP 對等體建立 TCP 連線時，它們交換 Synchronize (SYN)、SYN-Acknowledgement (SYN-ACK) 和 ACK 區段。SYN 區段已經針對具備 ECN 功能的 TCP 對等體同時設定 ECE 和 CWR 旗標；但是 SYN-ACK 區段則是設定...

Introduction The Context-Based Access Control (CBAC) feature of the Cisco IOS® Firewall Feature Set actively inspects the activity behind a firewall. CBAC specifies what traffic needs to be let in and what traffic needs to be let out by using access lists (in the same way that Cisco IOS uses access lists). However, CBAC access lists include ip inspect statements that allow the inspection of the protocol to make sure that it is not tampered with before the protocol goes to the systems behind the firewall. Prerequisites Requirements There are no specific requirements for this document. Components Used This document is not restricted to specific software and hardware versions. Conventions For more information on document conventions, refer to the Cisco Technical Tips Conventions . Background Information CBAC can also be used with Network Address Translation (NAT), but the configuration in this document deals primarily with pure inspection. If you ...

Introduction In multicast VLAN networks, subscribers to a multicast group can exist in more than one VLAN. If the VLAN boundary restrictions in a network consist of Layer 2 switches, it might be necessary to replicate the multicast stream to the same group in different subnets, even if they are on the same physical network. Multicast VLAN Registration (MVR) routes packets received in a multicast source VLAN to one or more receive VLANs. Clients are in the receive VLANs and the multicast server is in the source VLAN. Multicast routing has to be disabled when MVR is enabled. Refer to the configuration guide at Understanding Multicast VLAN Registration for more information on MVR. This document provides a simple topology: a stack of Catalyst 3750 Switches with multicast source/receivers connected to it, a working configuration, and output of commands to verify whether the MVR works or not when a stream is sending. Prerequisites Requirements There are no s...

MRM Multicast Routing Monitor (MRM) facilitates automated fault detection in a large multicast routing infrastructure. MRM is designed to alert a network administrator of multicast routing problems near to real-time. MRM has two components: MRM tester and MRM manager. MRM tester is a sender or receiver. MRM is available in Cisco IOS Software Release 12.0(5)T and later. Only the MRM testers and managers need to be running the MRM-supported Cisco IOS version. Test Sender Configuration interface Ethernet0 ip mrm test-sender Test Receiver Configuration interface Ethernet0 ip mrm test-receiver Test Manager Configuration ip mrm manager test1 manager e0 group 239.1.1.1 senders 1 receivers 2 sender-list 1 access-list 1 permit 10.1.1.2 access-list 2 permit 10.1.4.2 Output from the show ip mrm manager command on Test Manager is shown here: Test_Manager# show ip mrm manager Manager:test1/10.1.2.2 is not running Beacon interval/hold...

Pragmatic General Multicast (PGM) is a reliable multicast transport protocol for applications that require ordered, duplicate-free, multicast data delivery from multiple sources to multiple receivers. PGM guarantees that a receiver in the group either receives all data packets from transmissions and retransmissions or can detect unrecoverable data packet loss. There are no PGM global commands. PGM is configured per interface with the ip pgm command. You must enable Multicast routing on the router with PIM on the interface.

There are two types of BPDU's: configuration BPDU's (c-BPDU) and topology change BPDU's (tcn-BPDU). Designated Bridges generate c-BPDU's. Root Ports and BLocked Ports listen for c-BPDU's. c-BPDU's originate from the root bridge and flow out towards the edge of the spanning tree, c-BPDU's are re-generated at every bridging device that receives them. tcn-BPDU's originate from root ports and flow towards the Root Bridge. c-BPDU's are the heartbeat of the Spanning Tree, tcn-BPDU's are the heart attack of the spanning tree.

今天晚上接到一位老同事來電詢問Private VLAN相關的問題，所以我上網找了一篇比較清楚簡單的說明摘錄如下，其中最容易讓大家confused的就是Private VLAN中包含了三種port，我用比較簡單的中文列出它們之間的不同點：   Promiscuous - 在這種Port上通常連結的是這個VLAN中的共用設備，如Gateway或是外部Server Isolated - 在這種Port上通常只能連結至Promiscuous ports，如果在IDC中提供主機代管服務，為了節省IP若是不想切割子網路造成無謂的IP浪費，可以在不同客戶主機使用同一個VLAN(使用同網段IP)但是彼此之間互不相通時就很適合使用這種Port Community - 在這種Port的設備可以直接與相同Community Port上的其他設備互通(比方說某客戶要求三台主機代管，這三台主機使用同網段IP又要互連，但是不跟同網段其他客戶主機互連)，也可以連結至 Promiscuous ports上的Gateway或是外部Server Private VLANs (PVLANs) Until now, I thought PVLANs were a bit  difficult to understand and to implement, like when studying to CCNP that took me a while to digest, and I had some doubts about it, till today! Man... how simple it is, and there´s no much "magic" in that (like our friend Scott Morris usually says)!  Pretty straight-forward and no big deals! The Security Video IPExpert is AWESOME. It´s short, informative, to the point, and solved MANY questions I´ve for a while in minutes! Man! What a nice way to do...