Normally LDP neighbors are found automatically by sending UDP Hello packets on Port 646 with the destination of multicast address 188.8.131.52 out of each LDP enabled interface. In some MPLS applications a LDP session must be established between non directly connected peers to exchange labels. In such cases Hello packets can not be just broadcasted, instead these Hello packets are sent as unicast packets using UDP on port 646 and destined to the targeted peer. AToM and some Traffic Engineering scenarios are examples of these applications that require a targeted LDP session between non directly connected routers.Read More »
What Is ?
The IS-IS Routing Protocol may be used as an IGP to support IP as well as OSI. This allows a single routing protocol to be used to support pure IP environments, pure OSI environments, and dual environments. Integrated IS-IS is deployed extensively in an IP-only environment in the top-tier Internet service provider (ISP) networks. The IS-IS working group of the Internet Engineering Task Force (IETF) developed the specification for Integrated IS-IS (RFC 1195).Read More »
A voice VLAN port is an access port attached to a Cisco IP Phone, configured to use one VLAN for voice traffic and another VLAN for data traffic from a device attached to the phone. This feature allows the switch to use CDP for sending configuration options regarding COS, Voice VLAN and data VLAN to the IP Phone. This feature is disabled by default and the IP Phone sends both voice and data traffic in the default VLAN (VLAN 0). you can use CISCO documentation for more details about this feature.Read More »
BPDUs are the messages exchanged between switches to calculate the spanning tree topology. BPDU filter is a feature used to filter sending or receiving BPDUs on a switchport. It is extremely useful on those ports which are configured as portfast ports as there is no need to send or receive any BPDU messages on of these ports. BPDU filter can be configured globally or under the interface level. When configured globally all portfast enabled ports stop sending and receiving BPDUs, but if a BPDU is received on the port it gets out of the portfast state and normally participate in …Read More »
Extended VLANs are VLANs within the range of 1006 to 4094. They are mainly used in service provider networks to allow the provisioning of number of customers. In order to configure an extended VLAN you have to follow the guideline below: Extended VLANs are used just like normal VLANs; only different range. Extended VLANs must be configured on Switches that are in VTP Transparent mode only. Extended VLANs can not be configured using VLAN database mode (only configuration mode). Extended VLANs are saved in the configuration file. Configuration: SW1(config)#vtp mod transparent Setting device to VTP TRANSPARENT mode. SW1(config)#vlan 2001 !-- …Read More »
IP unnumbered is method that you can use to enable IP processing on a Point to Point interface without assigning an it an IP address to conserve the IP address space. All you need to do, is to select an interface that you are going to borrow its IP address; preferrably the loopback interface because it is always in the up state ,then use the command IP unnumbered <selected-interface> under the point to point interface. To summarize: This feature helps in conserving IPv4 addresses. Mostly used in dial-up or DSL setups. The IP unnumbered command must be used under a …Read More »