cisco 300-320 dumps pdf

cisco 300-320 dumps pdf.Problems with user devicesIn most campus environments, only a default gateway IP address is assigned to the endpoint (this is usually assigned via DHCP). In this environment, if the routing device (the default gateway) fails, the endpoint will not be able to access network devices outside of its VLAN. Unfortunately, this implementation does not provide redundancy because the endpoint can only be configured with one default gateway address (either assigned via DHCP or statically).18.4.2 Hot Standby Router ProtocolHSRP is a Cisco-specific protocol that allows the endpoint to define only a single default gateway while providing Layer 3 redundancy, overcoming the problems that exist with IRDP, proxy ARP, and the use of routing protocols at the endpoint. Unlike the four solutions described earlier, HSRP is completely transparent to the endpoint and requires no additional configuration on the endpoint. HSRP allows Cisco routing devices to monitor each other's status, which allows for very fast failover in the event of a primary default gateway failure. This is achieved by creating HSRP groups.In HSRP, a group of routing devices forms a single virtual default gateway. This virtual default gateway has a virtual IP address and a virtual MAC address; if the primary routing device fails, another routing device in the HSRP group takes over and processes the frames sent by the endpoint to the virtual MAC address.The advantage of HSRP groups is that different subnets (VLANs) can use different default gateways, thus achieving load balancing. In addition, in each HSRP group, there is a primary default gateway, while multiple routers can be allowed to take on standby roles. Each routing device can have up to 256 standby groups, thus providing 255 default gateways. A routing device can act as a standby for multiple primary default gateways. Each standby group tracks the primary routing device - the device that is currently forwarding frames sent to the virtual MAC address. Note that when using HSRP, only one routing device actually forwards traffic.One advantage of HSRP is that it can be customized to fit the size of your network. For example, if you have a VLAN with 1000 devices, you can configure two HSRP groups: each group is responsible for 500 devices. Then, assign routing devices to each group. For example, if you have only two routing devices, you can have the first routing device act as the RP for group 1 and the backup router for group 2, and have the second routing device act as the backup router for group 1 and the RP for group 2. This allows both routing devices to forward traffic, while providing redundancy - the failure of the active routing device in one of the groups, the other routing device will elevate itself to the active state.How HSRP WorksAs stated in the previous section, in an HSRP group, only one routing device actually forwards traffic. By using a priority scheme, one routing device is elected as the forwarding router, while the other routing devices act as standby routers. The default priority of a routing device is 100, but it can be modified. The routing device with the highest priority in the group is elected as the active router, while the other routing devices are in a standby state. The active routing device responds to ARP requests from endpoints by providing the virtual MAC address of the HSRP group.Each HSRP group must have a unique virtual IP address and virtual MAC address, which means that these addresses are different for each group. The virtual MAC address is 0000.0c07.acXX, where 0000.0c is the Cisco vendor code, 07-ac is the famous HSRP address, and XX is the HSRP group number (in hexadecimal). o Because the virtual MAC address is unique, the HSRP group number must be unique in order to ensure that the virtual MAC address is unique.