Hot Standby Router Protocol (HSRP) provides redundancy for IP networks, ensuring that user traffic immediately and transparently recovers from first hop router failures. HSRP allows multiple routers on a single LAN to share a virtual IP and MAC address configured as the default gateway on the hosts. From the group of routers configured in an HSRP group, there is one router elected as the active router and another as a standby router. The active router assumes the role of forwarding packets sent to the virtual IP address. If the active router fails, the standby router takes over as the new active router. HSRP routers send HSRP packets to the multicast group address 126.96.36.199, to which all routers listen and elect the active and standby routers.
LAN Emulation (LANE) is a standard used to connect two different LAN segments across an ATM cloud. There are different components in LANE that emulate the nature of a broadcast capable LAN on an ATM network, which by itself does not support broadcasting. Since HSRP was designed for use over multicast or broadcast capable LANs, there are certain issues to be handled when running HSRP over LANE. These issues are automatically addressed by the Cisco IOS Software running on the devices.
In LANE, the devices acting as LANE Clients (LEC) establish ATM virtual circuits between them to exchange data traffic. To establish the virtual circuits, the destination MAC address of a host in the LAN frame must be mapped to an ATM Network Service Access Point (NSAP) address used by the LEC to which the destination host is attached. This is done through the LAN Emulation ARP (LE-ARP) process by using the services of a LAN Emulation Server (LES), which maintains this mapping when the LEC joins a particular Emulated LAN (ELAN). The MAC-to-NSAP address mapping obtained through the LE-ARP process is maintained in the LE-ARP table on the LECs.
When HSRP operates over LANE, the same virtual MAC address must be mapped to a new ATM NSAP address when a new router becomes the active router. The LE-ARP table must be updated on the LECs with the new information without waiting for the default timeout values which would otherwise defeat the purpose of redundancy provided by HSRP. These are different ways in which routers acting as HSRP devices are connected over an ATM network implementing LANE:
All HSRP routers directly connected to the ATM cloud functioning as an LEC
All HSRP routers connected to a LAN switch attached to the ATM cloud and functioning as a LANE client
A combination of both the above
To address the different HSRP over LANE scenarios, certain mechanisms have been introduced into the LANE specification to send additional messages and refresh the LE-ARP table. For more information, refer to Implementing HSRP Over LANE.
I will be replacing our existing campus network consisting of two Cisco Catayst 6807 XL chasis switches and 6800ia fex switches with new Catalyst 9500 switches to replace the 6807's and Catalyst 9300's in the closets replacing the 6800ia's. We are j...
“Catalyst 8500 Series - Deep Dive”
This event will have place on Tuesday 17th, November 2020 at 10hrs PDT
The Catalyst 8500 Series Edge Platforms are built with the highly programmable, third-generation Cisco Quantum Flow Processor and designed for ...
Hi to all, I have fan noise with my 2960XR (WS-C2960XR-48LPD-I), it come from his PSU (PWR-C2-640WAC).I try to make a video to ear noise, could you tell me if you have the same noise on your side ? I make a video here : (view in My Videos)P...
“Catalyst 8000 Edge Platforms Family Overview”
This event will have place on Wednesday 4th, November 2020 at 10hrs PDT
Designed for an intent-based networks, the Cisco Catalyst 8000 Edge Platforms family offers best-in-class networking and security ...