Cisco Nexus 7000 Series - HSRP Versions

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19-3
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
OL-20002-02
Chapter 19 Configuring HSRP
Information About HSRP
Figure 19-1 HSRP Topology With Two Enabled Routers
The virtual router does not physically exist but represents the common default router for interfaces that
are configured to provide backup to each other. You do not need to configure the hosts on the LAN with
the IP address of the active router. Instead, you configure them with the IP address (virtual IP address)
of the virtual router as their default router. If the active router fails to send a hello message within the
configurable period of time, the standby router takes over, responds to the virtual addresses, and becomes
the active router, assuming the active router duties. From the host perspective, the virtual router remains
the same.
Note In Cisco NX-OS Release 4.1(2) and later, packets received on a routed port destined for the HSRP virtual
IP address will terminate on the local router, regardless of whether that router is the active HSRP router
or the standby HSRP router. This includes ping and telnet traffic. Packets received on a Layer 2 (VLAN)
interface destined for the HSRP virtual IP address will terminate on the active router.
HSRP Versions
Cisco NX-OS supports HSRP version 1 by default. You can configure an interface to use HSRP version
2.
HSRP version 2 has the following enhancements to to HSRP version 1:
• Expands the group number range. HSRP version 1 supports group numbers from 0 to 255. HSRP
version 2 supports group numbers from 0 to 4095.
• Uses the new IP multicast address 224.0.0.102 to send hello packets instead of the multicast address
of 224.0.0.2, which is used by HSRP version 1.
• Uses the MAC address range from 0000.0C9F.F000 to 0000.0C9F.FFFF. HSRP version 1 uses the
MAC address range 0000.0C07.AC00 to 0000.0C07.ACFF.
• Adds support for MD5 authentication.
When you change the HSRP version, Cisco NX-OS reinitializes the group because it now has a new
virtual MAC address.
192.0.2.1
192.0.2.2
192.0.2.3
Active
router
Virtual
router
Standby
router
185061
Internet or
ISP backbone
Host A Host B
LAN
Host C Host D