standby me...

hsrp keep it simple...

make a standby group and call it 1... set it on the redundant vlans between the dsw's... make sure the standby ip and group are the same, as below...


dsw1#sh run int vlan 10
Building configuration...

Current configuration : 84 bytes
!
interface Vlan10
 ip address 10.2.1.1 255.255.255.0
 standby 1 ip 10.2.1.100
end


dsw2#sh run int vlan 10
Building configuration...

Current configuration : 84 bytes
!
interface Vlan10
 ip address 10.2.1.2 255.255.255.0
 standby 1 ip 10.2.1.100
end


dsw2#sh standby
Vlan10 - Group 1
  State is Standby
    1 state change, last state change 00:08:20
  Virtual IP address is 10.2.1.100
  Active virtual MAC address is 0000.0c07.ac01
    Local virtual MAC address is 0000.0c07.ac01 (v1 default)
  Hello time 3 sec, hold time 10 sec
    Next hello sent in 0.052 secs
  Preemption disabled
  Active router is 10.2.1.1, priority 100 (expires in 9.948 sec) "vlan 10 on dsw1"
  Standby router is local
  Priority 100 (default 100)
  IP redundancy name is "hsrp-Vl10-1" (default)

i then took down the the vlan 10 interface on dsw1 so dsw2 took over...


dsw2#sh standby
Vlan10 - Group 1
  State is Active
    2 state changes, last state change 00:01:40
  Virtual IP address is 10.2.1.100
  Active virtual MAC address is 0000.0c07.ac01
    Local virtual MAC address is 0000.0c07.ac01 (v1 default)
  Hello time 3 sec, hold time 10 sec
    Next hello sent in 1.664 secs
  Preemption disabled
  Active router is local
  Standby router is unknown
  Priority 100 (default 100)
  IP redundancy name is "hsrp-Vl10-1" (default)

there is not another standby in the group so it is unknown... the client with the default gateway 10.2.1.1

will no longer be able to ping through to r3
lo0 3.3.3.3... its default gateway
has to be changed to the virtual
router address 10.2.1.100...

that is an important point about the default gateway...
this is how hsrp works...

hsrp...

with hsrp,  routers can give the illusion of a single virtual router to hosts on a lan.  this is called a standby group.  one router is elected from the group to forward packets that are sent by the hosts; this is the active router. if the active router fails, a standby router will then forward packets in its stead.  although there may be more than two routers participating in the group (the virtual router), only the active router at any given time will actually forward packets.

once a router has been elected active, only the active and standby routers send periodic hello packets.  of course,  if the standby router then fails, another election commences.

routers may belong to more than one standby group, and hellos are kept separate between the groups.

each group has a single well known mac-address and ip address.

hsrp uses the well known mac-address

0000.0c07.acXX

where XX is the group number (ac01 ie. is group 1)