GLBP - Configure the Global Load Balancing Protocol

GLBP is different from HSRP and GLBP, as in - it's more complex and gives more possibilities, such as LoadBalancing
It's got 1 VIRTUAL IP, and VARIOUS MACs

!!!You can have UP TO 4 ROUTERS IN A GLBP GROUP!!!

GLBP Group Members communicate using HELLOs 224.0.0.102, UDP/3222, by default Hello Timer = 3 sec

Basically there are 2 roles:
- AVG (Active Virtual Gateway) MASTER Router in charge of Assigning Virtual MAC Addresses to other Routers
and it has to know ALL the MACs of the AVFs
- AVFs (Active Virtual Forwarders) the rest of the Routers, which take AVG function if AVG dies.

sh glbp br
Interface   Grp  Fwd Pri State    Address         Active router   Standby route
Fa0/0       1    -   100 Standby  10.1.1.100      10.1.1.2        local
Fa0/0       1    1   7   Active   0007.b400.0101  local           -
Fa0/0       1    2   7   Listen   0007.b400.0102  10.1.1.2        -

You can tune GLBP as you like, which means that (besides all the stuff you can also do in HSRP and VRRP) you can
choose the Load Balancing method:
ES-MAT-AES-SR03(config-if)#glbp 1 load-balancing ?
  host-dependent  Load balance equally, source MAC determines forwarder choice
  round-robin     Load balance equally using each forwarder in turn
  weighted        Load balance in proportion to forwarder weighting (GLBP places WEIGHT on each router)
  <cr>

As an additional GLBP feature, there is a REDIRECT timer, which sets the time-out for assigning the Virtual MAC
of AVF that has failed.
ES-MAT-AES-SR03(config-if)#glbp 1 timers ?
  <1-60>    Hello interval in seconds
  msec      Specify hello interval in milliseconds
  redirect  Specify time-out values for failed forwarders

TRACKing is also different on GLBP, as in - it's configured in the Global Configuration mode, with a global Track Object.
ADVANTAGE: You can track 2 interfaces at once!!!
ES-MAT-AES-SR03(config)#track 1 interface fa0/0 ?
  ip             IP parameters <- TO TRACK IP ROUTING
  line-protocol  Track interface line-protocol <- TRACK IF THE INTERFACE IS DOWN

(config)#track 1 interface fa0/0 line-protocol
(config-track)#track 2 interface s0/1/0 line-protocol

#show track
Track 1
  Interface FastEthernet0/1 line-protocol
  Line protocol is Up
    1 change, last change 00:02:39
Track 2
  Interface Serial0/1/0 line-protocol
  Line protocol is Up
    1 change, last change 00:02:10

Now the TRACK OBJECTS need to be applied to the Interface where GLBP is configured (If any of the tracked interfaces go DOWN, the WEIGHT will be decremented by 10, but these values can be tuned):
ES-MAT-AES-SR03(config-if)#glbp 1 weighting track  1 <-MEMORIZE as it's a bit NON-INTUITIVE
ES-MAT-AES-SR03(config-if)#glbp 1 weighting track  2