GLBP (Gateway Load Balancing Protocol)

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GLBP
If another device existed in the same GLBP group with a higher priority, then the device with the higher priority would be elected. If both devices have the same priority, the backup virtual gateway with the higher IP address would be elected to become the active virtual gateway.

PC1
hostname PC1
ip cef
interface Ethernet0/0
 ip address 12.0.0.5 255.255.255.0
ip route 0.0.0.0 0.0.0.0 12.0.0.1

R1
hostname R1
ip cef
key chain MYCHAIN
 key 1
  key-string c1$c0
interface Ethernet0/0
 ip address 12.0.0.2 255.255.255.0
 ip authentication mode eigrp 1 md5
 ip authentication key-chain eigrp 1 MYCHAIN
 glbp 1 ip 12.0.0.1
 glbp 1 authentication md5 key-chain MYCHAIN
interface Ethernet0/1
 ip address 23.0.0.2 255.255.255.0
router eigrp 1
 network 12.0.0.0 0.0.0.255
 network 23.0.0.0 0.0.0.255
 redistribute static

R2
hostname R2
ip cef
key chain MYCHAIN
 key 1
  key-string c1$c0
interface Ethernet0/0
 ip address 12.0.0.3 255.255.255.0
 ip authentication mode eigrp 1 md5
 ip authentication key-chain eigrp 1 MYCHAIN
 glbp 1 ip 12.0.0.1
 glbp 1 authentication md5 key-chain MYCHAIN
interface Ethernet0/1
 ip address 23.0.0.3 255.255.255.0
router eigrp 1
 network 12.0.0.0 0.0.0.255
 network 23.0.0.0 0.0.0.255

R3
hostname R3
ip cef
key chain MYCHAIN
 key 1
  key-string c1$c0
interface Ethernet0/0
 ip address 12.0.0.4 255.255.255.0
 ip authentication mode eigrp 1 md5
 ip authentication key-chain eigrp 1 MYCHAIN
 glbp 1 ip 12.0.0.1
 glbp 1 authentication md5 key-chain MYCHAIN
interface Ethernet0/1
 ip address 23.0.0.4 255.255.255.0
router eigrp 1
 network 12.0.0.0 0.0.0.255
 network 23.0.0.0 0.0.0.255

SVR1
hostname SVR1
interface Ethernet0/1
 ip address 23.0.0.5 255.255.255.0
ip route 0.0.0.0 0.0.0.0 23.0.0.1
ip route 12.0.0.0 255.255.255.0 23.0.0.2
ip route 12.0.0.0 255.255.255.0 23.0.0.3
ip route 12.0.0.0 255.255.255.0 23.0.0.4

R1#sh glbp br
Interface   Grp  Fwd Pri State    Address         Active router   Standby router
Et0/0       1    –   100 Listen   12.0.0.1        12.0.0.4        12.0.0.3
Et0/0       1    1   –   Listen   0007.b400.0101  12.0.0.4        –
Et0/0       1    2   –   Active   0007.b400.0102  local           –
Et0/0       1    3   –   Listen   0007.b400.0103  12.0.0.3        –

R1#sh glbp detail
Ethernet0/0 – Group 1
  State is Listen
  Virtual IP address is 12.0.0.1
  Hello time 3 sec, hold time 10 sec
    Next hello sent in 0.992 secs
  Redirect time 600 sec, forwarder timeout 14400 sec
  Authentication MD5, key-chain “MYCHAIN”
  Preemption disabled
  Active is 12.0.0.4, priority 100 (expires in 8.960 sec)
  Standby is 12.0.0.3, priority 100 (expires in 7.744 sec)
  Priority 100 (default)
  Weighting 100 (default 100), thresholds: lower 1, upper 100
  Load balancing: round-robin
  Group members:
    aabb.cc00.0100 (12.0.0.2) local
    aabb.cc00.0200 (12.0.0.3) authenticated
    aabb.cc00.0300 (12.0.0.4) authenticated
  There are 3 forwarders (1 active)
  Forwarder 1
    State is Listen
    MAC address is 0007.b400.0101 (learnt)
    Owner ID is aabb.cc00.0300
    Time to live: 14397.920 sec (maximum 14400 sec)
    Preemption enabled, min delay 30 sec
    Active is 12.0.0.4 (primary), weighting 100 (expires in 9.696 sec)
  Forwarder 2
    State is Active
      1 state change, last state change 00:22:32
    MAC address is 0007.b400.0102 (default)
    Owner ID is aabb.cc00.0100
    Preemption enabled, min delay 30 sec
    Active is local, weighting 100
  Forwarder 3
    State is Listen
    MAC address is 0007.b400.0103 (learnt)
    Owner ID is aabb.cc00.0200
    Time to live: 14397.760 sec (maximum 14400 sec)
    Preemption enabled, min delay 30 sec
    Active is 12.0.0.3 (primary), weighting 100 (expires in 9.024 sec)

PC1#traceroute 23.0.0.5
Type escape sequence to abort.
Tracing the route to 23.0.0.5
VRF info: (vrf in name/id, vrf out name/id)
  1 12.0.0.2 1 msec 3 msec 8 msec
  2 23.0.0.5 4 msec 3 msec *

PC2#traceroute 23.0.0.5
Type escape sequence to abort.
Tracing the route to 23.0.0.5
VRF info: (vrf in name/id, vrf out name/id)
  1 12.0.0.4 0 msec 1 msec 1 msec
  2 23.0.0.5 2 msec 2 msec *
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