Gateway Load-Balancing protocol (GLBP)
Let’s take a look of HSRP and VRRP both provide gateway
resiliency with per-subnet load balancing, the upstream bandwidth of the
standby members
Gateway Load-balancing Protocol GLBP is Cisco proprietary
protocol, GLBP allow dynamic selection and simultaneous use of multiple
available routers gateways, and also permit automatic failover between those
gateways. Multiple routers share the load of frames that, from a client perspective,
are sent to a single default gate way address, with GLBP you can fully utilize
resources.
(In short)
GLBP Gateway load-balancing protocol is providing redundancy
gateway and true load balancing. GLBP allow a mechanism of four routers in each
forwarding group. By default, the active router directs the traffic from host
to each successive router in the group using Round-Robin algorithm.
GLBP Functions
·
Active Virtual Gateway (AVG): Member of a group elects
one gateway to be the AVG for the group, and the other group member provide backup
for the AVG in the event of AVG failure. AVG assign a different virtual MAC
addresses to each member of the GLBP group.
·
Active Virtual Forwarder Each
gateway assume to the responsibility for forwarding packets that are sent to
the virtual MAC address assigned to that gateway AVG. these gateways are called
AVF for their virtual MAC address.
·
GLBP communication GLBP members communicate
between each other through hello messages sent every 3 seconds to the multicast
address 224.0.0.102, User Datagram Protocol (UDP) port 3222.
GLBP provides upstream
load-sharing by utilizing the redundant uplinks simultaneously. It uses link
capacity efficiently, thus providing solid peak-load traffic coverage. By making
use of multiple available paths upstream from router or layer 3 switch running
GLBP, you can reduce output queues.
GLBP Features
·
Load-sharing we can configure GLBP so that
traffic from LAN client is shared by multiple routers. Load sharing distributes
the traffic load among available routers.
·
Multiple virtual routers GLBP supports up to
1.024 virtual routers as GLBP groups on each routers physical interface and up
to four virtual forwarders per group.
·
Preemption GLBP allow us to preempt an AVG
router with a higher-priority backup virtual gateway that has become available.
Forwarder preemption works in a similar way, except weighting instead of
priority and is enabled by default.
·
Efficient resource utilization: GLBP makes it possible
for any router in a group to serve as a backup, which eliminates the need for a
dedicated backup router because all available routers can support network
traffic.
GLBP Balancing host traffic
GLBP balances the traffic using the round –robin algorithm:
- · When a host send an ARP message for the gateway IP address, the AVG return the virtual MAC address of one of the AVFS.
- · When a second host sends an ARP message, the AVG return the next virtual MAC address from list.
Remember that each GLBP router will be the designated AVF
for the specific virtual MAC address that’s been assigned to it.
GLBP configuration:
Topology
GOAL:
·
Configure the basic IP addressing on routers as
per the diagram and test connectivity
·
Configure default route on R1/R3 to reach routes
on internet
·
Configure router 4 assume PC for verification in
the LAN
·
Configure static Route on R2-ISP back to LAN
network on both sides
·
Configure GLBP on R1 and R2 under F0/0
·
Make sure that R1 become AVG and R2 as AVF
·
Active Virtual Gateway priority 120 and the
other gateway is left at the default
·
Authentication between both switch MD5 password “internetwork”
·
The AVG should have the ability to resume the
Primary role once Primary router or track interface is reachable (preempt)
R1(config)#interface serial 3/0
R1(config-if)#ip address 10.1.1.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 192.168.1.100 255.0.0.0
R1(config-if)#no shutdown
R2(config)#interface serial 3/1
R2(config-if)#ip address 11.1.1.1 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 3/0
R2(config-if)#ip address 10.1.1.2 255.0.0.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface loopback 0
R2(config-if)#ip address 12.0.0.1 255.255.255.0
R2(config-if)#exit
R2(config)#interface loopback 1
R2(config-if)#ip address 12.0.1.1 255.255.255.0
R3(config)#interface serial 3/1
R3(config-if)#ip address 11.1.1.2 255.0.0.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface fastEthernet 0/0
R3(config-if)#ip address 192.168.1.200 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R4(config)#hostname client-R4
client-R4(config)#no ip routing
client-R4(config)#interface fastEthernet 0/0
client-R4(config-if)#ip address 192.168.1.1 255.255.255.0
client-R4(config-if)#no shutdown
R1(config)#ip route 0.0.0.0 0.0.0.0 10.1.1.2
R2(config)#ip route 192.168.1.0 255.255.255.0 10.1.1.1
R2(config)#ip route 192.168.1.0 255.255.255.0 11.1.1.2
R3(config)#ip route 0.0.0.0 0.0.0.0 11.1.1.1
R3#ping 192.168.1.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/58/96 ms
R1(config)#interface fastEthernet 0/0
R1(config-if)#glbp 1 authentication md5 key-string internetwork
R1(config-if)#glbp 1 preempt
R1(config-if)#glbp 1 timers 1 3
R1(config-if)#glbp 1 priority 120
R1(config-if)#glbp 1 ip 192.168.1.150
R3(config)#interface fastEthernet 0/0
R3(config-if)#glbp 1 authentication md5 key-string internetwork
R3(config-if)#glbp 1 preempt
R3(config-if)#glbp 1 timers 1 3
R3(config-if)#glbp 1 ip 192.168.1.150
R3#show glbp
FastEthernet0/0 - Group 1
State is Standby
1 state change, last state change 00:04:53
Virtual IP address is 192.168.1.150
Hello time 1 sec, hold time 3 sec
Next hello sent in 0.512 secs
Redirect time 600 sec, forwarder time-out 14400 sec
Authentication MD5, key-string
Preemption enabled, min delay 0 sec
Active is 192.168.1.100, priority 120 (expires in 2.560 sec)
Standby is local
Priority 100 (default)
Weighting 100 (default 100), thresholds: lower 1, upper 100
Load balancing: round-robin
Group members:
ca01.1ec4.0000 (192.168.1.100) authenticated
ca03.33a8.0000 (192.168.1.200) local
There are 2 forwarders (1 active)
Forwarder 1
State is Listen
MAC address is 0007.b400.0101 (learnt)
Owner ID is ca01.1ec4.0000
Time to live: 14399.424 sec (maximum 14400 sec)
Preemption enabled, min delay 30 sec
Active is 192.168.1.100 (primary), weighting 100 (expires in 2.656 sec)
Forwarder 2
State is Active
1 state change, last state change 00:04:55
MAC address is 0007.b400.0102 (default)
Owner ID is ca03.33a8.0000
Preemption enabled, min delay 30 sec
Active is local, weighting 100
R1#show glbp
FastEthernet0/0 - Group 1
State is Active
1 state change, last state change 00:09:31
Virtual IP address is 192.168.1.150
Hello time 1 sec, hold time 3 sec
Next hello sent in 0.800 secs
Redirect time 600 sec, forwarder time-out 14400 sec
Authentication MD5, key-string
Preemption enabled, min delay 0 sec
Active is local
Standby is 192.168.1.200, priority 100 (expires in 2.912 sec)
Priority 120 (configured)
Weighting 100 (default 100), thresholds: lower 1, upper 100
Load balancing: round-robin
Group members:
ca01.1ec4.0000 (192.168.1.100) local
ca03.33a8.0000 (192.168.1.200) authenticated
There are 2 forwarders (1 active)
Forwarder 1
State is Active
1 state change, last state change 00:09:28
MAC address is 0007.b400.0101 (default)
Owner ID is ca01.1ec4.0000
Redirection enabled
Preemption enabled, min delay 30 sec
Active is local, weighting 100
Forwarder 2
State is Listen
MAC address is 0007.b400.0102 (learnt)
Owner ID is ca03.33a8.0000
Redirection enabled, 599.936 sec remaining (maximum 600 sec)
Time to live: 14399.936 sec (maximum 14400 sec)
Preemption enabled, min delay 30 sec
Active is 192.168.1.200 (primary), weighting 100 (expires in 3.136 sec)
R1#show glbp brief
Interface Grp Fwd Pri State Address Active router Standby router
Fa0/0 1 - 120 Active 192.168.1.150 local 192.168.1.200
Fa0/0 1 1 - Active 0007.b400.0101 local -
Fa0/0 1 2 - Listen 0007.b400.0102 192.168.1.200 -
R3#show glbp brief
Interface Grp Fwd Pri State Address Active router Standby router
Fa0/0 1 - 100 Standby 192.168.1.150 192.168.1.100 local
Fa0/0 1 1 - Listen 0007.b400.0101 192.168.1.100 -
Fa0/0 1 2 - Active 0007.b400.0102 local -
client-R4#show ip arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 192.168.1.1 - ca04.3054.0000 ARPA FastEthernet0/0
client-R4#clear arp-cache
client-R4#ping 192.168.1.150
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.150, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/222/1016 ms
client-R4#show ip arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 192.168.1.1 - ca04.3054.0000 ARPA FastEthernet0/0
Internet 192.168.1.150 0 0007.b400.0101 ARPA FastEthernet0/0
client-R4#traceroute 12.0.0.1
Type escape sequence to abort.
Tracing the route to 12.0.0.1
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.1.100 112 msec 44 msec 36 msec
2 10.1.1.2 76 msec 116 msec 124 msec
Now shutdown R-2 F0/0 interface to check the redundancy
R1(config)#interface fastEthernet 0/0
R1(config-if)#shutdown
client-R4#traceroute 12.0.0.1
Type escape sequence to abort.
Tracing the route to 12.0.0.1
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.1.200 12 msec 44 msec 44 msec
2 11.1.1.1 60 msec 80 msec 68 msec
R3#show glbp
FastEthernet0/0 - Group 1
State is Active
2 state changes, last state change 00:04:17
Virtual IP address is 192.168.1.150
Hello time 1 sec, hold time 3 sec
Next hello sent in 0.320 secs
Redirect time 600 sec, forwarder time-out 14400 sec
Authentication MD5, key-string
Preemption enabled, min delay 0 sec
Active is local
Standby is unknown
Priority 100 (default)
Weighting 100 (default 100), thresholds: lower 1, upper 100
Load balancing: round-robin
Group members:
ca03.33a8.0000 (192.168.1.200) local
There are 2 forwarders (2 active)
Forwarder 1
State is Active
1 state change, last state change 00:04:17
MAC address is 0007.b400.0101 (learnt)
Owner ID is ca01.1ec4.0000
Redirection enabled, 338.912 sec remaining (maximum 600 sec)
Time to live: 14138.912 sec (maximum 14400 sec)
Preemption enabled, min delay 30 sec
Active is local, weighting 100
Forwarder 2
State is Active
1 state change, last state change 00:19:57
MAC address is 0007.b400.0102 (default)
Owner ID is ca03.33a8.0000
Redirection enabled
Preemption enabled, min delay 30 sec
Active is local, weighting 100
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