1 -
Hot Standby Redundancy Protocol(HSRP)
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HSRP is Cisco’s standard method
of providing high network availability by providing first-hop redundancy for IP hosts on an IEEE 802 LAN configured
with a default gateway IP address.
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Main purpose; protect to
Default Gateway.
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Routers are share Virtual IP Address
and Virtual Mac Address. Mac Address’s last 2 digit= HSRP Group Identifier.
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There is no load balancing.
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Active – Standby mode
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Router’s Higher Ip
Address=Active Lower Ip address=Standby
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We change the HSRP priority for select the
active Backbone. Default priority = 100
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Hello packets = 3 sec Dead time
= 10 sec
HSRP Preemption:
Force the router to a new HSRP process. When active router turned off, standy router change to active router. After
that; when active router turned on, standby router will continue to work
active. Preemption command provide if active router turn on again, the router
is active again.
HSRP Modes:
Initial: It can be see
the HSRP run or not running.
Learn: Router
doesnt have any virtual ip, there isn’t any authentication hello packet
from active router.
Listen: Virtual
ip is okey, routers dont certain active or standby
Speak: Periodic
hello packets, routers know active and standby mode.
Standby:
Standby mode
Active: Active
mode
Multigroup HSRP: It’s create a Vlan ip address’s HSRP.
HSRP Interface Tracking: If there are some problems routers WAN port, this command will follow the
WAN port. If there is a problem with wan port in active router, standby’s wan
port will be active.
Object Tracking: Check the routers behind wan port.
HSRP Authenticton: Plain Text and MD5.
HSRP Configuration
Router(config)# int gig 0/0
Router(config-if)# ip address 172.16.30.2 255.255.255.0
Router(config-if)# standby 1 ip 172.16.30.1 (virtual ip address)
Router(config-if)# standby 1 priorty 150 (for work active mode)
Router(config-if)# standby 1 preempt (if turn off the router, turn on again
it can be work active mode.)
Router_2(config)# int gig 0/0
Router_2(config-if)# ip address 172.16.30.3 255.255.255.0
Router_2(config-if)# standby 1 ip 172.16.30.1
Multigroup HSRP Config
Router(config)# spanning-tree vlan 10 root secondary
Router(config)# spanning-tree vlan 20 root primary
Router(config)# int vlan 10
Router(config-if)# ip address 10.1.10.3 255.255.255.0
Router(config-if)# standby 10 ip 10.1.10.1
Router(config-if)# standby 10 priortiy 90
Router(config-if)# standby 10 preempt
Router(config-if)#exit
Router(config)# int vlan 20
Router(config-if)# ip address 10.1.20.3 255.255.255.0
Router(config-if)# standby 20 ip 10.1.20.1
Router(config-if)# standby 20 priorty 110
Router(config-if)# stanby 20 preempt
Interface Group Tracking
Router(config)# int gig 0/0
Router(config-if)# ip address 192.168.100.2
255.255.255.0
Router(config-if)# standby 1 ip 192.168.100.1
Router(config-if)# standby 1 preempt
Router(config-if)# stanby track serial 0/1 (follow wan port)
(this command will write another router)
GLBP(Gateway Load Balancing Protocol)
- Automatic
and simultaneous use of multiple gateways.
-The
Gateway Load Balancing Protocol feature provides automatic router backup for IP
hosts configured with a single default gateway on an IEEE 802.3 LAN.
-Failover
between gateways.
-GLBP
provides load balancing over multiple routers (gateways) using a single virtual
IP address and multiple virtual MAC addresses.
-Each
host is configured with the same virtual IP address, and all routers in the
virtual router group participate in forwarding packets
-Best
proporties; Load Balancing
-Using
UDP
-L3
redundancy
-Traffic
can be shared in both directions.
-Hello
packet = 3 sec ; Dead Time = 10 sec
-Mac
Address: 0007.44XX.XXYY XXXX: 64 bit zero and 10 bit GLBP number
What is the difference of
GLBP and HSRP?
Two GLBP Modes:
1- Active Virtual Gateway
2- Active Virtual Forwarding (Max 4 AVF)
Active Virtual Gateway:
- The AVG assigns a virtual MAC address to each member of the GLBP group
- Each gateway assumes responsibility for forwarding packets sent to the virtual MAC address assigned to it by the Active Virtual Gateway.
- The Active Virtual Gateway is responsible for answering Address Resolution Protocol (ARP) requests for the virtual IP address. Load sharing is achieved by the AVG replying to the ARP requests with different virtual MAC addresses.
- A GLBP group allows up to four virtual MAC addresses per group. The AVG is responsible for assigning the virtual MAC addresses to each member of the group.
Active Virtual Forwarding:
- We can use max 4 AVF.
- Transmits packets sent to the virtual mac address provided by AVF.
GLBP operates virtual gateway redundancy in the same way as HSRP.
Notes: If Active Virtual Gateway router becomes unavailable, clients will not lose Access to WAN because Active Virtual Forwarding router will assume responsibility for forwarding packets sent to the virtual MAC address of Router A, and for responding to packets sent to its own virtual MAC address. Router B will also assume the role of the AVG for the entire GLBP group.
Disable: There is no Virtual Ip Address
Initial: Virtual Ip Address Ok, Config is not yet complete.
Listen: Transmit to hello packet
Speak: Try to be active or standby(avg or avf)
Standby: If there are some problems from active router, it is ready for be active.
Active: Responding to arp request.
GLBP Benefits
Load Sharing
You can configure GLBP in such a way that traffic from LAN clients can be shared by multiple routers, thereby sharing the traffic load more equitably among available routers.
Multiple Virtual Routers
GLBP supports up to 1024 virtual routers (GLBP groups) on each physical interface of a router, and up to 4 virtual forwarders per group.
Preemption
The redundancy scheme of GLBP enables you to preempt an active virtual gateway with a higher priority backup virtual gateway that has become available. Forwarder preemption works in a similar way, except that forwarder preemption uses weighting instead of priority and is enabled by default.
Authentication
You can use a simple text password authentication scheme between GLBP group members to detect configuration errors. A router within a GLBP group with a different authentication string than other routers will be ignored by other group members.
GLBP Gateway Weighting and Tracking
GLBP uses a weighting scheme to determine the forwarding capacity of each router in the GLBP group. The weighting assigned to a router in the GLBP group determines whether it will forward packets and, if so, the proportion of hosts in the LAN for which it will forward packets. Thresholds can be set to disable forwarding when the weighting falls below a certain value, and when it rises above another threshold, forwarding is automatically reenabled.
The GLBP group weighting can be automatically adjusted by tracking the state of an interface within the router. If a tracked interface goes down, the GLBP group weighting is reduced by a specified value. Different interfaces can be tracked to decrement the GLBP weighting by varying amounts.
GLBP
Configuration
R1:int
f0/0
R1:
glbp 123 ip 10.1.1.254
R1:
glbp 123 priority 120
R1:
glbp 123 preempt
R2:
int f0/0
R2:
glbp 123 ip 10.1.1.254
R2:
glbp 123 priority 110
R2:
glbp 123 preempt
R3:
int f0/0
R3:
glbp 123 ip 10.1.1.254
Verify
to GLBP configuration “Show ip glbp brief”
Mac-address
assigined by R1
Highest
priority select AVG. Default load-balancing Round-Robin.
With
round-robin, AVG will reply each ARP request for the GLBP virtual IP with each
AVF’s virtual MAC address in turns, so all AVFs will be used equally.
GLBP
Weighted Configuration
Weighted
algorithm distribute traffic to each AVF based on the weight value assigned to
them. An AVF with bigger weight value will get more traffic redirected to it.
For
example, if we assign weight value 1 for R1, 1 for R2, and 2 for R3, then AVG
will reply ARP requests for the GLBP virtual IP address using R3’s virtual MAC
address two times more often than using R1’s or R2’s. The configuration command
for the above example scenario is as follows:
R1:
int f0/0
R1:
glbp 123 load-balancing weighted
R1:
glbp 123 weight 1
R2:
int f0/0
R2:
glbp 123 load-balancing weighted
R2:
glbp 123 weight 1
R3:
int f0/0
R3:
glbp 123 load-balancing weighted
R3:
glbp 123 weight 2
Host Dependant Algorithm
Host-dependent
algorithm guarantees that the same gateway will always be used for a specific
client, as long as there is no changes on the AVF number. Under some situations
this approach could be the best option, for example in case of stateful NAT.
R1:
int f0/0
R1:
glbp 123 load-balancing host-dependant
Repeat
the same command R2 and R3.
If
we try traceroute via Client B or Client C we would probably got different
gateway than Client A, but each client will keep redirected using the same
gateway until there is a change on AVF number.
