Notebook – HSRP, VRRP, & GLBP

Yes, I’m finally back with more notes that I have been accumulating. I will be posting my notes from time to time, making changes to them over time. Don’t take these notes as a learning source! They’re notes! And most of the time they aren’t even complete!

HSRP, VRRP, GLBP [Not Complete]
HSRP - Hot StandBy Router Protocol
-Created by Cisco, 1994 Proprietary
-Uses a default hello timer of 3 seconds with a hold of 10
.Gateways organized into standby groups
.One gateway active, others in standby
.Virtual router IP and MAC address generated
.Hello/3s , Dead/10s
Both gateways will have their own IPs, but the standby group will have one ip address assigned to it but it will generate a virtual mac address.
Virtual MAC address is generated according to ID's:
         [0000.0C] |[07.AC]    |[xx]                 |
   Cisco Vendor ID |HSRP ID    |Standby Group Number |
Clients will use that standby group IP address as their default IP address. This means nothing on the client end of the connection needs to change if one gateway fails.
Gateways will send an ARP message to any downstream switches to have traffic redirected in the right path.
VRRP - Virtual Router Redundancy Protocol
-Created by IETF, 1999
-Open Standard, not proprietary
-Has faster timers than HSRP - Hello 1 seconds, Hold Time 3 seconds
Skew Timer - a timer that starts after a hello is missed + the hold time.
Uses Master and Backup
Stanby Group is called the VRRP Group
Master Router can share virtual IP
If a master sees one of it's tracked interfaces go down it will automtically set it's priority to 0.
GLBP - Gateway Load Balancing Protocol
-Created by Cisco, 2005 Proprietary
-Identical to HSRP but allows active/active connection that enables load balancing.
-GLBP uses as the multicast IP to send/listen for hello packets
-GPBP elects on AVG for each group.
GLBP will use a single IP with Multiple MAC addresses.
Can use Equal or Unequal load balancing.
GLBP will have one single Active Virtual Gateway - Manages the MAC address pools, knows about all other virtual MACs and which ones are assigned to backup routers.
It will respond to ARP requests but will respond with it's Virtual MAC or another router's virtual MAC depending on how load balancing is configured.
Other routers in a GLBP domain will be labeled as Active Virtual Forwarders.
To Setup HSRP:
Create a Standby Group
Select a Primary and a Standby Device.
(Make sure you have a link between the two switches/routers)
Go into the chosen int vlan:
switch(config)#int vlan 25
switch(config-if)#standby group 1 ip
(ip is the virtual IP)
switch(config-if)#standby 1 priority 150
routers will have a default of 100.
Higher priority # = higher priority. Higher # will make the switch/router the active router.
Do this same configuration on the other switch/router. However with a lower priority.
show standby - will show standby group statistics

Premption - When a higher priority routers comes back online or is reconverged to a standby group, it tells the other router it will take over as the primary.
Sometimes not a good idea because flapping links/unstable primary (i.e. constant reboots, or hardware failure) will cause outage from deactivating the standby switch/router constantly.
switch(config)#int vlan 25
switch(config-if)#standby 1 preempt (overthrow lower priority designated routers)
Tracking - if a WAN link on the active router fails, it will automatically decrease it's priority number in order to force standby into active. Preempt must be configured.
switch(config-if)#standby 1 track fastEthernet 0/24 50 (reduce priority by 50)
You can set prempt delay using the <minimum swtich>
switch(config-if)#standby 1 prempt delay 90 (wait 90 seconds)
Change timers:
switch(config-if)#standby 1 timers (hello) (dead)
To Setup HSRP:
Configure VRRP Group
switch(config)#int g0/24
switch(config-if)#vrrp 10 ip
switch(config-if)#vrrp 10 timers advertise (this will advertise to the other backup the hello timer)
no dead time is set because dead time is default x3 the hello timer.
Other switch/router will have a similar configuration
To Configure GLBP:
switch(config)#int g0/24
switch(config-if)#glbp 1 ip (1 is the group number)
switch(config-if)#glbp 1 priority 1-255 (this will elect the AVG, everything else will be the AVF)
switch(config-if)#glbp 1 timers
switch(config-if)#glbp load-balancing (by default uses round-robin method)
host-dependent - load balance equally, source mac determines forwarder choice
weighted - load balance in proportion to forwarder weighting - 1 - 254 / track

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